Adult hyperinsulinaemic hypoglycaemia caused by coexisting nesidioblastosis and insulinoma
Nesidioblastosis is derived from the Greek 'nesisidia' for islets and 'blastos' for germ. This term was introduced by Laidlaw in 1938, to define the pathological condition causing diffuse proliferation of pancreatic islet cells budding from ductal epithelium [G.F. Laidlaw. Nesidioblastoma, the islet tumour of the pancreas. Am J Pathol 1938;14:125-134]. It is widely recognised to be the primary cause of persistent hypoglycaemic hyperinsulinaemia in infancy (PHHI) but is rare in adults, representing 0.5-5% of cases of organic hyperinsulinaemia [S.S. Fajans, A.I. Vinik. Insulin-producing islet cell tumours. Endocrinol Metab Clin North Am 1989;18(1):45-74]. Insulinomas are neuroendocrine tumours derived from the pancreatic islet cells which produce excessive amounts of insulin. The vast majority are benign and 10% are multiple. Insulinoma though more frequent than nesidioblastosis, remains a rare entity, with an incidence of 4 cases per one million people per year. Differentiating between insulinoma and nesidioblastosis is difficult, clinically and biochemically. The treatment for the two conditions differs and it is of vital importance to pursue all avenues of investigation to differentiate them. Even then, the differentiation may be impossible. In the very rare instance, an insulinoma may coexist with nesidioblastosis. We report of such a case in a 38 year lady who presented with acute psychotic behaviour and was committed to a mental health institution. She was subsequently detected to have underlying recurrent hypoglycaemia. Blood glucose testing revealed a glucose level of 1.6 mmol/L, which was confirmed with a laboratory blood test, where serum glucose was noted to be 1.7 mmol/L. All preoperative efforts at obtaining diagnostic imaging of an insulinoma through CT scan, MRI scan and endoscopic ultrasound were unsuccessful. At surgery, she was detected to have both an insulinoma in the tail end of the pancreas and nesidioblastosis affecting the remainder of the pancreas. The coexistence of these rare diseases is very rare. A subtotal pancreatectomy corrected the hypoglycaemia and the patient has remained free of symptoms of since.