We describe the clinical and molecular features of a child harboring a novel mutation in SLC6A8 gene in association with a milder phenotype than other creatine transporter (CT1) deficient patients (OMIM 300352) [1-7]. The mutation c.757 G>C p.G253R in exon 4 of SLC6A8 was hemizygous in the child, aged 6 years and 6 months, who showed mild intellectual disability with severe speech and language delay. His carrier mother had borderline intellectual functioning. Although the neurochemical and biochemical parameters were fully consistent with those reported in the literature for subjects with CT1 deficit, in our patient within a general cognitive disability, a discrepancy between nonverbal and verbal skills was observed, confirming the peculiar vulnerability of language development under brain Cr depletion.
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