Abstract
To date, almost all case reports of insulin-derived amyloidosis described the presence of a subcutaneous mass that was observable on physical examination. This report presents two cases of insulin-derived amyloidosis without palpable masses at insulin injection sites. In both cases, blood glucose concentrations improved, and the insulin dose could be reduced by an average of 45% after changing the insulin injection sites. The insulin absorption at the site was reduced to at most 40% of that at a normal site in one case. Magnetic resonance imaging and ultrasonography were useful to screen and differentiate insulin-derived amyloidosis without a palpable mass. This report showed that insulin-derived amyloidosis without a palpable mass can be present at the insulin injection site, and has similar clinical effects to insulin-derived amyloidosis with palpable masses.