Neurofibromatosis Type 1 and pancreatic islet cell tumours: an association which should be recognized.
A 75-year-old female with known NF-1 was being investigated for episodes of recurrent collapse. During one episode, she lost consciousness and on the arrival of the paramedics her capillary glucose was reported as 1.7 mmol/l: 1 mg intramuscular glucagon was administered and blood glucose was 2.7 mmol/l on admission to the Emergency Department, where she received intravenous dextrose. She described a 3-year history of episodes of collapse which begun with the onset of visual disturbance followed by the sensation of leg weakness. They occurred after fasting and her symptoms resolved on eating. The patient had a known diagnosis of aortic stenosis and a recent echocardiogram had shown an aortic valve area of 1 cm2, with a peak gradient of 57 mmHg. A gastrointestinal stromal tumour had been resected several years previously.

An inpatient 72-h fast was performed. The patient developed symptomatic hypoglycaemia with a blood glucose of 2.1 mmol/l some 12 h into the fast. A concomitant insulin was 82 pmol/l, C-peptide 0.81 nmol/l and β-hydroxybutyrate 0.9 mmol/l, with a plasma sulphonylurea screen which was negative. The IGF-2: IGF-1 ratio was below 10, excluding the probability of an IGF2-secreting tumour. These results confirmed the presence of endogenous hyperinsulinism according to recent guidelines.1,2 The patient was hypertensive and two sets of 24-h urinary collections showed elevated metadrenaline levels of 2.51 umol/24 h and 4.31 umol/24 h, respectively (laboratory upper limit of normal for urinary metadrenaline 1.40 umol/24 h).

An MRI scan with gadolinium showed …