Mental Retardation, X-Linked 105

A number sign (#) is used with this entry because of evidence that X-linked mental retardation-105 (MRX105) is caused by mutation in the USP27X gene (300975) on chromosome Xp11.

Clinical Features

Hu et al. (2016) reported 2 unrelated families (D177 and L75) in which a total of 7 males had borderline to moderate intellectual disability, variable poor or absent speech, and behavioral problems. No additional clinical details were provided.

Inheritance

The transmission pattern of MRX105 in the families reported by Hu et al. (2016) was consistent with X-linked recessive inheritance.

Molecular Genetics

In 3 affected males from a family (D177) with MRX105, Hu et al. (2016) identified a hemizygous truncating mutation in the USP27X gene (300975.0001). An unrelated male patient (family L75) with MRX105 was found to carry a hemizygous missense mutation in the USP27X gene (Y381H; 300975.0002); 3 others males in this family were affected, but genetic studies were not performed. Carrier females in both families were unaffected. The mutations were found by X-chromosome exome sequencing of 405 probands with X-linked intellectual disability. Functional studies of the variants were not performed.