CLINICAL CHARACTERISTICS PREDICT RESPONSE TO ANTITHYMOCYTE GLOBULIN IN PAROXYSMAL-NOCTURNAL HEMOGLOBINURIA

Seven patients with paroxysmal nocturnal haemoglobinuria (PNH) were tr eated with antithymocyte globulin (ATG). Each patient received ATG (20 mg/kg/d) for 8 d and prednisone to prevent or control serum sickness. Three patients experienced a sustained improvement in at least one pe ripheral blood cytopenia, including one patient who had a complete tri lineage response. Several pretreatment clinical features appeared to b e associated with response to ATG. All responding patients had hypopro liferative features including depressed platelet counts (<30 x 10(9)/l ), and a minor degree of chronic haemolysis as indicated by relatively low reticulocyte counts (<100 x 10(9)/l), lactate dehydrogenase (<100 0 U/l) and total bilirubin (<17 mu mol/l) levels. Responding patients continued to have chronic low-grade haemolysis after their response to immunosuppression that was similar to that observed prior to treatmen t, The non-responding patients had a classic haemolytic form of PNH ch aracterized by elevated reticulocyte counts (>100 x 10(9)/l), lactate dehydrogenase (>2000 U/l) and total bilirubin (>17 mu mol/l) levels. T he impaired haemopoiesis that occurs in hypoproliferative PNH may resp ond to ATG treatment, but the haemolytic component of the disease, and hence the PNH clone, is not altered by immunosuppressive therapy.