The multiple endocrine neoplasia (MEN) syndromes were described early in this century 1 and subsequently were classified to 2 broad categories, MEN type 1 and MEN type 2. [2][3][4] The MEN syndromes are inherited as an autosomal-dominant trait. The MEN1 gene has been mapped to the centromeric area of chromosome 11. In MEN1 families, a deletional mechanism of the regulatory gene appears to be the base of the syndrome. We describe 2 cases (mother and daughter) with MEN type 1 caused by a new genetic mutation, which has not been described before.A 40-year-old woman presented with a 3-day history of headaches, blurred vision, and funny turns, culminating in loss of consciousness and a generalized tonic-clonic seizure. She was admitted to the accident and emergency department. She was given 5 mg diazepam intravenously to terminate the seizure; her Glasgow coma scale was 3; and she was intubated, ventilated, and referred to the intensive-care unit. On examination, her pulse rate was 110 beats/min and regular, blood pressure 140/60 mm Hg, and there was a generalized increase in the tone. The rest of the examination was unremarkable. Urea, electrolytes, and full blood count were within normal limits, glucose 12.1 mmol/L, corrected calcium 3.25 mmol/L (normal range, 2.13-2.63 mmol/L), phosphate 0.5 mmol/L (normal range, 0.80 -1.40 mmol/L), and parathyroid hormone level was arranged. Lumbar puncture, cerebrospinal fluid examination, and magnetic resonance imaging of the brain were within normal limits. She was treated with intravenous fluid, phenytoin, ceftriaxone, and metronidazole. She improved, woke up, and was extubated after 24 hours. However, she had recurrent hypoglycemic attacks and blood glucose was less than 2 mmol/L on several occasions. Despite a normal diet and frequent snacks, she continued to have frequent hypoglycemia attacks, and intravenous 10% dextrose was needed on several occasions.Parathyroid hormone was inappropriately high at 24.4 pmol/L (normal range, 1-7 pmol/L), and 24-hour urine calcium excretion 7.7 mmol/24 hours (normal range, 2.5-7.5 mmol/L). Isotope subtraction scan demonstrated a tumor in the lower pole of the thyroid. Insulin and C-peptide were inappropriately high; insulin 115 mu/L (normal, Ͻ10 mu/L) and C-peptide 805 pmol/L (normal, Ͻ94 pmol/L). C-peptide suppression test was performed using 6.5 units insulin intravenously, glucose decreased to 1.3 mmol/L, but there was no decrease in the C-peptide level. Thyroid function tests, growth hormone, IGF 1, cortisol, glucagons, neurotensin, pancreatic polypeptide, vasoactive intestinal peptide, folliclestimulating hormone, luteinizing hormone, basal gastrin and its response to calcium infusion were within normal limits. Magnetic resonance imaging of the abdomen and celiac artery angiography were normal. Portal vein sampling demonstrated the predominant source of insulin to be from the head of the pancreas. Laparoscopic ultrasound did not identify any pancreatic tumors. The diagnosis of mu1tiple endocrine neoplasia (MEN) type 1 with parathyroid...