Psoriasis is a chronic inflammatory disease with a multi-factorial etiology which affects the epidermis and dermis. It affects around 1-3% of the general population and its most frequent form is plaque psoriasis (around 80-90% of the overall psoriasis cases). Psoriasis severity and extension are usually measured through 2 scores: Psoriasis Area Severity Index (PASI) and Body Surface Area (BSA). Periodontitis is a chronic inflammatory disease mediated by the biofilm and with a multi-factorial etiology. Its manifestation entails the destruction of the periodontal tissues surrounding the teeth; the final stage of disease is characterised by tooth loss. Periodontitis severity and extension are usually evaluated through surrogate variables such as: BoP (Bleeding on Probing), PPD (Probing Pocket Depth) e REC (Recession). Both diseases present overlapping genetic and pathophysiologic features, as well as common risk factors (e.g. genetic polymorphisms, smoking habit, obesity, diabetes etc.).

miRNAs are small non-coding molecules involved in the regulation of various biologic processes thanks to their interaction with mRNAs. Active inflammatory processes either in the oral cavity or at a systemic level tend to alter the concentration of salivary miRNAs. No study so far has ever profiled the levels of specific salivary miRNAs in patients with psoriasis and periodontitis.

Some case-control studies highlighted a higher prevalence of periodontitis in patients with psoriasis when compared to healthy controls. Nonetheless, epidemiological data regarding periodontitis prevalence in patients with psoriasis are lacking; moreover, few data are available regarding the relationship between the severity of psoriasis and the severity of periodontitis, together with the effect of common risk factors (e.g. diet, obesity, physical activity, sleep quality etc.).

Inclusion Criteria:

• Age between 18 and 70 years old
• Diagnosis of plaque psoriasis
• Ability and willingness to give informed consent

Exclusion Criteria:

• Inability of unwillingness to give informed consent
• Pregnancy or lactation

All patients affected by Plaque Psoriasis and meeting the inclusion criteria will be screened for the inclusion in the present study.