Paroxysmal nocturnal hemoglobinuria (PNH) is a disease caused by a defect in the bone marrow stem cells causing a red cell membrane abnormality. It is characterised by red cell haemolysis (breakdown) resulting in the release of haemoglobin into the urine imparting a dark colour to it. The disease may present as a haemolytic anaemia, thrombotic episodes in large veins or bone marrow suppression causing pancytopenia (i.e. anaemia, decrease in white cells [leukopenia] and reduced platelets [thrombocytopenia]). The condition is insidiousl and follows a chronic course with morbidity depending on the degree of haemolysis, thrombophilia and bone marrow failure.
Being a defect of the marrow stem cell, the ideal curative treatment would be a stem cell transplant but this is not done routinely due to lack of a histocompatible donor and the significant morbidity and mortality associated with the procedure. BMT is reserved for patients with severe aplastic anaemia or those in leukemic transformation. Instead, antithymocyte globulin (ATG) has been used to treat aplastic anaemia.
The current therapy is symptomatic. Anaemia is treated by folic acid & iron supplements along with leukocyte-depleted packed cell transfusions. High dose glucocorticoids have been used too but these have serious long-term complications. Red cell production (erythropoiesis) can be stimulated using the hormone erythropoietin, which has largely replaced the use of androgens. Thrombosis is treated conventionally by heparin and oral anticoagulants. A new drug, eculizumab, has recently been shown to be highly effective in reducing intravascular haemolysis and clinical trials are on.
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