Analysis of Human Genetic Linkage

We report here a female patient with Williams syndrome who showed typical dys- morphic features, a characteristic personal- ity, and bilateral renal artery stenosis.This patient has an apparently balanced reciprocal translocation involving chromosomes 1 and 18: 46,XX,t(1;18)(q12;q23).Thus the break- point of chromosome 18 in band q23 is in the same band as in the patient reported by Colley et al.5 The father of the present patient carries the same balanced transloca- tion and is apparently healthy.Studies of this chromosome region at DNA level are cur- rently being performed.We conclude that there are now two patients with Williams syndrome showing a chromosomal rearrangement involving 18q23.On one hand a gene defect at a locus at 18q23 might lead to a phenocopy of Wil- liams syndrome.Alternatively, patients with the Williams syndrome not showing any chromosomal abnormality might have a submicroscopic deletion or a mutation located at 18q23, or an anomaly of genomic imprinting might be involved.