De novo MECP2 disomy in a Mexican male carrying a supernumerary marker chromosome and no typical Lubs syndrome features

• Reporting a de novo gain Xq28 including MECP2 gene.
• Reporting de first case of Xq28 duplication syndrome due to sSMC.
• MECP2 duplication in this patient do not evoke Lubs syndrome.
• The clinical spectrum of MECP2 duplication is highly variable.
• The mosaicism of the sSMC is modifying the clinical features.

Xq28 duplication, including the MECP2 gene, is among the most frequently identified Xq subtelomeric rearrangements. The resulting clinical phenotype is named Lubs syndrome and mainly consists of intellectual disability, congenital hypotonia, absent speech, recurrent infections, and seizures. Here we report a Mexican male patient carrying a supernumerary marker chromosome with de novo Xq28 gain. By MLPA, duplication of MECP2, GDI1, and SLC6A8 was found and a subsequent a-CGH analysis demonstrated that the gain spanned ~ 2.1 Mb. Despite gain of the MECP2 gene, the features of this patient do not evoke Lubs syndrome. Probably the mosaicism of the supernumerary marker chromosome is modifying the phenotype in this patient.