Serum levels of tumour necrosis factor (TNF-α) and interleukin-17 (IL-17) in patients with nail psoriasis: A cross-sectional study

Psoriasis is a common chronic inflammatory disorder affecting all aspects of a patient’s life. Nail involvement is frequent, but little is known about its associated inflammatory biomarker profile, including similarities or differences from cutaneous disease. We conducted this cross-sectional study to evaluate serum levels of inflammatory cytokines [tumour necrosis factor-alpha (TNF-α) and interleukin -17 (IL-17)] in patients with nail psoriasis and compared these to psoriasis patients without nail involvement, as well as in non-psoriatic healthy controls. Adult psoriasis patients with (Group I, n = 30) and without nail involvement (Group-II, n = 30) were sequentially recruited. In addition, non-psoriatic healthy controls (Group-III, n = 20) were recruited. The nail disease severity by NAPSI score was determined for patients in Group I. Cutaneous disease severity (by PASI score) and presence of psoriatic arthritis (through CASPAR criteria) were evaluated for patients in Groups I and II. Serum levels of TNF-α, IL-17, erythrocyte sedimentation rate (ESR), rheumatoid factor (RA factor), and anti-cyclic citrullinated peptide antibody (Anti-CCP) were evaluated for all three groups. The median age was significantly higher for Group I as compared to Group II patients (41 ± 12.6 years vs 30 ± 12.4 years, p = 0.017). Group I patients also had higher median PASI score than Group II patients, although the difference was not statistically significant (10 ± 11.41 vs 6.50 ± 5.46, p = 0.275). The mean serum IL-17 levels were significantly higher for Group-I (113.39 ± 251.30 pg/mL) than Group II (27.91 ± 18.22 pg/mL, p = 0.002) and Group III (25.67 ± 12.08 pg/mL, p = 0.005). A weak positive correlation was found between NAPSI and serum IL-17 levels (Spearman’s Rho = 0.355) though not statistically significant (p = 0.054). Correlation between serum IL-17 and PASI was poor for Group-I patients (Spearman’s Rho = 0.13, p = 0.944) and strongly negative for Group-II patients (Spearman’s Rho = −0.368, statistically significant with p = 0.045). The mean serum levels of TNF-α were below the detection threshold of the assay kit, hence no meaningful comparison could be made. A small sample size and low sensitivity of TNF-α assay kit. Our study showed that nail psoriasis could be independently associated with an elevation of IL-17. This can help choose appropriate drugs and estimate drug response in patients with nail psoriasis.