To evaluate the inheritance mode of aggressive periodontitis in a collection of families with a similar geographic origin.

Segregation analysis was performed in pedigree data from 74 families by the use of the SEGREG program of SAGE v.5.4.2. Homogeneous no transmission, homogeneous Mendelian transmission, homogeneous general transmission, semigeneral transmission and heterogeneous general transmission models were tested assuming the prevalence of aggressive periodontitis as 1% and no deviations from Hardy-Weinberg equilibrium. The parameters of the model were estimated by the method of maximum likelihood, which provides the overall ln (likelihood), −2ln and the AIC (Akaike’s score) for each model. The likelihood ratio test (LRT) was used to compare each model against a fully general model (p>0,05).

The most parsimonious mode of inheritance was the semigeneral transmission model which allows the heterozygote transmission probability to vary.

This result provides strong support for the hypothesis that genetic factors play a role in aggressive periodontitis and that a few loci, each with relatively small effects, contribute to aggressive periodontitis, with or without interaction with environmental factors.

Clinical Relevance

Understanding the mode of inheritance of aggressive periodontitis can better guide future molecular studies aiming to identify contributing genetic factors to the condition.

Our results provide strong support for the hypothesis that genetic factors play a role in aggressive periodontitis, under a model of variable heterozygote transmission.

Family-based designs provide the opportunity to study variation in the phenotype and provide evidence that justifies future family-based genetic analysis. From these approaches comes the possibility to localize disease loci through linkage analysis. The identification of the genetic variation leading to aggressive periodontitis can improve individual risk assessments of this condition in the future.