Behçet's disease (BD) is a systemic vasculitis affecting both small and large blood vessels in the venous and arterial systems. It is a multiorgan disease with various manifestations, including mucocutaneous, articular, ocular, gastrointestinal, vascular, and neurological involvements. The aim of present study is to assess pan immune inflammation value (PIN) value in BD in comparison to healthy control ,assess the PIN value in association with demographics and clinical characteristics of Behcet patients and to assess the PIN value in association with disease activity.

Behçet's disease (BD) is a systemic vasculitis affecting both small and large blood vessels in the venous and arterial systems. It is a multiorgan disease with various manifestations, including mucocutaneous, articular, ocular, gastrointestinal, vascular, and neurological involvements. Inflammation of the vascular wall is the primary pathophysiology contributing to thrombosis in BD. Hematological and biochemical values are altered due to systemic inflammation and aberrant immune response. Neutrophils, lymphocytes, and platelets play a significant role in systemic inflammation and thrombosis. In addition to the number and volume of peripheral cells, changes in multiple cell count ratios, such as the platelet-to-lymphocyte ratio (PLR), neutrophil-to-lymphocyte ratio (NLR), and monocyte-to-lymphocyte ratio (MLR), have become important predictors of the diagnosis, disease activity, s and severe organ damage in rheumatologic disorders. pan immune inflammation value (PIV) was first described by Fuca et al and used to evaluate the inflammation. Literature showed that PIV performed better than previous immune-inflammatory biomarkers, such as NLR in colorectal cancer patients. PIV is calculated from four blood cell counts, including neutrophils, platelets, monocytes, and lymphocytes. In some rheumatological diseases such as RA, familial Mediterranean fever, and vasculitis, PIV has been studied.

In clinical practice, hematological and inflammatory laboratory tests are easily accessible and cost-effective. It is important to determine which blood parameter will be more effective in detecting disease activity and monitoring the treatment response in BD. In our study, our aim is to investigate the association of PIN with demographics and clinical characteristics of BD patients and its correlation with disease activity.

Inclusion Criteria:

• Adult BD patients who fulfilling the criteria for the diagnosis by International Team for the Revision of the International Criteria for Bechet's Disease .
• Accept to participate in the current study.

Exclusion Criteria:

• Individuals with other autoimmune diseases.
• Patients unwilling to participate in the study.
• Patients less than 18 years old.
• Patients with malignancy or infections.
• Pregnancy and lactation

Adult BD patients who fulfilling the criteria for the diagnosis by International Team for the Revision of the International Criteria for Bechet's Disease attending Rheumatology, Rehabilitation and Physical Medicine Department, Assiut University Hospitals.