Dermatology Module August 2023 MRCP Part-1

Hint

This lady has tuberous sclerosis, which is inherited in autosomal dominant fashion, with responsible defects having been identified on both chromosome 9 and chromosome 16. These chromosomes carry codes for hamartin and tuberin, protein gene products which are responsible for regulation of cell growth.

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Most of the tumours which are produced in tuberous sclerosis are hamartomas, and various phenotypes of the disease occur, with some parents of patients having much more subtle features than those seen in their children.

Hint

Exacerbation or localisation of other dermatoses is characteristic of:

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• Pellagra

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• Hartnup disease

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• Lupus erythematosus

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• Darier’s disease

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• Rosacea

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• Scleroderma

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• Actinic lichen planus

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• Lymphocytoma.

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Hint

The most important adverse event of infliximab is the increased risk of infection including sepsis and opportunistic infection. Patients with predisposing underlying conditions such as diabetes mellitus are at higher risk of infection. If any severe infection develops infliximab should be temporarily withdrawn and the need for antibiotics considered.

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All tumour necrosis factor (TNF) blockers carry a warning about reactivation of tuberculosis (TB) (black box for infliximab). The boxed warning advises prescribing physicians to screen all patients for tuberculosis (TB) before initiation of therapy, to pretreat those with latent disease and to monitor patients for signs and symptoms of tuberculosis (TB) throughout the treatment course with infliximab. In a recent review of 130 cases of infliximab-associated tuberculosis reported to the FDA, many cases occurred in patients with a negative tuberculin skin test but with risk factors for tuberculosis (TB). Most cases occur shortly after initiation of treatment. Presentation may be with disseminated or military tuberculosis. A screening chest x-ray is essential and testing for tuberculid sensitivity should be considered.

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Etanercept, which is a recombinant tumour necrosis factor and receptor fusion protein, has demonstrated considerable beneficial effects on psoriatic arthropathy in placebo controlled, double blind studies.

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Part of the attraction of vitamin D analogues over steroids is that they do not cause cutaneous atrophy, whereas steroids do.

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Retinoids are most effective in combination therapy especially with ultraviolet B (UVB) phototherapy and PUVA but as monotherapy they are not effective treatment for psoriasis.

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Psoralen and ultraviolet light (PUVA) is an effective treatment for psoriasis, but this has been related to increased risk of squamous cell carcinoma and possibly malignant melanoma.

Hint

The prevalence of psoriasis is reported as between 0.5 and 4.6%.

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For reasons which may be explained by the filtering of ultraviolet B (UVB) light, psoriasis is more common at higher altitudes.

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The commonest form of psoriasis is plaque psoriasis, making up approximately 80% of cases (guttate -10%, erythrodermic – 3%, pustular – 3%).

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Studies report:

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• a 5-42% prevalence of psoriatic arthropathy in patients with cutaneous psoriasis 

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• arthropathy precedes cutaneous lesions in 20%

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• cutaneous lesions precede joint disease in 60-70%, and

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• they occur simultaneously in 10-20%.

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Hint

Neurofibromatosis 1 (NF1) is usually diagnosed during childhood. Signs are often noticeable at birth or shortly afterward and almost always by age of 10 years. Signs and symptoms are often mild to moderate, but can vary in severity.

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Signs and symptoms include:

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• Flat, light brown spots on the skin (cafe au lait spots).These harmless spots are common in many people. Having more than six Café-au-lait spots suggests neurofibromatosis 1 (NF1). They are usually present at birth or appear during the first years of life. After childhood, new spots stop appearing.

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• Freckling in the armpits or groin area.Freckling usually appears by ages 3 to 5. Freckles are smaller than Café-au-lait spots and tend to occur in clusters in skin folds.

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• Tiny bumps on the iris of the eye (Lisch nodules).These harmless nodules cannot easily be seen and do not affect vision. Lisch nodules of the iris are present in more than 90% of patients.

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• Soft, pea-sized bumps on or under the skin (neurofibromas).These benign tumors usually develop in or under the skin, but can also grow inside the body. Sometimes, a growth will involve many nerves (plexiform neurofibroma). Plexiform neurofibromas, when located on the face, can cause disfigurement. Neurofibromas may increase in number with age.

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• Bone deformities.Abnormal bone development and a deficiency in bone mineral density can cause bone deformities such as a curved spine (scoliosis) or a bowed lower leg.

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• Tumor on the optic nerve (optic glioma).These tumors usually appear by age 3, rarely in late childhood and adolescence, and almost never in adults.

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• Learning disabilities.Impaired thinking skills are common in children who have NF1 but are usually mild. Often there is a specific learning disability, such as a problem with reading or mathematics. Attention-deficit/hyperactivity disorder (ADHD) and speech delay also are common.

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• Larger than average head size.Children with NF1 tend to have a larger than average head size due to increased brain volume.

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• Short stature.Children who have NF1 often are below average in height.

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Bilateral acoustic neuromas are a hallmark feature of Neurofibromatosis type 2.

Hint

Anthrax is caused by Bacillus anthracis a Gram positive rod.

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Cutaneous anthrax is caused by direct contact of the bacteria into an open wound (usually touching an infected animal). Cutaneous anthrax is associated with a black eschar without pus, tends to be painless and to have widespread oedema.

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Without antibiotics, mortality is of the order of 20%, but with antibiotics, mortality is low, which contrasts with pulmonary anthrax.

Hint

This lady presents with an asymptomatic eruption on her trunk. The lesions are scaly, hypopigmented, and are not associated with any systemic disease. This is characteristic of pityriasis versicolor, which is caused by the unicellular yeast Pityrosporum ovale and Pityrosporum orbiculare. The yeast is lipophilic and is encouraged by an increase in environmental temperature, thus many patients notice that the condition begins after a summer vacation.

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It is a disorder of the healthy, but the immunocompromised are at risk.

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The condition is asymptomatic and appears pale in comparison to the normal skin. The fungus affects the melanocytes hence the hypo-pigmentation.

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The treatment options include topical imidazole creams, selenium sulphide shampoo and, if not responding to topical treatment, oral itraconazole 200 mg once a day for seven days.

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In this lady the topical treatment should be tried first

Hint

This gentleman has developed skin pigmentation and blue-grey discolouration of his legs as a side effect of treatment of his acne rosacea.

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Tetracyclines are commonly used treatment for acne rosacea. Long-term use of minocycline in particular has been associated with non-dose dependent blue-grey pigmentation of skin in the lower legs, and mucosal pigmentation. This is more common in the elderly. On biopsy, intracellular pigment is seen in the dermis and the subcutaneous tissue and stains positively for melanin and iron. If not extensive, hyperpigmentation may partially regress after minocycline is discontinued. If it persists, alexandrite laser therapy can be effective.

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Amiodarone can also cause a blue-grey slate discolouration of the skin, typically in sun exposed areas. You would therefore expect the face to be affected, and also amiodarone is not a treatment for acne rosacea which has been mentioned in this question to lead you to the correct answer.

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Hypersensitivity to the sun has been described with ciprofloxacin, but discolouration as in this scenario is not recognised.

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Oxytetracycline and doxycycline can lead to photosensitivity, but skin pigmentation seems to be specific to minocycline rather than a class effect of the tetracyclines

Hint

This is erythroderma which is a dermatological emergency.

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The gentleman needs admission with close supervision and supportive treatment with IV fluids and antibiotics.

Hint

The diagnosis of molluscum contagiosum is obvious when a child presents with pearly white hemispherical lesions particularly if they are umbilicated over limbs, trunk or face in various stages of evolution.

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Human immunodeficiency virus (HIV) positive patients may present with cryptococcosis. Cryptococcus neoformans infection affects 5-10% of patients with AIDS in the United Kingdom and USA and 30-40% in Africa. Up to 20% of patients with disseminated disease may have skin involvement.

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In HIV/AIDS cryptococcal skin involvement should be suspected when papulonodular necrotising skin lesions with central umbilication, like molluscum contagiosum are encountered in such patients along with pulmonary or neurological disease. Hence cutaneous cryptococcosis must be kept as a differential in a case of umbilicated lesions on the skin.

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Folliculitis presents with painful papulopustular follicular lesions.

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Herpes simplex infection presents with recurrent grouped vesicular eruptions on an erythematous base at mucocutaneous junctions.

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Warts present with verrucous plaques and papules more commonly over extremities.

Hint

Certain supplements are important in wound healing particularly zinc, vitamin C, and arginine.

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Zinc is a component of many of the enzymes responsible for wound healing.

Hint

Pemphigoid, erythema multiforme, and herpes are the commonest causes of a blistering rash.

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The history above is a classic description of bullous pemphigoid.

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Bullous pemphigoid is a blistering skin disease characterized by an autoimmune response to 2 hemidesmosomal proteins within the dermal-epidermal junction, designated BP180 and BP230. While BP230 localizes intracellularly and associates with the hemidesmosomal plaque, BP180 is a transmembrane glycoprotein with an extracellular domain. Most patients with bullous pemphigoid have autoantibodies binding to an immunodominant region of BP180, the noncollagenous 16A domain (NC16A), which is located extracellularly close to the transmembrane domain of the protein. Autoreactive T and B cell responses to BP180 have been found in patients with bullous pemphigoid. Passive transfer of antibodies to the murine BP180 ectodomain triggers a blistering skin disease in mice that closely mimics human bullous pemphigoid. Lesion formation in this animal model depends upon complement activation, mast cell degranulation and accumulation of neutrophils and eosinophils. Patients’ autoantibodies to BP180 induce dermal-epidermal separation in cryosections of human skin when co-incubated with leukocytes. The loss of cell-matrix adhesion is mediated by proteinases released by granulocytes. The increased knowledge of the pathophysiology of bullous pemphigoid should facilitate the development of novel therapeutic strategies for this disease.

Hint

It has been reported that venous ulcerations are the most common type of ulcer affecting the lower extremities. The probable underlying cause of venous congestion, which may promote ulceration, is venous insufficiency.

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The treatment of venous ulceration is control of oedema, treating any infection, and compression. However, compressive dressings or devices should not be applied if the arterial circulation is impaired.

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It is thus important to identify any arterial disease, and ankle-brachial pressure index is a simple way of doing this. One may then progress to lower limb arteriogram if indicated.

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There is no clinical sign of infection, and although a bacterial swab would help to rule out pathogens within the ulcer, arterial insufficiency is the more important issue.

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If there is a clinical suspicion of deep vein thrombosis (DVT) then duplex (or rarely a venogram) is indicated to decide on the indication for anticoagulation.

Hint

The answer is oral fluconazole. The presentation here is consistent with candida related intertrigo, as a result of this patient’s diabetes and obesity, which leads to skin folds being warm and moist, increasing the chances of fungal infection. The debate is between topical and oral therapy, but given this patient has very extensive infection and a history of diabetes (known to result in relative immunosuppression), oral intervention is preferred to the topical option. In total oral fluconazole can be given for a period of 2-4 weeks.

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Intensified glycaemic control will be useful in reducing the risk of future infection, but it is highly unlikely to eradicate the current problem, and as such anti-fungal intervention is preferred. Both topical clotrimoxazole and terbinafine are options in patients with more limited infection, and hydrocortisone may be added where there is marked inflammation but is not used as monotherapy.

Hint

This is a typical case of Stevens-Johnson syndrome.

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Stevens-Johnson syndrome (SJS) is an immune-complex-mediated hypersensitivity complex that is a severe expression of erythema multiforme.

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Stevens-Johnson syndrome (SJS) typically involves the skin and the mucous membranes. While minor presentations may occur, significant involvement of:

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• oral

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• nasal

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• eye

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• vaginal

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• urethral

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• gastrointestinal (GI), and

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• lower respiratory tract mucous membranes

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may develop in the course of the illness.

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Gastrointestinal and respiratory involvement may progress to necrosis.

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Stevens-Johnson syndrome (SJS) is a serious systemic disorder with the potential for severe morbidity and even death.

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The drugs most closely associated with causing Stevens-Johnson syndrome are:

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• antibacterials

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• sulfonamides

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• anticonvulsants (oxicam)

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• non-steroidal anti-inflammatory agents (piroxicam and tenoxicam)

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• chlormezanone, and 

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• allopurinol.

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Hint

Erythroderma is an emergency as patients are susceptible to profound dehydration, infection, and hypothermia.

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Methotrexate would be the only correct treatment for someone with erythrodermic psoriasis.

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Steroids could lead to unstable pustular psoriasis and would not generally work.

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Hydroxychloroquine has little effect on psoriasis.

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Topical coal tar and dithranol are good treatments for chronic plaque psoriasis, but are highly irritant and would make the erythroderma much more inflamed and deteriorate his condition.

Hint

Telogen effluvium is triggered by many factors, which include treatment of pathological conditions using retinoids, beta-blockers, calcium channel blockers, depression medicines and non-steroidal anti-inflammatory drugs (NSAIDs). In the above case, the gentleman received topical therapy for his psoriasis, which might include retinoids and hence this is a clue to the correct answer.

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Trichotillomania, also called hair-pulling disorder, is a mental disorder that involves recurrent, irresistible urges to pull out hair from the scalp, eyebrows or other areas of the affected person’s body, despite trying to stop. This option can thus be ignored right away as no such hint has been given in the question.

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Thiamine deficiency is more related to rapid weight loss and less related to hair loss.

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Alopecia areata is a disease that happens when the immune system attacks hair follicles and causes hair loss. Hair follicles are the structures in skin that form hair. While hair can be lost from any part of the body, alopecia areata usually affects the head and face. Hair typically falls out in small, round patches about the size of a quarter, but in some cases, hair loss is more extensive. Most people with the disease are healthy and have no other symptoms.

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Iron deficiency can cause excessive hair shedding, which is again called telogen effluvium.

Hint

This gentleman is likely to have asteatotic eczema which is a common problem and will improve just with plain emollients.

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Xerotic skin is commoner in the elderly population especially in the winter months due to the dry heat from central heating.

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All the other suggestions may be appropriate in a patient resistant to first line treatment but the first line is to try emollients.

Hint

The gentleman presents with tense blisters on his arms, trunk and legs. He is otherwise well and there is no mucosal involvement. This is typical of bullous pemphigoid.

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Dermatitis herpetiformis presents with itchy excoriated areas in the elbows knees and buttocks.

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Erythema multiforme presents with characteristic target lesions.

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Herpes simplex is vesicular and in generalised cases the patient is likely to be unwell.

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Pemphigus presents with superficial erosions and usually there is mucosal involvement.

Hint

Venous ulcers are secondary to venous stasis and chronic stretching of the walls of the superficial veins. These eventually become thinner and ulcerate.

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The mainstay of treatment of venous ulceration is compression bandaging, which aims to improve venous return and thereby reduce venous hypertension.

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The patient should always have their Doppler’s and ABPI (ankle brachial pressure index) prior to compression. The ankle brachial pressure index (ABPI) should be greater than 1 before compression bandaging is used (this excludes significant arterial disease). 

Hint

The rapid onset of renal failure, coupled with a rash and eosinophilia is highly suspicious of a diagnosis of interstitial nephritis as a result of exposure to non-steroidal anti-inflammatory drugs or amoxicillin.

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40-60% of cases of interstitial nephritis are due to drug hypersensitivity. Those most commonly involved include penicillins, cephalosporins, vancomycin, non-steroidal anti-inflammatory drugs (NSAIDs), thiazides and furosemide. Interstitial nephritis usually develops within 2-60 days of treatment with a beta-lactam, and presents with haematuria, acute kidney injury (AKI), and fever. A maculopapular rash and hepatic involvement can also occur. Interstitial nephritis associated with non-steroidal anti-inflammatory drugs (NSAIDs) is most commonly seen in elderly patients who have taken non-steroidal anti-inflammatory drugs (NSAIDs) intermittently for months to years. Proteinuria is dominant, and the nephrotic syndrome can develop.

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Ultrasound scanning is generally recommended in all cases of acute kidney injury, to exclude renal tract obstruction. In interstitial nephritis, renal size is usually normal and there may be some increased cortical echogenicity. A definite diagnosis can only be made with renal biopsy, which usually shows mononuclear cell infiltrate throughout the interstitium with associated oedema.

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The mainstay of treatment is to withdraw any drug which may be causative. High-dose prednisolone is indicated in some cases to hasten recovery. Dialysis may be required in acute cases.

Hint

The history of photosensitive eruption, hypertrichosis, and milia formation (keratin-containing cysts) are characteristic of porphyria cutanea tarda (PCT).

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Bullous pemphigoid is a rare skin condition that mainly affects older people. It usually starts with an itchy, raised rash. As the condition develops, large blisters can form on the skin. It may last a few years and sometimes causes serious problems, but treatment can help manage the condition in most cases.

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Acute intermittent porphyria usually causes intermittent neurological and abdominal problems.

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Subacute lupus erythematous (LE) can cause erythema and scarring, but in a patient with increased alcohol intake and hypertrichosis the most likely diagnosis is porphyria cutanea tarda (PCT).

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Erythropoietic protoporphyria patients get pain and erythema on exposure to sunlight.

Hint

In hypersensitive patients, aspirin can cause:

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• angioedema

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• bronchospasm, and

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• urticaria (skin rashes).

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Hint

The history of non-itchy, circular, raised, smooth-surfaced lesions on the elbows, extensor aspects of the forearms and knuckles and the raised borders are suggestive of granuloma annulare.

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Discoid eczema tends to be scaly and pruritic in nature.

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Psoriasis typically has a silvery scale and can be pruritic.

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Urticaria lasts for a few hours and is pruritic.

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Tinea corporis is a fungal infection and is typically scaly and pruritic in nature.

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The most likely answer is therefore granuloma annulare. This can be associated with diabetes.

Hint

Long term immunosuppression, for example with ciclosporin, can predispose patients with autoimmune disorders or transplant to infections and malignancy. The most common malignancies are squamous cell carcinoma (SCC) or basal cell carcinoma (BCC) of the skin. The description of this lesion most classically fits that of a squamous cell carcinoma (SCC). Basal cell carcinomas (BCCs) classically occur on the face or in sun-exposed areas, and are red/pink and pearly in nature. They may also ulcerate.

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Malignant melanoma is usually an irregular, pigmented, growing mole that may be asymmetrical and showing worrying features e.g. bleeding.

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Seborrhoeic keratoses are benign keratinised warts which are a sign of skin aging.

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Actinic keratosis is a dry pre-cancerous skin change associated with sun exposure. 

Hint

This gentleman has features of CREST syndrome, making systemic sclerosis the most likely diagnosis.

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Systemic sclerosis is a chronic autoimmune disease characterised by increased fibroblast activity and fibrosis in a number of different organ systems. Ninety to 95% of patients have positive antinuclear antibodies.

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There are two major subtypes:

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• limited cutaneous, and

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• diffuse cutaneous.

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CREST syndrome is an older term for the limited cutaneous form (calcinosis, Raynaud’s’ phenomenon, oesophageal dysmotility, sclerodactyly, telangiectasia).

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Patients with systemic sclerosis can present with the following:

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• skin abnormalities

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• musculoskeletal changes

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• gastrointestinal complications

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• pulmonary disease

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• renal crisis, and

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• dry eyes and mouth.

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A number of autoantibodies against extractable nuclear antigens can be detected in patients with systemic sclerosis. Anticentromere antibodies and anti topoisomerase I antibodies are the classic autoantibodies associated with the disease.

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Anticentromere antibodies are linked with limited cutaneous involvement and isolated pulmonary hypertension, and a good prognosis, whereas anti topoisomerase I is linked with diffuse skin disease and pulmonary fibrosis and a higher mortality.

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Additional autoantibodies which can be detected are anti-RNA polymerase, anti-U3RNP, antiKu, and ant-iU1RNP.

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Anticardiolipin antibodies are seen in antiphospholipid syndrome.

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Anti-DNA antibodies are associated with systemic lupus erythematosus (SLE).

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Antimitochondrial antibodies are seen in primary biliary cirrhosis.

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Antimyeloperoxidase antibodies are also referred to as p-anti-neutrophil cytoplasmic antibodies (pANCA), and can be seen in a variety of vasculitides.

Hint

Dermatophytosis is common in young adults. It usually presents with annular scaly plaques with active peripheral margins and central clearing resulting in increasing size of the lesions. The lesions are typically itchy and increase in number over a period of time. The affliction of legs and thighs is termed tinea corporis. It is an occupational dermatoses in athletes and may be recurrent in them if due precautions are not taken. The condition is contagious and can typically spread in immediate contacts, such as family members, if treatment is delayed or precautions are not taken.

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Allergic contact dermatitis will present with itchy papulovesicular eruption at the site of contact of the allergen.

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Fixed drug eruption presents with erythematous or hyperpigmented macules or patches, sometimes with central bullae. History of drug intake may be forthcoming and a history of other recurrent episodes at the same site may be present.

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Psoriasis presents with papulosquamous lesions with micaceous scaling. Annular lesions may be present. Itching is not a feature.

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Sarcoidosis may present with scaly plaques; however, features of peripheral activity and central clearing are usually not seen and itching is not a feature.

Hint

Pemphigus is associated with loss of intercellular cohesion in the lower part of the epidermis, leading to acantholysis (separation of keratinocytes). Pemphigus is classically associated with flaccid blistering, and often with immunoglobulin (Ig) G antibodies.

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Treatment may be successful with azathioprine.

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Pemphigoid is associated with subepidermal bullae

Hint

Given the history, the likely diagnosis is cutaneous leishmaniasis. Lesion pain and pruritus may be present in cutaneous leishmaniasis but is not typical.

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Diagnosis is by histological section with staining for amastigotes.

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Leishmania braziliensis is the likely pathogen which is spread by sandfly bites in endemic areas.

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Fusobacterium causes the tropical ulcer which is an intensely painful, shallow ulcer.

Hint

Hair dye contains substances which may induce an eczematous response in form of contact allergic dermatitis.

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This type of reaction is typical for this sort of time scale, and is an example of a type IV, or delayed, hypersensitivity reaction.

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Sensitisation occurs on initial exposure to the allergen and ‘memory’ T-cells proliferate in lymphoid tissue. Subsequent exposure to allergen induces activation of the T-lymphocytes and an inflammatory response.

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Hairdressing chemicals are a very common cause of contact allergic dermatitis, a disorder which is very common amongst the hairdressing community.

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A lady at this age is unlikely to present with a new, previously undiagnosed case of eczema.

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Acne rosacea is usually a disorder of the skin on the cheeks and nose.

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Acute cutaneous lupus erythematosus (CLE) presents with an erythematous rash over the face and neck. However, there are no eczematous features

Hint

This gentleman presents with pruritic vesicles on his elbows, knees, and buttocks which have not responded to topical steroids. This is the classical presentation of herpetiformis dermatitis.

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Atopic dermatitis (atopic eczema) usually is flexural and responds to topical steroids.

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Henoch-Schönlein purpura is a form of vasculitis.

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In scabies there are burrows and in psoriasis the rash consists of plaques with silvery scales.

Hint

Pityriasis versicolor (also called tinea versicolor) is a skin lesion caused by a fungus called Malassezia furfur.

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The treatment is topical selenium sulphide.

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Oral itraconazole is also effective.

Hint

Reassurance that this condition will resolve is the most appropriate action here. The most likely cause for erythema nodosum (EN) in this case is the tuberculosis itself. Given that she is committing to quadruple antibiotic therapy, you would expect the erythema nodosum (EN) to resolve as the infection subsides and therefore no specific treatment for the erythema nodosum (EN) is warranted.

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Topical diclofenac and antibiotics are not effective in this situation. The underlying panniculitis which is responsible for erythema nodosum (EN) is not infective in nature, and responds best, if required to topical potassium iodide. Oral corticosteroids may blunt her immune response to tuberculosis (TB) and should therefore be avoided. In summary, topical potassium iodide can be considered in patients with very troublesome erythema nodosum (EN), but other treatment is not indicated in this situation.

Hint

Cyclosporin is a well used drug in the treatment of atopic dermatitis (AD). It is usually at doses of 2-5 mg/kg.

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The pathophysiology of atopic dermatitis (AD) is complex but the T-lymphocytes are involved and it is known that there is an increased production of cytokines particularly IL-4.

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Cyclosporin is a suppressor of T-cells and in that respect works very well in atopic dermatitis and psoriasis. The side effects of hypertension and renal toxicity limit its use.

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These patients are seen monthly to have their blood pressure and serum urea and serum electrolytes checked.

Hint

Discoid lupus is photosensitive and so avoiding the sun with protective clothing and sunscreens, and changing behaviour is important.

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Topical or intradermal steroids and hydroxychloroquine are useful therapies to prevent scarring and new lesions appearing. The latter are less effective if patients continue to smoke.

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If these treatments are ineffective, second line drugs such as methotrexate, azathioprine, or thalidomide may be used.

Hint

The description is that of acne rosacea particularly in view of the distribution, duration and absence of any other features.

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The most appropriate treatment is a tetracycline.

Hint

The distribution of the lesions suggests a photosensitive element.

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Both lupus erythematosus and porphyria cutanea tarda (PCT) are associated with a photosensitive element; however, this is more typical of porphyria cutanea tarda (PCT).

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Porphyria cutanea tarda (PCT) causes blistering of the hands and the forehead which usually heal with small scar and milia formation.

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It is also associated with an excessive alcohol intake.

Hint

Potential causes of erythema multiforme include:

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Infections:

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• Viruses – herpes simplex 1 and 2, hepatitis B, Epstein-Barr virus (EBV), enteroviruses

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• Small agents – Mycoplasma pneumoniae

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• Bacteria – Group A Streptococcus, eosin, and

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• Other – Mycobacterium tuberculosis, histoplasma, coccidioides.

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Neoplasia:

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• Leukaemia, and

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• Lymphoma.

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Antibiotics:

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• Penicillins

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• Sulphonamides

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• Isoniazid, and

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• Tetracycline.

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Anticonvulsants:

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• Phenytoin

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• Phenobarbitone, and

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• Carbamazepine.

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Other caused include:

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• Aspirin

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• Radiation therapy

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• Etoposide

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• Non-steroidal anti-inflammatory drugs (NSAIDs)

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• Sunlight, and

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• Pregnancy.

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Hint

The mnemonic of ABCDE regarding characteristics of a melanoma are as follows:

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• A – Asymmetry – one half of the lesion does not match the other half

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• B – Border irregularity

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• C – Colour variegation – pigmentation is not uniform

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• D – Diameter – a diameter 7 mm warrants investigation although changes in size are also important

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• E – Evolution – evolving size or changes in characteristics such as nodules.

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Hint

Survival is strongly correlated with depth of melanoma at the point of diagnosis, with lesions over 4.0 mm thick being associated with a particularly poor outcome.

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Other predictors of a poor outcome include increasing age and male sex.

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Ulceration of the lesion also implies greater risk of metastases. For lesions over 4.0 mm thick with ulceration, five year survival is less than 50%.

Hint

This lady has seborrhoeic dermatitis which tends to affect the hair bearing areas of skin with the scalp the worst affected.

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It is thought that, at least in part, the activity of activated T-cells may be enhanced by an increased reservoir of Malassezia yeasts. As such, regular washing of the hair with a ketoconazole based shampoo has been shown to reduce the severity of the condition.

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Topical corticosteroids have been shown to hasten recovery, but may be associated with a rebound effect and rapid recurrence of the rash when they are withdrawn.

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Coal tar shampoo and topical tacrolimus are alternate treatments.

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Asteatotic dermatitis typically presents in the elderly with pruritic, xerotic, scaly skin typically over the shins but may occur over the back and hands. Tar based preparations are never used as they would worsen the condition.

Hint

This gentleman presents with tender lesions three weeks after a sore throat.

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This is most likely to be post-streptococcal erythema nodosum and antistreptolysin-O titre (ASOT) is most likely to confirm this.

Hint

Many drugs have been implicated in the development of erythema multiforme, and the Stevens-Johnson syndrome subtype.

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Most commonly associated is allopurinol.

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Also associated are:

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• recent drugs – nevirapine, lamotrigine, sertraline, pantoprazole, tramadol

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• antibiotics – sulphonamides, co-trimoxazole, penicillin, cephalosporins, fluoroquinolones, vancomycin

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• NSAIDs – piroxicam, fenbufen, ibuprofen, ketoprofen, naproxen, tenoxicam, diclofenac, sulindac

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• anti-TB – rifampicin, ethambutol, isoniazid, pyrazinamide

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• anticonvulsants – barbiturates, carbamazepine, phenytoin, valproate, lamotrigine

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• antifungals – fluconazole, nystatin, griseofulvin, and

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• antidepressants – lamotrigine, sertraline.

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Of the options given, sulphasalazine is the most commonly associated.

Hint

The correct answer is IgG deposition at the dermal-epidermal junction. The clinical presentation here is consistent with bullous pemphigoid, which occurs as a result of IgG antibodies which bind to the skin basement membrane. This accounts for the findings on biopsy. Oral lesions are less typically seen in pemphigoid compared to pemphigus where they are much more common.

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Granuloma formation with neutrophilic infiltrates is seen in patients with erythema nodosum, which has a number of associations but the lesions are more characteristically present only on the shins and do not blister.

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Intercellular deposition of IgG is seen in pemphigus vulgaris, where oral lesions are much more prominent. Neutrophils in the dermal papillae are a feature of dermatitis herpetiformis, which is a pruritic skin rash classically located on the elbows and associated with coeliac disease. T-cell infiltration is seen in Stevens Johnson syndrome, which is a rapidly progressive condition characterised by flu-like symptoms followed by an extensive erythematous rash (including the mucosal surfaces) which subsequently blisters.