A 74-year-old woman presented to her primary care doctor for evaluation of two painless blisters on her right shin. Her medical history was significant for hypertension, hyperlipidemia, and type 2 diabetes with microalbuminuria. Her diabetes had been managed for more than 20 years and was currently controlled with oral medications (pioglitazone, sitagliptin, and metformin) and long-acting insulin.
She reported that the blisters spontaneously occurred on the preceding day with no history of trauma. She denied pain, pruritus, constitutional symptoms, and prior history of bullae. On exam, 2 tense 3 cm clear fluid-filled and 2 smaller bullae were present on her anterior right shin (Figure 1). Two 4 mm punch biopsies of the bulla were nondiagnostic and revealed eosinophilic infiltrate with intraepidermal spongiosis.
Figure 1. Two tense bullae on patient’s anterior right shin.
Without treatment, her bullae spontaneously drained clear fluid “like water” and resolved over the subsequent weeks. Exam at her 2-week follow up appointment revealed well circumscribed hyperpigmented patches (Figure 2). She was diagnosed clinically with bullosis diabeticorum.
Bullosis diabeticorum, or diabetic bullae, is a poorly understood but benign cutaneous manifestation of diabetes. This diagnosis in an older woman with longstanding diabetes highlights the importance of recognizing this condition to limit unnecessary alarm and unwarranted diagnostic tests.
Bullosis diabeticorum was first reported in 1930, although the term wasn’t coined until 1967.1 The condition is rare and occurs in approximately 0.5% of diabetics.2 Affected patients tend to have long-standing diabetes and other diabetic complications (including nephropathy like our patient and peripheral neuropathy).3 Bullae erupt abruptly and without trauma. They tend to occur on the feet and lower legs; however, they may also appear on fingers, hands, and arms. Fluid from the bullae is clear, sterile, and typically contains eosinophils.3 The etiology of this condition is unknown and the level of glycemic control does not appear to correlate with the occurrence of disease.
Figure 2. Two healed bullae, now hyperpigmented patches without inflammatory changes.
Diagnosis is one of exclusion and is based on presentation and clinical course. Histologic characteristics are nonspecific and reveal intraepidermal or subdermal separation.3 Direct immunofluorescence is often negative.3 While histology and immunofluorescence are usually nondiagnostic, they rule out autoimmune disorders such as bullous pemphigoid and epidermolysis bullosa acquista.
Bullosis diabeticorum is self-limited and the bullae typically resolve within 2 to 6 weeks without scarring. Some authors recommend needle aspiration of the bullae to prevent spontaneous rupture.4 The blister skin is then kept as a sterile dressing. Although necrosis and secondary infections are rare, clinicians should monitor the bullae closely until fully healed. Unroofed blisters may need to be followed by wound care specialists.5 Remind patients that bullae may reoccur. ■
1.Cantwell AR Jr, Martz W. Idiopathic bullae in diabetics. Bullosis diabeticorum. Arch Dermatol. 1967;96:42-44.
2.Poh-Fitzpatrick MB, Junkins-Hopkins JM. Bullous disease of diabetes. Availabe at: http://emedicine.medscape.com/article/1062235-overview. Accessed March 12, 2013.
3.Basarab T, Munn SE, McGrath J, Russell Jones R. Bullosis diabeticorum. A case report and literature review. Clin Exp Dermatol. 1995;20:218-220.
4.Lipsky BA, Baker PD, Ahroni JH. Diabetic bullae: 12 cases of a purportedly rare cutaneous disorder. Int J Dermatol. 2000;39:196-200.
5.Larsen K, Jensen T, Karlsmark T, Holstein PE. Incidence of bullosis diabeticorum--a controversial cause of chronic foot ulceration. Int Wound J. 2008;5(4):591-596.