A 65-year-old male with diabetes and peripheral neuropathy (last glycosylated hemoglobin level 9.4 %) reported spontaneous development of a 14 × 9 cm, tense bulla on the medial aspect of his right lower extremity (Fig. 1). The lesion was non-inflammatory in appearance with a non-erythematous base and clear serous content. Nikolsky’s sign was negative. There were no other bullous skin lesions. The patient had no prior history of dermatologic disorders and denied any recent trauma, acute edema, or change in medications. The massive bulla spontaneously ruptured and healed without complication. The distribution and appearance of the bulla led to a clinical diagnosis of bullosis diabeticorum, a rare but likely underdiagnosed condition in patients with diabetes. Lesions appear rapidly, primarily in an acral distribution in areas of otherwise normal-appearing skin, and range from a few centimeters to very large. The differential diagnosis includes friction bullae, bullae due to burns or edema, bullous fixed drug reaction, bullous pemphigoid, and epidermolysis bullosa acquisita. Bullae resolve spontaneously but can recur, and secondary infection after rupture is a concern. The etiology of bullae formation in diabetics is unknown, although theories include microangiopathy1 and an enhanced vulnerability to trauma.2

Figure 1.
figure 1

Large, tense bulla on the lower extremity.

Full size image