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rFVIIa and obstructive hydronephrosis

To the Editor: Recombinant Factor VIIa (rFVIIa) has been a useful treatment for hemophilia patients with inhibitors. We present two episodes of obstructive hydronephrosis associated with high dose rFVIIa in a 12-year-old boy (weight 51 kg) with severe factor VIII deficiency and an inhibitor (40 BU). The first episode occurred in the left kidney after rFVIIa (14.4 mg, then 9.6 mg, then 4.8 mg) was given at home for hemarthrosis. Gross hematuria and left flank pain ensued, severe enough to require hospitalization and narcotics for symptom control. Computerized tomography (CT) revealed a non-calcified mass, consistent with hematoma, within the left renal pelvis causing hydronephrosis. Right sidewas clear.With vigorous hydration, clots were passed and the hematuria resolved. Eightmonths later, a target hemarthosiswas treated at homewith rFVIIa at increased dose (24mg then 19.2mg). Gross hematuria and right flank pain began. CT revealed a mass in the right renal pelvis with obstruction and hydronephrosis. Left side was clear. Vigorous hydration helped in resolving the mass and passing clots. Five months later, a CT scan revealed that both kidneys and collecting systems were normal. Subsequent doses of rFVIIa at more conventional doses have not resulted in further problems. This patient had no previous history of hematuria, renal stones, or pertinent trauma. Maximum BUN was 16 mg/dl, baseline was 12 mg/dl. He has congenital severe factor VIII deficiency with a genetic inversion. By age 1, he had an inhibitor. He had a prolonged trial of immune tolerance, but abandoned this at age 5. He uses central venous catheters. His first exposure to rFVIIa was in 1999. He had a previous radionuclide synovectomy of the right knee. Vascular imaging in 2004 was consistent with a left internal jugular vein and left subclavian vein thrombosis. The patient requires a wheelchair. Both episodes occurred within months of a previous febrile illness. Three months before the first episode, the patient developed S. marcesens bacteremia, treated with intravenous antibiotics. Because of an increased frequency of bleeding, a trial of daily FEIBA had been started, with some success. The central line was eventually removed, and daily FEIBA had been stopped 2 weeks before the first episode. Two months before the second episode, he was treated with empiric antibiotics for a fever, but blood cultures were negative. Activated protein C resistance, prothrombin alleles (G21210), fibrinogen, antithrombin III, protein C, protein S, and homocysteine levels were normal; anticardiolipin antibodies were negative. Several factors might have caused a predisposition to these episodes, including the proximal history of fever and antibiotic therapy, the patient’s sedentary routine, and the high doses of rFVII. We speculate that he had renal bleeding into the urinary collecting system that formed an obstructive mass, rather than nephrotoxicity. Thromboembolic events have been reported with rFVIIa [1].