57-year-old man • type 2 diabetes • neuropathy • bilateral foot blisters • Dx?

THE CASE

A 57-year-old man with type 2 diabetes, hyperlipidemia, and obesity presented to the emergency department (ED) for bilateral foot blisters, both of which appeared 1 day prior to evaluation. The patient’s history also included right-side Charcot foot diagnosed 4 years earlier and right foot osteomyelitis diagnosed 2 years prior. He had ongoing neuropathy in both feet but denied any significant pain.

The patient wore orthotics daily and he’d had new orthotics made 6 months prior; however, a recent COVID-19 diagnosis and prolonged hospital stay resulted in a 30-pound weight loss and decreased swelling in his ankles. He acquired new shoes 2 weeks prior to ED presentation.

Physical examination revealed large blisters along the medial aspect of the patient’s feet, with both hemorrhagic and serous fluid-filled bullae. The lesions were flaccid but intact, without drainage or surrounding erythema, warmth, or tenderness. The blister on the left foot measured 8 x 5 cm and extended from the great toe to mid-arch (FIGURE), while the one on the right foot measured 8 x 3 cm and extended from the great toe to the base of the proximal arch. Sensation was decreased in the bilateral first and second digits but unchanged from prior documented exams. Bilateral dorsalis pedis pulses were normal.

Work-up included imaging and lab work. The patient’s complete blood count was normal, as were his erythrocyte sedimentation rate and C-reactive protein level. Radiographs of the right foot were normal, but those of the left foot were concerning, although inconclusive, for osteomyelitis. Further evaluation with magnetic resonance imaging of his left foot revealed a deformity of the first digit with some subchondral signal change that was thought to be posttraumatic or degenerative, but unlikely osteomyelitis.

THE DIAGNOSIS

Podiatry was consulted for blister management. Based on atraumatic history, rapid appearance, location of blisters, unremarkable lab work and imaging, and concurrent diabetes, the patient received a diagnosis of bilateral bullous diabeticorum (BD).

DISCUSSION

Roughly one-third of patients with diabetes will experience some cutaneous adverse effect because of the disease.¹ Common iterations include acanthosis nigricans, rash, or even infection.² BD is a rare bullous skin lesion that occurs in patients with diabetes; it has a reported annual incidence of 0.16% and may be underdiagnosed.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 bullous diabeticorum occurrence.

Cases of BD have been described both in patients with longstanding diabetes and in those newly diagnosed, although the former group is more often affected.¹ BD is reported more frequently in males than females, at a ratio of 2:1.^1,3 Patients ages 17 to 80 years (average age, 55 years) have received a diagnosis of BD.¹ Most affected patients will have a concomitant peripheral neuropathy and sometimes nephropathy or retinopathy.¹

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