ABSTRACT

Acquired hemophilia A is a rare condition characterized by de novo development of a coagulation factor VIII inhibitor. Inhibition of factor VIII activity results in increased susceptibility to bleeding events, most frequently mucosal or soft tissue bleeding. We report two cases of acquired hemophilia A in previously healthy pediatric patients. Notably, both patients presented with hemarthrosis as the sentinel bleeding event. In both cases, administration of immunosuppressive therapy was associated with inhibitor loss and patient cure. These cases emphasize the importance of considering acquired hemophilia A in pediatric patients presenting with acute onset hemarthrosis.

INTRODUCTION

Acquired hemophilia A (AHA) is a rare bleeding disorder characterized by loss of coagulation FVIII (FVIII) activity with an estimated incidence of 0.6 - 1.48 patients per million per year1–4. AHA predominantly affects elderly populations with a median age at diagnosis of 64 - 78 years-old; it is extremely rare in pediatric populations5. Approximately 50% of cases are idiopathic, but an association with malignancy and autoimmune disease has been suggested5–10. Typical presenting symptoms include subcutaneous bleeding in 80% of patients, as well as bleeding into muscles/soft tissues and from mucus membranes. However, hemarthrosis is uncommon, in contrast to joint bleeding frequently observed in hereditary hemophilia A1,5,11. Little is known about AHA in pediatric patients due to the exceedingly low incidence of AHA in younger demographics. We present two cases of AHA in previously healthy pediatric patients who presented with hemarthrosis.

RESULTS

Case 1

The first patient was a previously healthy 4 year-old male who presented to hematology clinic with right ankle hemarthrosis and increased bruising. He had no prior history of easy bleeding or bruising and a negative family history for bleeding disorders. There was a possible history of a viral infection several weeks prior to presentation. On presentation, laboratory evaluation demonstrated severe FVIII deficiency (<1%) as well as a FVIII inhibitor (5.8 Bethesda Units, B.U.; Fig. 1). He was initially treated with intravenous activated recombinant factor VII (rFVIIa) with improvement in his ankle bleed and bruising. One week later, he developed signs concerning for ongoing bleeding. He was treated with rFVIIa and started on prednisone 1mg/kg/dose twice daily.
Marked improvement was noted at follow-up four weeks after initiating steroid treatment. Prednisone was decreased for a two-week taper. During the taper, he developed recurrent swelling and pain in his ankle related to overuse and received rFVIIa with improvement of pain and swelling. At the time, he was noted to have a factor VIII activity of 9% and a FVIII inhibitor of 2.7 B.U (Figure 1). He had another incident concerning for a distal phalangeal joint bleed within several days of discontinuing prednisone and was treated with two doses of rFVIIa. FVIII activity was noted to have decreased to 1.7% and FVIII inhibitor level increased to 4.3 BU. Given the recurrent bleeding, he was treated with intravenous immunoglobulin (IVIG, 1g/kg) every two weeks for a total of five doses. Improvement of joint pain and swelling was noted following the first IVIG dose. By the fourth IVIG dose, the patient was clinically well, without active bleeding, and his FVIII activity was 15.7%. At six-week follow-up, lab values showed FVIII activity 73% and a FVIII inhibitor 0 BU.