Mutational analysis of the GYS2 gene in patients diagnosed with ketotic hypoglycaemia.

BACKGROUND:Ketotic hypoglycaemia is a common form of hypoglycaemia in childhood. Biochemically, patients present with fasting hypoglycaemia but with normal hormonal and metabolite profiles (low serum alanine levels in some patients). Glycogen Storage Disease Type 0 (GSD0) is an autosomal recessive disease due to mutations in the GYS2 gene. Patients with GSD0 also present with fasting ketotic hypoglycaemia. The frequency of GSD0 in patients presenting with ketotic hypoglycaemia is not known. OBJECTIVE:To understand the frequency of GSD0 in patients presenting with ketotic hypoglycaemia and to report a novel mutation in the GYS2 gene. SUBJECTS:The GYS2 gene was sequenced in 50 patients diagnosed with ketotic hypoglycaemia. METHODS:All exons (including exon and intron boundaries) of the GYS2 gene were sequenced following amplification of the coding region by polymerase chain reaction (PCR). RESULTS:No mutations in GYS2 were found in 49 patients. One patient had a novel homozygous mutation (c.1802T>G; p. Leu601X) in exon 14 of the GYS2 gene. We believe this is the 18th mutation reported so far. This mutation is predicted to lead to premature truncation of the glycogen synthase protein with no function. This patient presented with fasting ketotic hypoglycaemia associated with postprandial hyperglycaemia and elevated lactate level. CONCLUSIONS:GSD0 is relatively rare in patients presenting with ketotic hypoglycaemia and a normal biochemical profile. Sequencing of the GYS2 gene is more likely to be positive in patients with fasting ketotic hypoglycaemia and concomitant postprandial hyperglycaemia with hyperlactataemia.

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