Hunting for a hypoglycemia gene: Severe neonatal hypoglycemia in a consanguineous family

Hypoglycemia is a dreaded complication in diabetes mellitus patients treated with insulin, but is also a symptom that is observed in many disorders. In some metabolic diseases of early infancy, low blood glucose is the major presentation and the condition can become life-threatening. Such cases are often attributed to inherited hyperinsulinism. Vidnes and Oyasaeter [1977: Pediatr Res 11:943-949] described a son of consanguineous Pakistani parents with severe neonatal hypoglycemia and concluded that the patient probably suffered from an isolated glucagon deficiency. We have continued the investigation of this family, which now includes a hypoglycemic daughter and two healthy children. The original diagnosis is questioned because the second case of hypoglycemia can be explained by hyperinsulinism. We proceeded with microsatellite marker analysis for selected candidate genes under the assumption that the condition is autosomal recessive and that affected children are homozygous for a mutated allele. The four known genetic causes for inborn hyperinsulinism (mutations in the genes ABCC8, KCNJ11, GLUD1, and GCK) were excluded. Furthermore, we eliminated 13 candidate genes coding for transcription factors involved in pancreas development and differentiation. The analysis was also negative for the genes encoding insulin and glucagon, their receptors, and processing enzymes. The identification of a novel gene for persistent neonatal hypoglycemia can be expected to yield fundamental information about glucose homeostasis, and will therefore have implications, for the understanding of diabetes as well. (C) 2002 Wiley-Liss, Inc.