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Systemic dermatology

Cutaneous medicine key points test

Endocrine disease # More than 90% of those with necrobiosis lipoidica have Type 1 diabetes #! Diffuse hair loss may be due to hyper- or hypo-thyroidism # Pretibial myxoedema suggests hypothyroidism #! Cushing’s syndrome can result in acne, hirsutism and cutaneous atrophy Explanation: About 50-80% of patients presenting with necrobiosis lipoidica have diabetes mellitus, most often Type 1. Hypothyroidism may present with diffuse hair loss, dry skin and itching. Hyperthyroidism may also cause hair loss and itching, and pretibial myxoedema suggests Grave's disease. Cushing's syndrome can result in acne, hirsutism, striae and cutaneous atrophy. Gastrointestinal disease # Dermatitis herpetiformis can be found in nearly all patients presenting with gluten sensitive enteropathy # Malabsorption of copper results in acrodermatitis enteropathica #! Inflammatory bowel disease is associated with pyoderma gangrenosum #! Polyposis coli is associated with familial epidermal cysts Explanation: About 80% of those with dermatitis herpetiformis (DH) have evidence for at least histological gluten sensitive enteropathy (GSE), but very few of those presenting with symptomatic GSE have DH. Renal disease # Acute renal failure may cause generalised pruritus #! Chronic renal failure may cause calciphylaxis # Chronic renal failure is associated with neutrophilic dermatoses #! Renal transplantation patients have a high risk of squamous cell carcinoma Explanation: Chronic renal failure (and not acute renal failure) is associated with pruritus, calcinosis, calciphylaxis, perforating collagenosis and porphyria cutanea tarda. Renal transplantation gives rise to a high risk of warts and skin cancers (especially squamous cell carcinomas) because of long term immunosuppressive medication. Haematological disease #! Cryoglobulinaemia may cause purpura on cold-exposed areas #! Generalised pruritus can be due to iron deficiency anaemia # Idiopathic thrombocytopaenia is associated with pyoderma gangrenosum # Leukaemia may result in blistering on sun exposed sites Explanation: Purpura associated with haematological disease may be due to thrombocytopaenia, disseminated intravascular coagulation or cryoglobulinaemia. Generalised pruritus can be due to iron deficiency anaemia or polycythaemia vera. Pyoderma gangrenosum and Sweet's disease are sometimes associated with leukaemia. Leukaemic infiltrates may present as erythematous, purpuric or ulcerated cutaneous nodules. Porphyria #! Excessive porphyrins in blood, urine or faeces are diagnostic # Porphyria cutanea tarda presents in childhood with pain and blistering on sun exposure # Erythropoeitic porphyria presents with skin fragility and sub-epidermal bullae #! Porphyria cutanea tarda is associated with haemochromatosis Explanation: Diagnosis of porphyria is confirmed by detection of excessive porphyrins in blood, urine or faeces. EPP presents in childhood with pain and blistering on minimal sun exposure. PCT and VP present with skin fragility, sub-epidermal bullae and hypertrichosis. PCT is associated with liver disease, hepatitis C infection, haemochromatosis, and excess alcohol or oestrogen ingestion. Hyperlipidaemias * Xanthelasmata are due to hypertriglyceridaemia *! Cutaneous xanthomata are nearly always associated with hyperlipidaemia Explanation: Cutaneous eruptive, tuberous, plane or tendinous xanthomata are nearly always associated with specific patterns of primary or secondary hyperlipidaemia. Xanthelasmata may or may not be associated with hypercholesterolaemia. Sarcoidosis * Cutaneous sarcoidosis often results in blistering on sun-exposed sites * Sarcoidosis is diagnosed by the presence of caseating granulomas * Lupus pernio is associated with bihilar lymphadenopathy and mild pulmonary disease *! Systemic steroids may be very effective Explanation: Cutaneous sarcoidosis results in papules, nodules, plaques and ulcers. It is diagnosed histologically by the presence of noncaseating granulomas in affected organs. Lupus pernio (bluish nose, cheeks, ears and fingers) is associated with severe pulmonary disease. The mainstay of treatment of severe disease is systemic steroids. Oral ulceration, genital ulceration and iritis are characteristic of: * Scurvy * Sarcoidosis *! Behçet’s disease * Amyloidosis Explanation: Behçet’s disease presents with the combination of oral and genital ulceration and iritis. Other systemic symptoms are common. Corkscrew hairs and bleeding gums are typical of: * Pellagra *! Scurvy * Kwashiorkor * Fatty acid deficiency Explanation: Vitamin C deficiency (scurvy) presents with corkscrew hairs and bleeding gums or easy bruising. Nicotinic acid deficiency (pellagra) presents with photosensitive eruption on neck and feet, diarrhoea and dementia. Protein deficiency (kwashiorkor) may cause dry red skin and hair and is associated with oedema and ascites. Fatty acid deficiency may result in dry red skin and delayed healing. Obesity gives rise to an increased risk of: # Amyloidosis #! Bromhidrosis # Mycetoma #! Intertrigo Explanation: Obesity is associated with a higher incidence of intertrigo, skin tags, acanthosis nigricans, striae, hyperhidrosis and bromhidrosis.