Heredity of juvenile periodontitis.

A family study was carried out, based on the hypothesis that juvenile periodontitis is inherited in an autosomal recessive mode. Propositi were selected according to standardized criteria. Thirty-one cases with a female/male ratio of 20 to 11 were obtained. Their first-degree relatives were examined radiographically, mostly by orthopantomography. sixty parents, 64 siblings (out of 66) and three children aged 13-16 were traced and examined. Neither parents nor the children showed findings suggestive of juvenile periodontitis, whereas 11 of the 64 siblings were affected. The genetic ratio was first calculated by using an a priori method assuming complete ascertainment. The result, 0.256 +/- 0.061, is close to the theoretical assumption of 0.25. Since the calculation was based on the assumption that juvenile periodontitis is inherited as an autosomal recessive trait, the results were also exposed to an a posteriori analysis assuming a truncate, complete ascertainment. The result, 0.268 +/- 0.062, is again close to the expected ratio for autosomal recessive inheritance. A third method assuming a single, very incomplete ascertainment gave a much lower ratio. It is concluded that the results of the family study are compatible with the hypothesis that juvenile periodontitis is inherited in an autosomal recessive mode.