A Rare Case of Paroxysmal Nocturnal Hemoglobinuria With Bilateral Renal Vein Thrombosis

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hematopoietic stem cell (HSC) disorder characterized by a partial or complete deficiency of glycosyl-phosphatidylinositol (GPI)-linked membrane proteins, which leads to intravascular hemolysis. The loss of CD55 and CD59, two GPI-anchored proteins on red blood cell surfaces, from mutations in the X-linked phosphatidylinositol glycan class A (PIGA) gene, causes unrestricted proliferation of complement activation. The loss of CD59 especially leads to 'paroxysms' of acute intravascular hemolysis during events of stress. Extravascular hemolysis also occurs without CD55 as the accumulation of C3 on red blood cell surfaces leads to their destruction by the reticuloendothelial system. Diagnosis of PNH relies primarily on clinical presentation and flow cytometry assays used to detect the GPI-anchored proteins, CD55 and CD59; however, fluorescein-labeled proaerolysin variant (FLAER) is seen to have a significant advantage over CD55 and CD59. Typical symptoms of the disorder include fatigue, shortness of breath, hemoglobinuria, abdominal pain and bone marrow failure. Thrombosis also occurs secondary to nitric oxide (NO) deficiency, release of procoagulants, increased tissue factor and reduced fibrinolysis. The classification of PNH is subdivided into three types: classical, PNH with another bone marrow disorder and subclinical PNH. Management of hemolysis, thrombosis and pancytopenia is based on the pathogenesis involved. Inhibition of complement in the form of humanized monoclonal antibody against complement C5 (eculizumab) is seen as an emerging treatment option, while stem cell/bone marrow transplant may also be offered. We present a rare case of PNH with bilateral renal vein thrombosis, who was diagnosed with classical PNH on clinical presentation and flow cytometry. He was initially offered bone marrow transplantation but was lost to follow-up and later presented with bilateral renal vein thrombosis. He was managed conservatively with transfusions and anticoagulation, and was discharged for follow-up on an outpatient basis.

Keywords: cd55 cd59; gpi; paroxysmal nocturnal hemoglobinuria (pnh); piga; renal vein thrombosis.