Occurs in about one out every 1000 male births. Advanced maternal age appears to be a risk factor. Clinically, the condition is usually considered when a boy presents with clumsiness or mild learning difficulties. The overall verbal IQ is reduced by about 10-20 points below unaffected boys. Adults with Klinefelters tend to be taller than average with long lower limbs.
Infertility is typical.
Occurs in 1 of every 5000 or 10,000 live female births. Turners syndrome is occasionally identified by ultrasound during the second trimester. At birth, some babies appear entirely normal. Others have edema of hand and feet and webbing of the neck. Later, individuals with Turner syndrome have short stature and widely spaced nipples along with neck webbing.