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Chapter 054. Skin Manifestations of Internal Disease (Part 15)

Several metabolic disorders are associated with blister formation, including diabetes mellitus, renal failure, and porphyria. Local hypoxia secondary to decreased cutaneous blood flow can also produce blisters, which explains the presence of bullae over pressure points in comatose patients (coma bullae). In diabetes mellitus, tense bullae with clear viscous fluid arise on normal skin. The lesions can be as large as 6 cm in diameter and are located on the distal extremities. There are several types of porphyria, but the most common form with cutaneous findings is PCT. In sun-exposed areas (primarily the face and hands), the skin is. | Chapter 054. Skin Manifestations of Internal Disease Part 15 Several metabolic disorders are associated with blister formation including diabetes mellitus renal failure and porphyria. Local hypoxia secondary to decreased cutaneous blood flow can also produce blisters which explains the presence of bullae over pressure points in comatose patients coma bullae . In diabetes mellitus tense bullae with clear viscous fluid arise on normal skin. The lesions can be as large as 6 cm in diameter and are located on the distal extremities. There are several types of porphyria but the most common form with cutaneous findings is PCT. In sun-exposed areas primarily the face and hands the skin is very fragile and trauma leads to erosions and tense vesicles. These lesions then heal with scarring and formation of milia the latter are firm 1- to 2mm white or yellow papules that represent epidermoid inclusion cysts. Associated findings can include hypertrichosis of the lateral malar region men or face women and in sun-exposed areas hyperpigmentation and firm sclerotic plaques. An elevated level of urinary uroporphyrins confirms the diagnosis and is due to a decrease in uroporphyrinogen decarboxylase activity. Precipitating agents include alcohol iron chlorinated hydrocarbons hepatitis C infection and hepatomas. The differential diagnosis of PCT includes 1 porphyria variegata the skin signs of PCT plus the systemic findings of acute intermittent porphyria it has a diagnostic plasma porphyrin fluorescence emission at 626 nm 2 drug-induced pseudoporphyria the clinical and histologic findings are similar to PCT but porphyrins are normal etiologic agents include naproxen furosemide tetracycline and nalidixic acid 3 bullous dermatosis of hemodialysis the same appearance as PCT but porphyrins are usually normal or occasionally borderline elevated patients have chronic renal failure and are on hemodialysis 4 PCT associated with hepatomas hepatic carcinomas and hemodialysis and 5 epidermolysis