Diagnosis: Bullosis diabeticorum
Direct immunofluorescence was negative. This, along with the patient’s history of diabetes, led us to diagnose bullosis diabeticorum in this patient. This condition, also known as bullous disease of diabetes, is characterized by abrupt development of noninflammatory bullae on acral areas in patients with diabetes. The skin appears normal except for the bullae.1 Bullosis diabeticorum occurs in just .5% of patients with diabetes.2 It is twice as common in men as in women.2
The etiology of bullosis diabeticorum is unknown. The acral location suggests that trauma may be a contributing factor. Although electron microscopy has suggested an abnormality in anchoring fibrils, this cellular change does not fully explain the development of multiple blisters at varying sites. Glycemic control is not thought to play a role.2
A large differential
The distribution of lesions and the presence—or absence—of systemic symptoms go a long way toward narrowing the differential of blistering diseases. The presence of generalized blistering and systemic symptoms would suggest conditions related to medication exposure, such as Stevens-Johnson syndrome or toxic epidermal necrolysis; infectious etiologies (eg, staphylococcal scalded skin syndrome); autoimmune causes; or underlying malignancy.3 Generalized blistering in the absence of systemic symptoms would support diagnoses such as bullous impetigo and pemphigoid.3
Lesion distribution provides important clues, too. Sun exposure-related causes typically leave lesions on the hands and forearms, not just the toes. A dermatomal distribution would suggest herpes zoster. A linear distribution of blisters argues for contact dermatitis. Mucous membrane involvement would suggest etiologies such as herpes simplex virus, erythema multiforme, pemphigus vulgaris, Stevens-Johnson syndrome, or toxic epidermal necrolysis.
Some conditions cannot be excluded from the differential diagnosis upon presentation. Hereditary epidermolysis bullosa (EB) represents a set of inherited diseases in which trauma causes blisters. Localized EB simplex, Weber-Cockayne subtype, can present in adulthood. Blisters can result from trauma on the hands or feet after excessive exercise.4 Although our patient did not give a history of excessive exercise, and this condition is rare, it and similar conditions must be ruled out.