18F-DOPA PET/MRI With Carbidopa for the Diagnosis of Hyperinsulinemic Hypoglycemia in an Adolescent Patient.

ABSTRACT

Hyperinsulinism due to focal or diffuse pancreatic lesions causing recurrent episodes of hypoglycemia is rare in mid-childhood. There is no consensus on the gold-standard imaging method to diagnose focal insulin-producing lesions beyond infancy. A 14-year-old boy with a complex medical history and refractory epilepsy, presented with blood glucose (BG) of 52 mg/dL (2.9 mmol/L) (normal reference range 70-100 mg/dL [3.9-5.6 mmol/L]) and increased seizure frequency. He failed a fast within 4 hours, with BG of 48 mg/dL (2.7 mmol/L) and insulin level of 4.6 µIU/mL (24.6 pmol/L) (diagnostic at the time of hypoglycemia >1.25 µU/mL [8.7 pmol/L]). Conventional imaging studies showed no pancreatic lesion. Fluorine-18-L-dihydroxyphenylalanine positron emission tomography/magnetic resonance imaging (18F-DOPA-PET/MRI) scan premedicated with carbidopa demonstrated intense focal 18F-DOPA uptake in the distal pancreatic tail. He underwent distal pancreatectomy. Histopathology showed focal pancreatic islet cell hyperplasia, with more than 90% of the neuroendocrine islet cells being positive for chromogranin and synaptophysin, with no loss of p57 staining. Genetic studies were negative for mutations in ABCC8, KCNJ11, GCK, or GLUD1 genes, multiple endocrine neoplasia (MEN) type 1, and Beckwith-Wiedemann syndrome. BG normalized after surgery. Seizure frequency improved. This case highlights the utility of 18F-DOPA PET/MRI imaging in diagnosing focal hyperinsulinism beyond infancy.