A 58-year-old man presented to the hospital with chronic bullous ulcerative disease of his fingers complicated further by osteomyelitis (image A). His medical history included pancreatic cancer and type 2 diabetes mellitus complicated by retinopathy, neuropathy, and end-stage renal disease. Hemoglobin A_1c had ranged from 7.4% to 14.1% since the lesions first appeared. Recurrent tense, bullous lesions occurred only in his fingers and resolved spontaneously or progressed to osteomyelitis requiring amputation (image B) over the past 7 years. Results of the initial biopsy of the lesions showed intraepidermal vesiculobullous dermatitis with superficial epidermal necrosis. A second biopsy specimen showed spongiosis and sparse chronic inflammation without immunoreactivity. Without history of trauma, chemical injury, or underlying constitutional illness, and in the setting of nonspecific histopathologic findings and immunofluorescence findings that excluded noninflammatory bullous pemphigoid, porphyria cutanea tarda, and other bullous porphyrias, his presentation was consistent with bullous diabeticorum. Other bullous lesions, such as epidermolysis bullosum, were excluded. 

Bullous diabeticorum is a rare cutaneous, spontaneous, blistering condition affecting approximately 0.16% of patients with diabetes.¹ It is a diagnosis of exclusion with nonspecific histopathologic findings.² The pathophysiologic process remains unclear, though poor glycemic control is thought to play a role.¹