Systemic Inflammation Marker Alterations in Severe Alopecia Areata Patients Treated with Janus Kinase Inhibitors

<b>Background/Objectives</b>: Alopecia areata is an autoimmune disorder characterized by nonscarring hair loss and systemic immune dysregulation. Hematological indices such as neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), mean platelet volume (MPV), systemic immune-inflammation index (SII), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) have been associated with inflammatory activity in dermatologic diseases. This study aimed to compare systemic inflammatory markers among patients with severe and mild alopecia areata and healthy controls, and to explore longitudinal changes in these markers in patients with severe disease who achieved clinical improvement following Janus kinase (JAK) inhibitor therapy. <b>Methods</b>: This retrospective cohort study included 129 participants: 43 patients with severe alopecia areata (SALT ≥ 50) treated with JAK inhibitors who achieved documented clinical improvement, 43 patients with mild disease (SALT ≤ 20), and 43 age- and sex-matched healthy controls. Hematological inflammatory markers, including red cell distribution width (RDW), MPV, MLR, NLR, PLR, SII, ESR, and CRP, were compared across groups. In patients with severe disease, longitudinal changes were assessed at baseline, three months after treatment initiation, and at the time of documented clinical improvement. <b>Results</b>: MLR, NLR, PLR, SII, and ESR levels were significantly higher in the severe group compared with mild cases and controls, while RDW, MPV, and CRP showed no significant differences. Among patients with severe alopecia areata who achieved clinical improvement following JAK inhibitor therapy, NLR and SII decreased significantly over time. MLR, PLR, and CRP also showed reductions during follow-up, while ESR and RDW remained unchanged. <b>Conclusions</b>: Systemic inflammatory markers are elevated in severe alopecia areata compared with mild disease and healthy controls. In patients who achieved clinical improvement with JAK inhibitor therapy, several inflammatory indices demonstrated longitudinal changes. These findings are exploratory and suggest an association between systemic inflammation, disease severity, and clinical improvement rather than definitive predictive biomarkers.