Introduction: Insulin-induced local amyloidosis (ILA) was firstly described in 1983, but still underdiagnosed. Here we describe clinicopathological and electron microscopic findings of a case with ILA. Case: A 52-year-old male with type 2 diabetes mellitus for 14 years, on basal-bolus insulin (i.e., insulin lispro and glargine), had noticed 2x2 cm mass at injection site. MRI showed a fibrous mass at the subcutaneous tissue. Punch biopsy of the lesion revealed amyloid deposition surrounded by giant cells. Immunohistochemistry studies proved that amyloid material is insulin. Electron microscopic evaluation (EM) revealed both extra-, and intracellular amyloid fibrils (Figure 1A,B). Discussion: Local amyloid deposition due to insulin injection could be seen in both types of diabetes. Despite earlier reports were associated with porcine insulin, subsequent publications linked also with human insulin and recombinant insulin analogues. High doses of insulin and inappropriate insulin injections are the major risk factors. Extracellular amyloid deposits in ILA arises primarily from exogenous insulin, but the precise mechanism of pathogenicity remains to be established. There are only few case reports of ILA with EM. To the best of our knowledge, here in this case we have firstly showed intracellular accumulation of those amyloid fibrils as well as extracellular compartment, which might have further clinical implications.
S. Sendur: None. K. Katipoglu: None. O. Kockara: None. Ö. Gököz: None. F. Kaymaz: None. S. Dagdelen: None.