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Insulin-derived amyloidosis is a complication of insulin therapy. The amyloid fibril protein is derived from the injected insulin and forms an amyloid deposit at the injection site [1,2]. The clini...

Objectives Insulin-derived amyloidosis is a rare skin-related complication of insulin therapy. The purpose of this study was to show the effects of insulin-derived amyloidosis on blood glucose levels, insulin dose requirements, and insulin absorption. Methods Seven patients were found to have insulin-derived amyloidosis at the Tokyo Medical University Ibaraki Medical Center. The clinical characteristics and insulin therapy of the 7 patients were investigated. Insulin absorption was studied by comparing the serum insulin levels after insulin injections into insulin-derived amyloidosis sites versus injections into normal sites in 4 patients. Results When the insulin-derived amyloidosis was discovered, the mean hemoglobin A1c level was 9.3%, and the mean daily insulin dose was 57 units. After changing the injection sites to avoid the insulin-derived amyloidosis, the blood glucose concentrations improved, and the mean daily insulin dose could be reduced to 27 units (P = .035; 53% reduction). The insulin absorption at insulin-derived amyloidosis sites was 34% of that at normal sites (P = .030). Conclusions Insulin-derived amyloidosis caused poor glycemic control and increased insulin dose requirements because of impairments in insulin absorption.

The chest radiograph of a 57-year-old man, complaining of paroxysmal dyspnea, suggested the probably of a tumor. Chest CT showed a tumor containing calcification, behind the left crus of the diaphragm. Chest MRI suggested lipid components and a cystic lesion within the tumor. Their findings were clinically compatible with posterior mediastinal teratoma. The pathological diagnosis of the surgically resected tumor was mature teratoma with neither malignant components nor thymic tissue. Study of past case reports suggests that posterior mediastinal teratomas should have less malignant characteristics than anterior mediastainal teratomas. Our case is the fifteenth case report in the Japanese literature, and accumulation of more cases is required.