We describe the case of a 26 year old female who presented with 6 months of symptomatic reactive hypoglycaemia. She had intentionally lost 25kg in weight over the preceding 5 years through diet and exercise but had not undergone bariatric surgery. At 60 minutes after a mixed meal, plasma glucose fell to 2.0 mmol/L with insulin 6.1 mU/L and C-peptide 1.4 nmol/L, consistent with insulin-mediated reactive hypoglycaemia. Interestingly, a 72 hour fast was also positive with symptomatic hyperinsulinaemic hypoglycaemia developing after 29 hours with a plasma glucose of 2.1 mmol/L, insulin 5.0 mU/L, C-peptide 0.5 nmol/L and pro-insulin 17.9 pmol/L. Extensive pancreatic imaging failed to reveal a mass lesion but selective arterial calcium stimulation (SACS) testing localised abnormal beta cells to the proximal splenic artery territory with a four-fold rise in insulin levels from 8.2 mU/L at baseline to 36 mU/L at 60 seconds. Medical therapy with diazoxide was unsuccessful and she finally underwent a subtotal distal pancreatectomy. Histopathological examination of the resected pancreas was consistent with nesidioblastosis.

This is a case of Non-insulinoma Pancreatogenous Hypoglycaemia Syndrome (NIPHS) due to nesidioblastosis, a relatively uncommon but increasingly recognised condition accounting for 0.5 to 7% of cases of adult persistent hyperinsulinaemic hypoglycaemia. (1,2) NIPHS is described as postprandial (reactive) hypoglycaemia without evidence of an insulinoma but with histopathological features of islet cell hypertrophy or nesidioblastosis. (3,4) The cause of adult NIPHS has not been clearly established but there is an association with Roux-en-Y Gastric Bypass Surgery.  (5,6) Our case is unusual as the patient had both reactive and fasting hypoglycaemia, in addition to having a history of significant non-surgical weight loss. Furthermore, SACS testing clearly localised an abnormal area of pancreas even though diffuse pancreatic involvement is more expected.

The evaluation and management of this patient will be discussed in relation to the available literature.