Treatment of immune-mediated hemolytic anemia in dogs with cyclophosphamide

A review of 60 cases of immune-mediated hemolytic anemia (IMHA) in the dog was performed in order to characterize the disease and to identify potentia l prognostic indicators. Dogs ranged in age from 1 to 13 years, with a mean age of 6.5 years. The 2 most commonly affected breeds were Cocker Spaniels and Labrador Retrievers. Fifty-two of the 60 dogs tested (87%) were autoag glutination positive and spherocytes were present in 45 (75%). Forty-one (8 9%) of 46 patients tested positive for the presence of immunoglobulin on th e red blood cell surface (Coombs assay). The most common clinical signs at presentation were lethargy, weakness, pale mucous membranes, icterus, hemog lobinuria, and anorexia. PCV less than 25% was present in 59 (98%) dogs. At the time of presentation. 35 dogs (58%) had a nonregenerative anemia where as 25 patients (42%) had a regenerative response. Thrombocytopenia was seen in 41 (68%) dogs. Nine of 34 dogs (26%) had a prolonged prothrombin time, 19 of 34 (56%) had a prolonged activated partial thromboplastin clotting ti me, and 12 of 34 (35%) had abnormal fibrinogen concentrations. All dogs rec eived prednisone at immunosuppressive doses (2.2-4.4 mg/kg PO as a single o r divided dose every 24 hours) and cyclophosphamide as primary therapy. For ty-one dogs (63%) received cyclophosphamide at 50 mg/m(2) q24h for 4 days, whereas 9 dogs (15%) received an initial high dose (200 mg/m(2)) followed b y 3 days of a lower dose (50 mg/m(2) q24h). No statistical difference in su rvival times was found for either protocol. Thirteen does were treated with azathioprine in addition to cyclophosphamide and prednisone. The median su rvival time of dogs that received all 3 drugs was 370 days as compared to 9 days for those dogs that were treated with cyclophosphamide and prednisone alone. Thirty-one (52%) dogs died from the disease, 13 (22%) dogs were ali ve, and 15 (25%! dogs were lost to follow-up. The median length of survival for all dogs was 21 days. Eight dogs that were discharged from the hospita l suffered a relapse (PCV < 25%).