Later-onset congenital central hypoventilation syndrome due to a heterozygous 24-polyalanine repeat expansion mutation in the PHOX2B gene

Repetto, G. M.; Corrales, R. J.; Abara, S. G.; Zhou, L.; Berry-Kravis, E. M.; Rand, C. M.; Weese-Mayer, D. E.

Acta Paediatr. 2008 Sep 19; 98(1):192-5

Abstract

AIM: to describe a family with later onset congenital central hypoventilation syndrome (LO-CCHS) and heterozygosity for a 24-polyalanine repeat expansion mutation in the PHOX2B gene, rendered phenotypically apparent with exposure to anesthetics. CASE SUMMARY: An otherwise healthy 2.75-year-old boy presented with alveolar hypoventilation after adenoidectomy and tonsillectomy for obstructive sleep apnea, requiring invasive ventilatory support during sleep. He had a heterozygous 24-polyalanine repeat expansion in the PHOX2B gene (20/24 genotype), a genotype that has not been previously described in association with CCHS or LO-CCHS symptoms. Clinical findings in members of the family with the same 20/24 genotype ranged from asymptomatic to prolonged sedation after benzodiazepines. CONCLUSION: CCHS should be suspected in individuals presenting with unexplained hypoventilation and/or seizures after anesthetics or sedatives. This is the first report of LO-CCHS in a kindred with the PHOX2B 20/24 genotype. The incomplete penetrance observed in this family suggests a gene-environment interaction.

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