Rett syndrome (RS [MIM 312750]) is a progressive encephalopathy characterized by severe mental retardation, autism, apraxia, seizures, stereotypical hand movements, and deceleration of head growth. Its prevalence is estimated at 1: 10,000–15,000 female births (Hagberg 1995). The majority of cases are sporadic, but rare reports of familial recurrence have been made. In addition, all but 1 of the 10 MZ twins reported in the literature are concordant, whereas all 11 DZ twins reported are discordant for the disorder (Migeon et al. 1995). Laboratory investigations have not revealed any metabolic abnormalities in affected individuals. Chromosomal abnormalities and/or association with another syndrome have already been reported in patients with RS: a translocation t (X; 22)(p11. 22; p11) by Journel et al.(1990), a translocation t (X; 3)(p21. 3; p25. 2) by Zoghbi et al.(1990) and Ellison et al.(1993), a deletion del (3)(3p25. 1-p25. 2) by Wahlstrom et al.(1996), and a deletion del (13)(13q12. 1-q21. 2) by Herder et al.(1996). RS was described in association with fragile X by Alembick et al.(1995) and with Down syndrome by Easthaugh et al.(1996). No concordance for the chromosomal abnormalities has been found, however, since different chromosomes and/or breakpoints were involved in each case. Vorsanova et al.(1996) reported a boy with RS and karyotype 46, XY/47, XXY (the 47, XXY cell line was observed in 6%–12% of the studied lymphocytes).

Here, we describe a patient with RS and a 47, XXY karyotype. The propositus, a male patient born in January 1995, was referred for genetic studies at age 28 mo. His parents are healthy, were aged 30 years (father) and 29 years (mother) at the time of the birth, and are not consanguineous. The child was born at term, after an uneventful pregnancy. His birth weight was 3.330 g (25th–50th percentile), his Apgar indices were 6 (1st minute) and 7 (5th minute), and his birth occipitofrontal head circumference was 32 cm (2.5 percentile). The perinatal period was uneventful. The propositus is the