Current insight in the localized insulin-derived amyloidosis (LIDA): clinico-pathological characteristics and differential diagnosis.

Background: In diabetic patients, subcutaneous insulin injection may cause several types of injection site-related lesions, such as lipoatrophy, insulin-induced cutaneous lipohypertrophy (IICL), allergic reaction, and iatrogenic localized insulin-derived amyloidosis (LIDA). Among these complications, both IICL and LIDA present as tumor-like and slow growing lesions; and they may be confused with one another. The clinical implication and management of IICL and LIDA are different. LIDA causes poor blood glycemic controls due to inadequate absorption of the insulin. Thus, accurate diagnosis of the lesion is critical in diabetic patients.

Review Of Literature: LIDA is an extremely rare complication and often overlooked, it is managed by a surgical intervention. Whereas, IICL is a common side effect and can be managed by a non-surgical approach. Furthermore, in long-standing diabetics, patients may develop hypertrophic cardiomyopathy, proteinuria, peripheral, and autonomic neuropathy; these symptoms can be mistaken for a systemic amyloidosis. It is also necessary to distinguish LIDA from the systemic amyloidosis, which requires a more aggressive systemic therapy. LIDA should also be distinguished from primary cutaneous amyloidosis, with high risk of progression to a systemic amyloidosis. In this effort we reviewed 25 published manuscripts, including case reports and case series studies. We also summarized the literature and discussed differential diagnosis, including the approach to diagnose LIDA.

Conclusion: The identification of amyloid material and immunoreactivity with anti-insulin antibodies are key diagnostic features of LIDA. Although several clinical and animal studies were made in recent years, the lesion is still under-diagnosed and underreported. The clinical suspicion and knowledge of the lesion play a crucial role for the accurate diagnosis of LIDA. Surgical excision of the lesion can dramatically decrease insulin requirement and improve glycemic control.