Tetrasomy 9p confirmed by GALT.

We report a boy aged 12 years 7 months with mental retardation, hydrocephalus, dysmorphic facial features, congenital heart disease, and skeletal and renal anomalies. The karyotype showed a mosaic tetrasomy 9p involving the secondary constriction. This result was confirmed by tetraplex gene dosage effect for galactose-1-P-uridyltransferase (GALT). Comparing the clinical features of our case with those of previously reported patients, tetrasomy 9p appears to be a distinctive and clinically recognisable malformation syndrome.