The etiology of BD is unclear but appears to be multifactorial. Hypotheses suggest that there’s a link to neuropathy/nephropathy, excessive exposure to ultraviolet light, or a vascular cause secondary to hyaline deposition in the capillary walls.4,5
What you’ll see at presentation
The typical manifestation of BD is the rapid appearance of tense blisters, which may occur overnight or even within hours.1 They are usually painless; common locations include the feet, distal legs, hands, and forearms.1,5 The bullae can be serous or hemorrhagic.1
Most notable in the patient’s history will be a lack of trauma or injury to the area.1 Although A1C values do not correlate with blister formation, patients with hypoglycemic episodes and highly varying blood glucose values seem to have higher rates of occurrence.1
Other sources of blistering must be ruled out
The diagnosis of BD is clinical and based on history, exam, and exclusion of other bullous diagnoses.6 A key clue in the history is the spontaneous and rapid onset without associated trauma in a patient with diabetes.6 Direct immunofluorescence, although nonspecific, can be helpful to rule out other disorders (such as porphyria cutanea tarda and bullous pemphigoid) if the history and exam are inconclusive. Direct and indirect immunofluorescence is typically negative in BD.4,6
The differential diagnosis includes other conditions that involve bullae—such as frictional bullae, bullous pemphigoid, and bullous systemic lupus erythematosus—as well as porphyria, erythema multiforme, insect bites, or even fixed drug eruption.2,7
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