Long term outcome in children of sex chromosome abnormalities
- Little Browns Cottage, Honeypot Lane, Edenbridge, Kent TN8 6QJ, UK
- Dr Ratcliffe.
An unduly pessimistic description of what it means to have an extra X or Y chromosome is frequently given to the parents of an affected fetus or child by geneticists and paediatricians because the source of their information has been biased towards abnormality. In 1967 the Medical Research Council set up a cytogenetic survey of consecutive newborn infants to establish the incidence of the various chromosome abnormalities. The long term follow up of children with sex chromosome abnormalities ascertained in the survey, which screened 34 380 newborns in Edinburgh between 1967 and 1979, has enabled a more balanced prognosis to be reached.
Most boys with the karyotypes 47,XXY and 47,XYY and girls with 47,XXX are never diagnosed. While that may suggest that the conditions are of no importance to the affected individuals, I will show using the following results that this is not the case.
Based on the incidence at birth obtained from cytogenetic surveys of around 200 000 infants from the UK, Denmark, Canada, the USA, and Japan, an XXY karyotype was found in 1.3 per 1000 male infants, while XYY and XXX occurred with a frequency of 1 per 1000 male or female infants, respectively.1 Using these incidence figures Abramsky and Chapelle2 found that 10% of expected cases of XXY boys were identified at amniocentesis, a further 26% were diagnosed in childhood or adult life on account of hypogonadism, gynaecomastia, infertility, or developmental delay, leaving 64% undiagnosed. Among XYY boys, where there is no advanced paternal age effect, 85% were calculated to be undiagnosed either before or after birth. Abramsky and Chapelle did not include XXX females, but an estimate can be made from the maternal age distribution of 57 affected newborns where 26% were born to mothers over the age of 35 years. It is reasonable to …