Immune mediated hemolytic anemia (IMHA or AIHA) may be primary immune-mediated or secondary. In primary IMHA, the cause is not known and there may be genetic influences in certain breeds of dogs, eg Cocker spaniels, Poodles, Old English Sheepdogs.
Secondary IMHA may be triggered by neoplasia, infections, auto-immune diseases, or drug-induced. There may be an increased incidence following vaccination, but this is unproven.
The timecourse for the acute form is 1-4 days, and days to weeks for the chronic form.
In acute cases, the dog may present with severe anemia, jaundice, hemoglobinuria, and organ failure (especially liver) due to hypoxia. There may be severe dyspnea due to pulmonary thromboembolism and spontaneous bleeding due to disseminated intravascular coagulation.
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