Hematologic Involvement in Systemic Lupus Erythematosus: Clinical Features and Prognostic Implications in a Hematology-Referred Cohort

<b>Background/Objectives:</b> Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disease frequently complicated by hematologic abnormalities, which may reflect disease activity or treatment effects. To characterize the clinical, laboratory, and immunological features of adult SLE patients referred to hematology during routine rheumatology follow-up. <b>Methods:</b> We retrospectively analyzed 84 adult SLE patients who fulfilled the 2012 SLICC or 2019 EULAR/ACR criteria and were referred to hematology during follow-up. Clinical, laboratory, and immunological data were collected. Associations between hematologic manifestations, organ involvement, autoantibodies, and complement levels were evaluated. <b>Results:</b> The cohort included 92.6% females with a median age of 46 (IQR 36-62). Hematologic abnormalities commonly appeared within three years of disease onset. Lymphadenopathy was more frequent in patients with cutaneous vasculitis and lupus nephritis (<i>p</i> = 0.046 and <i>p</i> = 0.045). Splenomegaly was associated with serositis, anti-β2 glycoprotein I IgG, and lupus anticoagulant (LA) positivity; anti-β2GPI IgG independently predicted splenomegaly (OR 26.02, <i>p</i> = 0.006). Low C4 was associated with increased autoimmune hemolytic anemia risk (OR 5.88, <i>p</i> = 0.009), while low C3 was linked to lupus nephritis (<i>p</i> = 0.017). Antiphospholipid antibodies were significantly associated with venous thrombosis, with anti-cardiolipin IgG as an independent predictor (OR 7.43, <i>p</i> = 0.007). Stroke history, anti-histone antibodies, and higher steroid doses were associated with mortality. Remission was linked to fewer comorbidities (<i>p</i> = 0.008). <b>Conclusions:</b> Hematologic complications in SLE arise early and carry prognostic significance, with splenomegaly associated with lupus anticoagulant and anti-β2GPI IgG, and mortality linked to anti-histone antibodies.