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Case Reports

Abstract

Amyloidosis, localized or systemic, describes the extracellular deposition of insoluble protein fibrils into tissues and organs. Few cases of localized insulin-derived amyloidosis, also referred to as amyloidoma or insulin ball, have been reported at subcutaneous injection sites, sometimes associated with poor glycemic control. One theory suggests exogenous insulin becomes misfolded causing insoluble fibril formation. We present a 63-year-old woman who developed an amyloidoma after years of repeated insulin injections in the left lower abdomen. On exam, there was an 18 x 11 cm ulcerated exophytic lesion. The patient reported injecting in the same location to minimize the risk of developing hyperpigmentation in multiple areas on the skin. The lesion was overall asymptomatic however spontaneously ruptured, prompting presentation to the hospital. Punch biopsy demonstrated histologic changes consistent with an insulin derived amyloidoma including deposits of dull, pink globular material throughout dermis. The Congo red stain was positive, showing green birefringence with polarization. Although there is a growing body of literature on amyloidomas, we have not previously seen reports of spontaneous rupture and ulceration in an insulin derived amyloidoma. While the cause of the rupture is not immediately understood, this case adds to the limited literature regarding amyloidomas and further highlights the importance of continued diabetic education including proper injection techniques, investigation of increases in insulin requirements, and comprehensive skin exams periodically at routine visits.