Halil İbrahim AYDIN, Fatma Müjgan SÖNMEZ

A novel mutation in two cousins with guanidinoacetate methyltransferase (GAMT) deficiency presented with autism

Guanidinoacetate methyltransferase (GAMT) deficiency is a rare autosomalrecessive disorder of creatine biosynthesis. Here, we report 9 and 10-year-oldcousins with GAMT deficiency caused by a novel mutation who both exhibitedneurodevelopmental retardation, seizures, behavioral problems, and autismthat began during early infancy. The patients were diagnosed as having onlyautism and followed for years without a specific diagnosis although theyhad very low levels of serum creatinine for several times. A novel nonsensemutation in the GAMT gene that caused cessation of synthesis of the proteinencoded by this gene was identified in these patients. GAMT deficiency is atreatable inborn error of metabolism and should be considered for all patientswith hypotonia, developmental delay, seizures and autism, particularly if lowserum creatinine levels are observed.

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