[A long-lasting idiopathic factor V inhibitor].

A rare case of a long-standing idiopathic acquired blood coagulation factor V (FV) inhibitor is reported. A 78 year-old male was admitted complaining of hematuria and tarry stools of two weeks' duration. He was noted to have a prolonged prothrombin time and activated partial thromboplastin time. A mixing study suggested the existence of an inhibitor and the activity of FV was less than 1%. Western blot analysis revealed the presence of anti-FV antibodies in the patient's serum. Because of significant bleeding tendencies, the patient received fresh-frozen plasma, platelet transfusions and methylprednisolone. His PT, APTT and FV activity were partially corrected although the disease was exacerbated when the steroid dose was tapered off. The patient was then treated with low dose cyclophosphamide. The majority of the cases with acquired FV inhibitor occur spontaneously in older patients but this condition may be associated with a surgical procedure, administration of antibiotics, tuberculosis or malignant diseases; some of them are, however, idiopathic. No underlying disease was detected in our present patient. The inhibitor disappears within 10 weeks in most patients and the prolonged presence of an idiopathic FV inhibitor is rare.