An inherited thrombocytopenia occurs in the condition of Cyclic Hematopoiesis of Gray Collies . This is an autosomal recessive disorder in man and gray collie dogs characterized by cyclic fluctuations in the number of circulating neutrophils, reticulocytes, and platelets. The peripheral cytopenias are the result of a defect in hematopoietic stem cells. The neutropenic and thrombocytopenic episodes occur approximately every 12 days.
Mortality is high in affected puppies and most die of infection before six months of age.
The hematopoietic defect can be corrected by bone marrow transplantation. There are certain dog breeds, such as Cavalier King Charles Spaniels and Greyhounds, which have platelet counts lower than the reference interval. In these breeds, a slightly low platelet count is an expected finding and should not be regarded as pathological. These are larger than the upper threshold of the window for counting platelets in some electronic analyzers, therefore they are excluded from the automated platelet count obtained from that analyzer. This results in a pseudothrombocytopenia.