Immune-mediated hemolytic anemia (IMHA) is a condition less commonly seen in cats than in dogs. The condition develops due to antibody-mediated erythrocyte (red blood cell) destruction as either a primary (idiopathic) or secondarily to a stimulus that triggers the destruction, such as feline leukemia virus (FeLV), Mycoplasma hemofelis, drugs or neoplasia.
Primary IMHA is usually associated with a reticulocytosis, though evidence of regeneration is sometimes not found due to the destruction of erythrocyte precursors. The two conditions where this is noted are pure red cell aplasia (PRCA) and non-regenerative immune-mediated hemolytic anemia (NRIMHA). PRCA is characterized by bone marrow erythroid aplasia or hypoplasia. NRIMHA is associated with bone marrow erythroid hyperplasia and/or erythroid maturation arrest.
The authors in this retrospective study aimed to describe the clinical syndrome, treatment and outcome (remission and survival) of these two disorders and compare the outcome between the two. Over a period of 5 years, fifteen cats met the inclusion criteria: seven with PRCA and eight with NRIMHA. Twelve of the fifteen cats were younger than 3 years of age and thirteen of the fifteen had severe anemia (Hct < 15%). The majority of the cats had FeLV provirus PCR performed on bone marrow samples and hemoplasma PCR performed and all were negative for both.
In regards to treatment, a whole blood transfusion with or without Oxyglobin was necessary in almost all of the cats. Eleven of fifteen cases achieved remission 12-42 days after starting immunosuppressive treatment. The treatment protocols associated with remission were glucocorticoids, glucocorticoids and chlorambucil, glucocorticoids and cyclosporine and cyclosporine alone. Relapse was observed in three of eleven cats. The outcome (remission and survival) was not different between PCRA and NRIMHA.
The authors conclude that both conditions are uncommon causes of anemia in predominantly young cats. Prognosis is reasonable though mortality rate is around 27%. Most cats require one blood transfusion. Remission can take up to at least 6 weeks before it is observed. Following remission, immunosuppressive treatments should be gradually withdrawn using close monitoring in case of relapse. Some cases may require long-term treatment. (VLT)