Endocrine Abstracts

Insulin-derived amyloidosis is a rare form of localised amyloidosis resulting from the aggregation of exogenous insulin into subcutaneous amyloid fibrils at injection sites. Although its true prevalence remains unknown, increasing evidence suggests it is underdiagnosed and often mistaken for lipohypertrophy. We report the case of a 68-year-old Irish male with longstanding type 2 diabetes mellitus, managed with subcutaneous insulin for over 20 years—initially via continuous subcutaneousinsulin infusion(2003–2022), and subsequently with a basal-bolus regimen(2022–present). Despite escalating insulin doses due to significant insulin resistance, his diabetes control has been deteriorating(HbA1c ). Work up for systemic amyloidosis was initiated due to constellation of symptoms such as subcutaneous abdominal masses, autonomic dysfunction, upper limb sensory symptoms, and heart failure due to hypertrophic cardiomyopathy. A subcutaneous fat biopsy performed on 8th January 2025 confirmed amyloid deposits via Congo red staining and mass spectrometry. Subsequently the patient has been diagnosed with insulin-derived amyloidosis. The patient has been educated regarding the importance of rotating injection sites and his HbA1c has improved from 77 to 55 over a few months and he is requiring lower doses of insulin. Repeated insulin injections at the same site can lead to amyloid formation, contributing to poor glycaemic control and unpredictable hypoglycaemic episodes. Treatment strategies include rotation of injection sites and, in some cases, surgical excision of amyloid masses. This case highlights the importance of clinical suspicion for insulin-derived amyloidosis in patients with unexplained insulin resistance and subcutaneous masses, particularly in those with long-term insulin therapy.