Autoimmune hemolytic anemia (AIHA) is a rare disease with an incidence of 0.2 per 1,000,000 individuals under 20 years of age. Patients with AIHA have a higher propensity for thrombotic events and other autoimmune disorders. Studies demonstrate that 11-20% of that population may develop thromboembolic events during anemic episodes.

Male, 71 years old, diagnosed with primary AIHA in August/2023 after ruling out secondary causes. In December/2023, he presented spontaneous pulmonary thromboembolism (PTE) as the first thrombotic event. Anticoagulation was started with rivaroxaban for 6 months until July/2024, when it was discontinued due to gastrointestinal (GI) bleeding without identifiable lesions on colonoscopy. The patient has maintained AIHA treatment with prednisone since diagnosis. In February/2025, after 6 months without anticoagulation, he complained of exertional dyspnea and fatigue for 3 months, presenting markedly elevated D-dimer (5,873 ng/ml; NV < 500 ng/ml). Due to clinical suspicion of PTE, he was referred to the emergency department, where full anticoagulation with enoxaparin was initiated. Chest CT angiography confirmed filling defect at pulmonary artery bifurcation. During hospitalization, there was progressive hemoglobin (Hb) decline requiring increased corticotherapy from 15 mg/day to 100 mg/day. On the 10th day, pulsotherapy was performed as a result of his low level of Hb (5.8 g/dl) despite optimized medications. After 2 days, he developed hematochezia episodes maintained even after enoxaparin discontinuation. On the 17th day, due to pulse therapy-refractory AIHA, rituximab 375 mg/SC was prescribed, prednisone returned to 100 mg/day, and an inferior vena cava filter was placed. After 26 days, Hb stabilized at 9.5 g/dl, colonoscopy showed no abnormalities, and he was discharged with prednisone 60 mg/day and apixaban. During outpatient follow-up, he remains stable and without new bleeding episodes, with Hb at 12.3 g/dl. DISCUSSÃO: Several mechanisms justify thrombotic predisposition in AIHA: erythrocyte membrane alteration by autoantibodies with coagulation enzymatic complex formation; red blood cell surface destruction; free Hb from hemolysis increasing adhesion molecule expression; pro-inflammatory effects of free heme, among others. Additionally, glucocorticoid therapy also contributes to prothrombotic state in these patients. Anticoagulant prophylaxis, although not recommended by guidelines and lacking randomized clinical trials for validation, has proven useful in studies with hospitalized patients. In this case, the patient had a thrombosis history, but anticoagulation discontinuation became necessary due to GI bleeding without apparent cause on colonoscopy, thus attributed to rivaroxaban. Meta-analyses indicate greater association of rivaroxaban with GI bleeding compared to apixaban, which has a more favorable safety profile, justifying the medication switch at discharge.

Despite being rare, AIHA is a severe disease with considerable morbimortality, deserving attention for early diagnosis and treatment. In the future, randomized clinical trials should be proposed to validate the benefit of thrombotic event prophylaxis in this patient profile, ensuring better quality of life and reduced morbimortality.