Unusual granulation of neutrophils from Siamese cats and possible link with granulation in Birman cats

Unusual granulation of neutrophils from Siamese cats and possible link with granulation in Birman cats
Peer reviewed


Blood samples were received for routine haematological laboratory examination from two elderly Siamese cats. The cats showed mild non-specific signs of illness, and the most significant haematological finding in a peripheral blood smear was of red/azurophilic granules resembling toxic granulation, or the persistence of the primary granules seen within pro-granulocytes, within the majority of neutrophils. Basophils also had large dark blue intracytoplasmic granules. These granules persisted within the neutrophils after treatment and apparent recovery. Similar granules have been very rarely reported but have been noted within neutrophils from three Siamese cats and one Himalayan cat. Morphologically, using routine Romanovsky stains, these granules resembled those seen within the neutrophils of Birman cats affected with an inherited autosomal recessive anomaly. In Birman cats, this abnormal granulation is not associated with any clinical disease.
Toluidine blue stains on blood smears from the two Siamese cats were negative, and ruled out inherited mucopolysaccharidosis Types VI and VII that may cause similar granulation. Siamese and Birman cats arose from South East Asia, and as Siamese cats were used to re-establish the Birman breed after the second World War inbreeding may have produced a founder effect whereby one of the cats used, either Siamese or a surviving Birman, may have carried this gene, resulting in the larger numbers of Birman than Siamese cats showing this anomaly. Likewise, Himalayan cats were developed from Siamese and Persian cats and the Siamese breed may have been the origin of the anomaly in that breed of cat. Electron microscopy, special stains, bone marrow aspirates and gene studies to compare cells from affected individuals of both breeds may help to establish if this is the same anomaly.

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