Toxicity of insulin-derived amyloidosis: a case report

Insulin-derived amyloidosisis a skin-related complication of insulin therapy that interferes with insulin therapy. Although toxicitiesof in vitro-formed insulin amyloidfibrils have been well studied, the toxicityof insulin-derived amyloidosisremains to be clarified. A 58-year-old man with type 2 diabetes mellitus underwent a lower limb amputationdue to diabetic gangrene. Several antibiotics including minocyclinewere administered for infection and sepsis. A hard mass at the insulin injection sites in the lower abdomen was discovered by chance four months later. Although no abnormal findings in the surface skin of the mass were observed, necrotic tissue was seen around the mass when a biopsy was performed. Histological and toxicitystudies were performed for this patient and four other patients with abdominal massesat insulin injection sites. Histological and immunohistochemical studies showed that the masses had typical characteristics of amyloiddeposits in all cases, whereas necrotic findings were seen adjacent to the amyloiddeposit only in the case presented. Toxicitystudies indicated that the amyloidtissue from the present case had significant cell toxicitycompared to the control skin tissue or the amyloidtissues from the other four cases. This report showed that toxicinsulin-derived amyloidosiscan occur. In addition, this report suggested that toxicinsulin-derived amyloidosismay cause necrosis in the surrounding tissue. Although the toxic amyloiddeposit of insulin-derived amyloidosiswas found in only one patient, no structural differences between toxicand non- toxicdeposits were seen on histological and immunohistochemical studies.