Aggressive periodontitis with neutropenia caused by MMD2 mutation

Aggressive periodontitis causes rapid periodontal tissue destruction and is a disease that occurs at a young age and runs in the patients family. Here, we revealed a heterozygous A116V missense mutation in the gene encoding monocyte to macrophage differentiation associated 2 (MMD2) protein in a Japanese family with aggressive periodontitis and neutropenia. Analyses of patients peripheral blood revealed a low number of neutrophils but abundant quantity of CD34+ hematopoietic stem and progenitor cells (HSPCs). Moreover, mutant Mmd2 mice showed severe alveolar bone loss and neutropenia. In patients and mutant Mmd2 mice, differentiation of HSPCs into granulocytes was also impeded, and their granulocytes were functionally impaired. Taken together, A116V mutation in MMD2 gene induced mild neutropenia and slightly limited the immune defense response. Our studies suggested that aggressive periodontitis in association with A116V MMD2 mutation constitutes a new immune system defect that belongs to the same spectrum of severe congenital neutropenia.