Familial 1.1 Mb deletion in chromosome Xq22.1 associated with mental retardation and behavioural disorders in female patients

We report on a 7-year-old girl with severe mental retardation (MR), autism, micro-brachycephaly, generalized muscle hypotonia with distal hypotrophy of lower limbs, scoliosis and facial dysmorphisms. Array-CGH analysis identified a 1.1 Mb deletion of chromosome Xq22.1. Further analysis demonstrated that the deletion was inherited from her mother who showed mild MR, short stature, brachycephaly, epilepsy and a Borderline Personality Disorder. Microsatellite segregation analysis revealed that the rearrangement arose de novo in the mother on the paternal X chromosome. The deleted Xq22.1 region contains part of the NXF gene cluster which is involved in mRNA nuclear export and metabolism. Among them, the NXF5 gene has already been linked to mental retardation whereas NXF2 protein has been recently found to be partner of FMRP in regulating Nxf1 mRNA stability in neuronal cells. The dosage imbalance of NXF5 and NXF2 genes may explain the severe phenotype in our patient.