**5.7 Rheumatoid arthritis**

DNA sequences from *Pg* have been isolated from the synovial fluid and bloodstream of patients with rheumatoid arthritis (RA). Further to this, the consistently reported relationship between an oral *Pg* infection and RA has encouraged medical clinicians to place more emphasis on the oral health of their patients [71].

#### **Figure 7.**

*The virulence factors of Pg and the systemic illnesses with which they have been associated. (A) Alzheimer's disease, Parkinson's disease, depression, (B) head and neck cancers, (C) atherosclerosis, myocardial infarction, aortic aneurism (D) aspiration pneumonia, (E) non-alcoholic fatty liver disease (NASH) (F) diabetes mellitus (G) rheumatoid arthritis (H) adverse pregnancy outcomes.*

#### **5.8 Adverse pregnancy outcomes**

*Pg* DNA has also been detected in the amniotic fluid, umbilical cord, and placenta of women who encountered pregnancy complications such as preeclampsia and preterm birth [72]. Additionally, results from animal studies suggest that the mechanism involves the direct invasion and damage of the uterine and placental tissue [65].

The adage that correlation does not mean causation, should be considered, and although *Pg* cannot be the sole etiological agent of all the systemic diseases with which it is associated, there is accumulating evidence demonstrating its value as a modifiable risk factor for the prevention, management, and treatment of PD and other systemic diseases (**Figure 7**) [65].
