Transient thrombocytopenia in a cat following G‐CSF treatment

A 4‐year‐old, castrated male, Russian blue cat with idiopathic epilepsy was diagnosed with neutropenia. The neutropenia was classified as idiopathic after blood tests and abdominal imaging did not reveal an infectious, inflammatory or neoplastic aetiology. As a treatment trial for idiopathic neutropenia, the cat was administered granulocyte colony‐stimulating factor by subcutaneous injection once daily for 3 days. Two weeks after completion of granulocyte colony‐stimulating factor therapy, the cat developed severe thrombocytopenia, with the granulocyte colony‐stimulating factor therapy considered to be the most likely cause. No treatment was initiated, and the thrombocytopenia had resolved spontaneously by 2 weeks after diagnosis. This is the first reported case of transient severe thrombocytopenia in a cat following granulocyte colony‐stimulating factor treatment.