A three-year-old Chinese girl presented with hyperammonemia was diagnosed biochemically and genetically (heterozygous for a novel likely pathogenic missense variant c.476T>A) as having ornithine transcarbamylase (OTC) deficiency, a rare X-linked recessive urea cycle disorders. Extensive family genetic screening eventually revealed paternal gonadosomatic mosaicism.
Keywords: genetic mosaicism; hyperammonemia; inborn errors of metabolism; ornithine transcarbamylase deficiency.
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