Cutaneous insulin-derived amyloidosis presenting as hyperkeratotic nodules

Amyloidosis consists of approximately 30 protein-folding disorders in which a specific soluble precursor protein aggregates to form the insoluble fibrils of amyloid. Insulin is the hypothesized precursor protein in localized cutaneous insulin-derived (AIns) amyloidosis. Amyloid deposition at insulin injection sites can interfere with absorption, leading to poor glucose control. Despite the increasing prevalence of diabetes mellitus and insulin use, there is a paucity of published cases of AIns amyloidosis and a lack of awareness of this condition among both dermatologists and general practitioners. We report 2 patients with insulin-dependent diabetes who developed hyperkeratotic nodules at insulin injection sites. Our cases complement the current data on iatrogenic amyloidosis and provide insight into this likely underreported phenomenon.