Lupus anticoagulant-hypoprothrombinemia syndrome (LAHPS) is a rare acquired bleeding disorder secondary to development of antibodies against prothrombin protein, in the presence of antiphospholipid antibodies. We describe the case of a 13-year-old girl who presented with severe menorrhagia and symptomatic anemia. Labs indicated anemia, thrombocytopenia, elevated PT and aPTT, high-titer inhibitor on mixing studies, positive ANA and anti-dsDNA antibodies, along with a triple-positive antiphospholipid antibody panel. Given additional systemic manifestations, systemic lupus erythematosus was diagnosed. High dose steroids and hydroxychloroquine subsequently started. Her clinical course was complicated by femoral deep venous thrombosis and post renal biopsy retroperitoneal hematoma. Further workup revealed low prothrombin level and the diagnosis of lupus anticoagulant hypoprothrombinemia syndrome. In view of suboptimal response to initial immunosuppressive therapy, rituximab was added to her regimen, leading to an improvement in clinical symptoms and resolution of hypoprothrombinemia. She remains recurrence free 5 years from the event. Highlights: Lupus anticoagulant hypoprothrombinemia syndrome (LAHPS) is a rare acquired disorder caused by the formation of prothrombin antibodies in patients with antiphospholipid antibodies. No standard of care exists due to paucity of data; treatment largely relies on supportive transfusions and immunosuppressive therapy. We discuss the case of a 13-year-old girl with LAHPS who was successfully treated with rituximab after proven to be steroid-refractory. LAHPS patients who demonstrate poor response to high-dose corticosteroids can potentially be treated with rituximab with good outcomes. [ABSTRACT FROM AUTHOR]