Track

Case Reports

Abstract

Three-year-old boy with type 1 diabetes mellitus presented with three-month history of erythematous nodules at insulin pump injection sites. Ten months after initiating insulin pump therapy, he began to develop nodules at the injection sites, including all extremities, lower back, and buttocks. The nodules were mobile, tender, and indurated with erythema and ulceration and would occasionally drain purulent material. Fungal and bacterial cultures were negative, and patch testing showed mild nickel and aluminum allergy. The nodules did not respond to antimicrobial therapy but mildly improved with betamethasone. Punch biopsy of a lower back nodule demonstrated mid to deep dermal predominantly perieccrine, lymphocytic and neutrophilic inflammation that became more pronounced towards the deep dermis. Microorganism stains and cultures were negative. Despite switching to manual insulin injection, the patient formed new injection site nodules over the next two months. Excisional biopsy of a left upper extremity nodule showed deep dermal and pannicular abscess and granulomatous inflammation with neutrophils, lymphocytes, plasma cells, and eosinophils. Microorganism workup continued to be negative.  Given these findings, these features were consistent with a recently described pyoderma gangrenosum (PG)-like reaction to insulin pump therapy. Although various cutaneous reactions to insulin injections are known, including granulomatous and allergic responses, insulin pump-related reactions are an emerging area of interest. Theories behind the PG-like pathology include cascading neutrophilic responses to zinc complexes in insulin preparations and neutrophil activity modulation by insulin itself. This is only the second reported case of a PG-like inflammatory response to insulin in a modern device setting.