Zinc-induced granuloma--a unique complication of insulin therapy

A 55-year-old diabetic female treated with a combination of a short- and intermediate-acting insulin, developed sterile furunculoid lesions at the injection sites which eventually healed with atrophic scars. Histopathologically, an initial neutrophilic stage was followed by granulomatous and fibrotic stages. It was considered that zinc, a component of the intermediate-acting insulin, was responsible for the cutaneous reaction and granuloma formation. Zinc-induced granuloma is a rare histopathological complication of insulin therapy.