Prevalence Estimation of Williams Syndrome

TLDR

Population-based data on the occurrence of Williams syndrome are limited. The study estimated its prevalence by combining data from two investigations. The authors used an epidemiologic study of 30,037 Norwegian children and a national survey of 57 Williams syndrome cases to assess prevalence. They found three cases in the epidemiologic study and one additional case in the national survey, yielding a prevalence of 1 in 7,500 and indicating that Williams syndrome accounts for about 6% of genetic causes of mental retardation, with all cases showing a typical chromosome 7q11.23 deletion. J Child Neurol 2002;17:269-271.

Abstract

There are limited population-based data on the occurrence of Williams syndrome. We estimated its prevalence combining data from two investigations. One was an epidemiologic study originally designed to assess the prevalence and etiology of mental retardation among 30,037 Norwegian children born between 1980 and 1985 and living in Akershus County on January 1, 1993. The other investigation was a national survey of Williams syndrome. In the first study, 213 children were referred for evaluation, whereas the second study comprised 57 cases with Williams syndrome born between 1970 and 1992, who were referred for evaluation from all Norwegian counties. The epidemiologic study revealed three children with Williams syndrome, whereas one additional case complying with our demographic criteria was identified in the national survey, thus giving a prevalence of 1 in 7500. In all cases, a typical chromosome 7q11.23 deletion was detected. We also conclude that Williams syndrome is not an uncommon cause of mental retardation, with a prevalence of approximately 6% of patients with genetic etiology. (J Child Neurol 2002;17:269-271).