Lupus anticoagulant hypoprothrombinemia syndrome (LAHPS) is a rare acquired disorder associated with several different conditions but mostly with systemic lupus erythematosus (SLE). LAHPS probably results from the presence of anti-Factor II antibodies, which usually counterbalance the prothrombotic effect of the lupus anticoagulant (LAC). In fact, Factor II deficiency in SLE is invariably associated with the presence of LAC. No consensus exists for the treatment of LAHPS. Corticosteroids, with or without the addition of vitamin K or blood products, have been a successful first-line treatment. Immunoglobulin (IVIG) treatment has been shown to be effective in the setting of acute bleeding. However, in some patients, conservative treatment is not enough to control bleeding, and the addition of immunosuppressive therapy, usually azathioprine, is needed. In our patients, Factor II deficiency reappeared after tapering steroids. Both children achieved normal Factor II levels with cyclophosphamide. This effect was long-lasting, a phenomenon that has not been documented in children prior to this report.