An Atypical Presentation of Insulin Amyloidosis: An Uncommon but Important Complication of Insulin Therapy

ABSTRACT Objective: To describe a case of insulin amyloidosis that highlights an uncommon but significant complication of subcutaneous insulin therapy. Methods: We review the case of a patient with type 2 diabetes mellitus on long-standing insulin therapy with insulin amyloid deposits found at the insulin injection sites and the possible clinical complications associated with this condition. Results: A fat-pad aspirate of the abdomen, which was performed for the evaluation of worsening renal function, was positive for Congo red staining. Further subtype analysis via liquid chromatography in tandem with mass spectrometry revealed a peptide profile of insulin-derived amyloid deposition. Conclusions: Insulin amyloid is a less common but important complication of insulin therapy. Often patients will present with dermatologic changes at the site of insulin amyloid deposition, however some have faint (as in our patient) or no physical changes on exam. It is important for clinicians to be aware of this condition, not only to educate patients on proper insulin administration, but also to be aware of conditions which can influence insulin pharmacokinetics. Abbreviation: AIns insulin-derived amyloid deposition