Estimates of the Apert syndrome birth prevalence and the mutation rate are reported for Washington State, Nebraska, Denmark, Italy, Spain, Atlanta, and Northern California. Data were pooled to increase the number of Apert births (n = 57) and produce a more stable birth prevalence estimate. Birth prevalence of the Apert syndrome was calculated to be approximately 15.5/1,000,000 births, which is twice the rate determined in earlier studies. The major reason appears to be incomplete ascertainment in the earlier studies. The similarity of the point estimates and the narrow bounds of the confidence limits in the present study suggest that the birth prevalence of the Apert syndrome over different populations is fairly uniform. The mutation rate was calculated to be 7.8 x 10(-6) per gene per generation. Apert syndrome accounts for about 4.5% of all cases of craniosynostosis. The mortality rate appears to be increased compared to that experienced in the general population; however, further study of the problem is necessary.

Cohen Jr MM, Kreiborg S. Birth prevalence studies of the Crouzon syndrome: comparison of direct and indirect methods. Clin Genet 1992: 41: 12–15. An indirect method for estimating the birth prevalence of the Crouzon syndrome is presented. The fraction of Crouzon syndrome patients in large clinical surveys of all cases of craniosynostosis is calculated and the fractional component obtained is multiplied by the known birth prevalence of craniosynostosis in general. Crouzon syndrome makes up approximately 4.8% of all cases of craniosynostosis. Using a weighted average estimate, birth prevalence was calculated to be 16.5/1 000 000. The results of the indirect method compare favorably with those obtained by the direct method. Nevertheless, because the indirect method is based on a number of assumptions that are easily violated, we cannot recommend its general use except under special circumstances.

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