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The inheritance of Angelman's syndrome, a disorder characterised by mental retardation, epilepsy, ataxia, and a happy disposition, is debated because affected sibs occur less frequently than expected with autosomal recessive inheritance. After discovering two unrelated patients with a small deletion of the proximal long arm of chromosome 15, 10 further patients with Angelman's syndrome were reassessed. Five had apparently normal karyotypes, four had a deletion within 15q11-13, and one had a pericentric inversion, inv(15)(p11q13) involving the same chromosomal region. In the latter case, the healthy mother had the same pericentric inversion, indicating that the patient also had a submicroscopic mutation on his other chromosome 15. These data map the Angelman locus to 15q11-13 and suggest that de novo visible deletions (associated with a low recurrence risk) and autosomal recessively inherited cases combine to give an overall sib recurrence risk of less than 25%. [ABSTRACT FROM PUBLISHER]

The first ever antenatal diagnosis of Patau's syndrome (trisomy 13) during the 19th week of the pregnancy of a 42-year-old woman is reported. Karyotypes were obtained from amniotic fluid cell cultures established at 17 weeks and the results were confirmed by chromosome banding studies and fetal skin cultures. The pregnancy was terminated by hysterotomy and sterilization was performed at the same operation. A detailed description of the fetus is included and the pathogenesis of arrhinencephaly is discussed. The current status of antenatal screening for chromosome anomalies is presented. [ABSTRACT FROM PUBLISHER]