ANSWER 39
This patient has pemphigus vulgaris. This is a blistering disease where the level of the
blister is within the epidermis. The superficial nature of the blister means that the blisters
are prone to burst leaving a glistening red base which bleeds easily. The epidermis at the
edge of the blister is easily dislodged by sliding pressure (Nikolsky sign). Erosions in the
mouth are also common. Associated diseases include carcinoma, lymphoma, thymoma,
systemic lupus erythematosus and certain drugs such as penicillamine and captopril.
This elderly man also has hepatomegaly. With the rectal bleeding and microcytic anaemia,
it is likely that he has a left-sided colonic neoplasm. The raised alkaline phosphatase sug-
gests secondary metastases in his liver. He needs an ultrasound to image his liver and a
colonoscopy to visualize his colon. He should be referred to a surgeon to assess if pallia-
tive surgery is appropriate.
Pemphigus is itself life-threatening either due to insensible fluid losses or septicaemia as
a result of infection of the exposed blisters. The sore mouth and eroded skin need careful
nursing. Treatment is with high doses of corticosteroids, and cytotoxic drugs may need to
be added.
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- Pemphigoid: the level of bullae is deeper (subepidermal) and the blisters are larger
and rupture less often than in pemphigus. - Erythema multiforme: there are target-shaped lesions with central blisters, often
with generalized erythema and mucosal ulceration (Stevens–Johnson syndrome).
This is often associated with herpes simplex virus infection, certain drugs, e.g.
sulphonamides and neoplasms. - Dermatitis herpetiformis: there are vesicular lesions over the elbows, knees and
face. Vesicles are smaller than blisters (!0.5 cm) and often ruptured by itching. This
rash is associated with coeliac disease. - Miscellaneous blistering disorders: diabetes mellitus, herpes gestationis and
familial blistering disorders.
Main differential diagnoses of blistering diseases- Pemphigus is often associated with underlying serious medical conditions.
- Pemphigus may be fatal usually due to septicaemia as a result of super-added infection
of blisters and immunosuppressive treatment.