Other causes of subepidermal blisters
The bullae and erosions occur on the backs of the hands and on other areas exposed to sunlight.
A few diabetics develop unexplained blisters on their legs or feet. The backs of the hands of patients with chronic renal failure may show changes rather like those of porphyria cutanea tarda (pseudoporphyria). Frusemide (furosemide) can contribute to blister formation.
Vesicles and bullae may be seen in severe active sys-temic lupus erythematosus. This disorder is uncommon and carries a high risk of kidney disease. Non-cutaneous manifestations of systemic lupus ery-thematosus do not respond to dapsone; however, the bullae do.