A Case Report of Insulinoma Relapse on Background Nesidioblastosis: A Rare Cause of Adult Hypoglycemia

Context: Nesidioblastosis is a rare cause of adult hypoglycemia. Current medical therapy can mitigate disease symptoms. However, side effects and limited efficacy may prevent long-term disease management.Case Description: A 63-year-old white woman presented at our institution on April 2017 with a history of distal spleno-pancreatectomy for well-differentiated insulinoma in 2013. Hypoglycemic events did not resolve after surgery, and residual nesidioblastosis near the pancreatic resection margins was identified. Hypoglycemic episodes increased in frequency and severity despite high-dose diazoxide (DZX) therapy. On April 2016, octreotide was introduced but soon discontinued for inefficacy. When the patient arrived at our attention, add-on pasireotide was started and glucose levels monitored by subcutaneous sensor. Compared with DZX, 225 mg/d alone, sensor glucose during pasireotide + DZX 75 mg/d showed occurrence of severe hypoglycemia. Pasireotide was discontinued, and the instrumental workup (Ga-68-DOTATOC CT/positron emission tomography, Tc-99m-nanocolloid scintigraphy and echo-endoscopy + fine-needle aspiration biopsy) identified an insulinoma relapse. Subtotal pancreatectomy was performed without further recurrence of hypoglycemia over 9 months of follow-up.Conclusions: Although insulinoma relapses on background nesidioblastosis rarely occur, they should be considered as an alternate diagnosis when medical therapy fails to prevent hypoglycemia. Further studies are warranted to test whether the immunophenotypic signature of nesidioblastosis/insulinoma may provide insights for a tailored use of pasireotide.