Periodontitis in the primary dentition associated with Actinobacillus actinomycetemcomitans infection and leukocyte dysfunction

2 siblings, aged 5 years (girl) and 7 years (boy), with periodontitis in the primary dentition were studied. Actinobacillus actinomycetemcomitans was isolated from the gingival pockets of both children. The titers of IgG antibodies against A. actinomycetemcomitans were elevated, and the polymorphonuclear leukocytes had a decreased capacity to ingest IgG-coated latex particles. Other functions of the polymorphonuclear leukocytes were normal. After antibiotic therapy and for the 7-year-old boy, debridement of the gingival pockets A. actinomycetemcomitans was no longer detectable in the gingival pockets, and the phagocytic capacity of the polymorphonuclear leukocytes was normalized. After 2 1/2 years, A. actinomycetemcomitans was found again in the gingival pockets of the boy, and once more his polymorphonuclear leukocytes had a decreased capacity to ingest IgG-coated latex particles. The antibiotic therapy was repeated and 6 months later, the number of A. actinomycetemcomitans was very low and the phagocytic capacity of the polymorphonuclear leukocytes was back to normal. This case report suggests that A. actinomycetemcomitans may be involved in the etiology of periodontitis in the primary dentition, possibly by triggering a phagocytic dysfunction of polymorphonuclear leukocytes.