We had the opportunity to study a family with one of the most destructive forms of periodontal disease known, the Papillon-Lefèvre syndrome. The parents had no consanguinity and were not affected, and were therefore to be considered carriers of the disease. 2 sisters, the eldest and youngest, showed periodontal breakdown and hyperkeratotic skin lesions, but their deciduous dentition was not affected. 2 brothers had skin lesions only and another brother and sister were healthy. Furthermore, 2 babies died at birth one after a 9-month pregnancy and the other after a 6-month pregnancy, and the mother also suffered 3 miscarriages. For 4 years, we studied the family: in the case of both sisters, mechanical periodontal treatment and antibiotics were unable to control the disease. In the chromosomic study of the 2 sisters affected, the GTG banding technique found no trace of anomalies in the cells analyzed, whose chromosomic formation was 46,XX. Before treatment, the chemotaxis of the PMN, the phagocytosis of opsonized Staphylococcus aureus, and production of superoxide radicals by PMN was significantly impaired in both sisters. Despite scaling and root planing, the periodontal lesions still progressed, but the PMN functions evaluated were now normal in both sisters. An orally asymptomatic but dermatologically affected brother showed no significant defect in the phagocytic activity and the production of superoxide radicals.