**5. Periodontal diseases as a manifestation of systemic genetic disorders**

Certain systemic disorders predispose the patient's susceptibility to acquire periodontal disease, which may present clinically in a chronic or an aggressive form. The *involved pathogenesis includes* modifications in the immune, endocrine and connective tissue status of the individual. These changes eventually result in the occurrence of syndromes with periodontal disease either as a primary manifestation or by aggravating a pre-existing condition associated with the presence of local factors. The alterations in the immune system may be noted at cellular and/ or humoral level. Lymphocytes play a pivotal role in driving the immune response, and a defect or absence of one or more lineages may result in fatal conditions like leukaemia or Acquired immune-deficiency syndrome [61]. Neutrophil defects in turn may be of a qualitative (altered chemotaxis and phagocytosis) or quantitative nature (neutropenia, agranulocytosis), and both predispose to rapid and severe periodontal destruction.

A high susceptibilty to develop periodontitis has been associated with conditions such as Down syndrome (trisomy 21), Chediak-Higashi syndrome and Papillon-Lefèvre syndrome. These subjects present with an increased incidence of infections with a plausibility owing to a diminished expression of surface glycoproteins required for bacterial adhesion [62]. Other connective tissue disorders, also induce an elevation to periodontal inflammation mostly linked with plaque and in some cases an overstated response relatively disproportionate to the amount of microbial plaque present.

#### **5.1 Unleashing the underlying mechanism**

Inorder to understand the pathogenesis of Genetic diseases, they have been broadly classified as,

