Endocrine Abstracts

Introduction: Congenital hyperinsulinism (CHI) is a rare disease characterized by an unregulated insulin release, leading to hypoglycaemia. It is the most frequent cause of persistent and severe hypoglycaemia in the neonatal period and early childhood. FOXA2, a beta-cell transcription factor is localized at the cytogenetic location 20p11.2 and is critical for the development of pancreas and pituitary gland. We describe a child with 20p11.21 deletion encompassing heterozygous whole gene deletion FOXA2 causing congenital hyperinsulinism with potential pituitary involvement.

Case: Our patient, a 3-year-old girl, was born to non-consanguineous parents at 39-week gestation with a birth weight of 2.82 kg presented with seizures at 45 hours of age. Her blood glucose was <0.3mmol/L with an inappropriately elevated plasma insulin of 209pmol/L and an inappropriately supressed β- hydroxybutyrate and free fatty acids consistent with the diagnosis of CHI. Her maximum glucose infusion rate was 20mg/kg/minute. She responded to diazoxide with a maximum dose of 9mg/kg/day. Further investigations included a CGH microarray which showed a 8.3Mb deletion of the short arm of chromosome 20 at 20p12.1p11.21. As this area encompasses FOXA2, subsequent tests confirmed a heterozygous FOXA2 whole gene deletion arising de-novo. Extra pancreatic features in our patient include a subtle dysmorphism, ventricular septal defect, horseshoe shaped kidney and developmental delay involving speech. The baseline pituitary screen included a normal cortisol of 402 nmol/L and normal thyroid function test. During the recent clinic review, at the age of 3, she continues to require diazoxide at a dose of 7 mg/kg/day. Her height velocity was noted to have declined to the 3rd centile with a low IGF1 which is likely to be an evolving growth hormone deficiency. A growth hormone stimulation test and an MRI pituitary gland to look for any structural pituitary abnormalities is being planned.

Discussion: Deletions involving the cytogenic location 20p11.2 band can cause hyperinsulinism as this area encompasses FOXA2. The phenotype can extend to affect the pituitary gland and hence regular assessment of pituitary function along with imaging to look for pituitary structural anomalies is important.