Insulin Autoimmune Syndrome: Imaging Findings and Uptake Pattern With 68 Ga-Exendin-4 and 68 Ga-DOTATATE PET-CT

Area of Science:

• Endocrinology
• Nuclear Medicine
• Oncology

Background:

• Insulin autoimmune syndrome (IAS) is a rare cause of hypoglycemia.
• Distinguishing IAS from insulinoma can be challenging.
• Advanced imaging may aid in IAS diagnosis.

Purpose of the Study:

• To report a case of IAS diagnosed using Gallium-68 Exendin-4 PET/CT.
• To describe the characteristic imaging findings of IAS on Exendin-4 PET/CT.

Main Methods:

• A 62-year-old woman with hypoglycemia underwent prolonged fasting tests, abdominal CECT, and PET/CT scans (68Ga-Exendin-4 and 68Ga-DOTATATE).
• Blood tests confirmed elevated insulin and C-peptide levels and positive anti-insulin antibodies.

Main Results:

• CECT showed an isodense focus in the pancreatic tail.
• 68Ga-Exendin-4 PET/CT revealed diffuse tracer uptake throughout the pancreas.
• 68Ga-DOTATATE PET/CT showed physiological pancreatic uptake.

Conclusions:

• Gallium-68 Exendin-4 PET/CT can be a valuable tool for diagnosing insulin autoimmune syndrome.
• The diffuse pancreatic uptake pattern on 68Ga-Exendin-4 PET/CT is characteristic of IAS.