Background Psoriasis is a prevalent inflammatory skin disease. Psoriasis is a complex illness in which environmental variables acting on individuals with unique genetic predisposition causing immunological dysregulation. Claudins are transmembrane proteins that help to generate tight junctions by binding to the actin cytoskeleton. Claudin 3 in the blood is thought to be a good indicator of intestinal permeability. Objective: The aim of this study was to detect of the alteration of claudin-3 in psoriasis patient and find the correlation between severity and concentration of the claudin-3. Patients and methods: forty psoriatic patients (25males and 15 females) and thirty normal healthy controls (19 men and 11 females) who were age and sex matched to the cases group were included in this study. They were chosen at random from Al Fallujah hospital Dermatology Department outpatient clinic. Result: When compared to the control group, the psoriasis group had substantially greater levels of claudin-3 (mean=2.18 ± 0.16 versus 1.27 ± 0.03; p0.0001). Furthermore, the amount of claudin-3 rose progressively as the severity grade increased (001). There were no significant correlations between claudin-3 levels and gender, dietary status, or family history in the psoriasis group (p>0.05 for each). Conclusion: Claudin-3 levels were considerably greater in psoriasis patients than in healthy controls. PASI levels were shown to be linked to claudin-3 levels.

The index score of psoriasis severity (PASI) cannot always be of value as a marker in non- plaque psoriasis. Alternative biomarkers have been used for the diagnosis and prognosis of the disease. Among these markers are the transmembrane protein Claudin-3 and the Monocyte to High- density lipoprotein cholesterol Ratio (MHR). Objective: The present work was carried on to evaluate the prognostic and diagnostic ability of the two biomarkers for psoriasis, Claudin-3 and MHR, relate them to the PASI score in psoriatic patients, and find the correlation between the two markers. Subjects and methods: forty patients with psoriasis (25 males and 15 females) of 7.3 ±3.7 years disease duration, and 30 healthy control subjects of 19 males and 11 females were enrolled in the study from March to July 2021. The following tests were done for each patient and control subjects: Complete blood count (CBC) by VCS Technology Hemoglobinometry, Claudin-3 by ELISA technique, and serum lipids by enzymatic spectrophotometric methods. Results: Both markers (Claudin-3 and MHR) showed significantly higher values in the patient’s group than their controls in a manner proportional to the severity of the disease. As diagnostic markers, the receiver operating characteristic curve (ROC) analysis for both of them gave acceptable sensitivity and specificity. Conclusion: Claudin-3 and MHR can be used alternatively as adjuvant diagnostic and prognostic markers to PASI score for psoriasis. Keywords: Psoriasis, PASI score, Claudin-3, Monocyte-HDLc ratio.