Rett syndrome (RTT) is an X-linked condition which affects almost exclusively females.
Here we report the first case of RTT syndrome in a boy with an XXY chromosomal constitution.
Mutation analysis of the MECP2 gene in the affected patient revealed a 423 C→G substitution
in exon 4, resulting in a new stop codon (Y141 X). This change was not present in
both his parents or in his older sister. Taking into account the incidence of both
RTT syndrome as well as of Klinefelter syndrome, the probability for the simultaneous
occurrence of these two events is very low (about ∼ 1 in 10 to 15,000,000 births).
However, the recent identification of mutations in the MECP2 gene in affected males
indicates that screening of the MECP2 gene should be considered also in males with
severe mental retardation (MR) in whom the most common forms of MR have been excluded.
Key words
Rett syndrome - XXY karyotype - MECP2 mutation
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Professor of Genetics Dr. Mayana Zatz
Centro de Estudos do Genoma Humano Departamento de Biologia Instituto de Biociências
Universidade de São Paulo
CEP: 05508-900
São Paulo, SP
Brazil
eMail: mayazatz@usp.br