Excellent article, very well done. The major thrust of the article is to identify a pattern, if possible, for the genetic transmission of juvenile periodontitis. The importance of this circa 1980, was that if it could be demonstrated that there was a genetic linkage to juvenile periodontitis, then it could be considered a separate disease entity. The hypothesis for this experiment was that juvenile periodontitis is an autosomal recessive disease entity. 31 cases of juvenile periodontitis were obtained, with a female to male ratio of 20 to 11. Their first degree relatives were examined radiographically, mostly by orthopantomographs. 60 parents, 64 siblings, and 3 children of the 31 subjects were examined. Neither parents, nor children, showed findings suggestive of juvenile periodontitis. (Note: only children and siblings 13 or older were included due to the age of onset of this disease.) 11 of the 64 siblings were affected.
Results: the genetic ratio was calculated in three different ways and found to be 0.256 +/- 0.061 (1 SD unit) in the first method and 0.268 +/- 0.062 in the second method. The third method gave a much lower ratio of 0.169 +/- 0.47. These were very close to the theoretical ratio of 1 out of 4 children (0.25 ratio) to have juvenile periodontitis passed to them by their parents if the disease is autosomal recessive. (the siblings would have to be homozygous for the recessive gene, the parents would have to be heterozygous since they did not have juvenile periodontitis, therefore 1 out of 4)) The sex ratio of the affected siblings was 7:4 female to male. The author concluded that there is no sex linked mode of inheritance and that the 20:11 ratio of subjects was because of chance or the self-selection of women having dental visits more often. The 7:4 ratio in siblings was attributed to small numbers of affected siblings. The author also concluded that autosomal dominant inheritance was not possible and that the results were compatible with an autosomal recessive mode of genetic transmission.
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