Expansion of the phenotypic spectrum in three families of methyl CpG-binding protein 2 duplication syndrome.

The methyl CpG-binding protein 2 duplication syndrome (OMIM #300260) is characterized by hypotonia, developmental delay, spasticity, seizures, and recurrent infections. It is fully penetrant in males and the females can have varied manifestations because of skewed X-inactivation. The size of the duplication can range from 0.2 Mb to over 100 Mb. Around 150 cases have been reported in the literature so far. Here, we report the unusual findings in three cases such as hepatomegaly, ataxia and females with mild intellectual disability that further expand the phenotypic spectrum of this disorder. This paper also stresses the need to perform microarray and/or multiplex ligation probe amplification in all cases of nonspecific intellectual disability.