Congenital hyperinsulinism in two siblings with ABCC8 mutation: same genotype, different phenotypes

SUMMARY Congenital hyperinsulinism (CHI) is a heterogenous disease caused by insulin secretion regulatory defects, being ABCC8/KCNJ11 the most commonly affected genes. Therapeutic options include diazoxide, somatostatin analogues and surgery, which is curative in focal CHI. We report the case of two siblings (born two years apart) that presented themselves with hypoketotic hyperinsulinemic persistent hypoglycemias during neonatal period. The diagnosis of diffuse CHI due to an ABCC8 compound mutation (c.3576delG and c.742C>T) was concluded. They did not benefit from diazoxide therapy (or pancreatectomy performed in patient number 1) yet responded to somatostatin analogues. Patient number 1 developed various neurological deficits (including epilepsy), however patient number 2 experienced an entirely normal neurodevelopment. We believe this case shows how previous knowledge of the firstborn sibling's disease contributed to a better and timelier medical care in patient number 2, which could potentially explain her better neurological outcome despite their same genotype.

Association study of the ABCC8 gene variants with type 2 diabetes in south Indians.

BACKGROUND: The ABCC8 gene which encodes the sulfonylurea receptor plays a major role in insulin secretion and is a potential candidate for type 2 diabetes. The ‑3c → t (rs1799854) and Thr759Thr (C → T, rs1801261) single nucleotide polymorphisms (SNPs) of the ABCC8 gene have been associated with type 2 diabetes in many populations. The present study was designed to investigate the association of these two SNPs in an Asian Indian population from south India. MATERIALS AND METHODS: A total of 1,300 subjects, 663 normal glucose tolerant (NGT) and 637 type 2 diabetic subjects were randomly selected from the Chennai Urban Rural Epidemiology Study (CURES). The ‑3c → t and Thr759Thr were genotyped in these subjects using polymerase chain reaction‑restriction fragment length polymorphism (PCR‑RFLP) and a few variants were confirmed by direct sequencing. RESULTS: The frequency of the ‘t’ allele of the ‑3c → t SNP was found to be 0.27 in NGT and 0.29 in type 2 diabetic subjects (P = 0.44). There was no significant difference in the genotypic frequency between the NGT and type 2 diabetic group (P = 0.18). Neither the genotypic frequency nor the allele frequency of the Thr759Thr polymorphism was found to differ significantly between the NGT and type 2 diabetic groups. CONCLUSION: The ‑3c → t and the Thr759Thr polymorphisms of the ABCC8 gene were not associated with type 2 diabetes in this study. However, an effect of these genetic variants on specific unidentified sub groups of type 2 diabetes cannot be excluded.

Characterization of the ABCC8 gene mutation and phenotype in patients with congenital hyperinsulinism in western Saudi Arabia

To understand the genetic etiologies of congenital hyperinsulinism [CHI] in a population of Saudi patients, and to explore genotype-phenotype characteristics. We retrospectively reviewed a cohort of 11 children with CHI presenting to King Abdulaziz University Hospital, Jeddah, Kingdom of Saudi Arabia between March 2007 and February 2012. Mutational analysis [ABCC8 and KCNJ11] was performed retrospectively to identify phenotype and genotype characteristics. Analysis revealed ABCC8 mutations in 81.8% [9/11] of patients, with 2 patients not revealing any gene mutation. All positive patients showed a homozygous mutation in the ABCC8 gene, one in exon 29, 2 in exon 1-22, 2 in exon 28, and 4 in intron 36; one patient had a heterozygous mutation. Five patients [45.4%] responded well to treatment with diazoxide not requiring subtotal pancreatectomy, while 6 patients [54.6%] required subtotal pancreatectomy despite treatment with diazoxide and octreotide. Three patients [33.3%] died while waiting for surgery due to sepsis and thrombosis. Two patients [18.1%] showed remission, one of them after subtotal pancreatectomy. Homozygous mutations in ABCC8 are the most common causes of CHI in Saudi patients. Early diagnosis and therapy for persistent hyperinsulinemic hypoglycemia of infancy are essential to prevent neurodevelopmental delay