Granulation anomaly

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A pair of neutrophils in the blood of a Birman cat with the hereditary granulation anomaly. Notice the fine, reddish-purple, cytoplasmic granules (Wright's stain)

Granulation anomaly is an autosomal recessive blood disorder of cats, reported most frequently in Birman cats[1].

Unlike Pelger-Huet Anomaly which is charcterised by agranulation of leukocytes, this disease shows elevated numbers of granulated neutrophils.

A large survey of Birman cats in Canada found that 36 of 78 Birman cats (46%) examined had the neutrophil granulation anomaly. The condition was inherited in an autosomal recessive manner, indicating that both parents must provide a gene to produce the anomaly and that this condition equally affects both males and females[2].

There are no specific clinical signs in affected cats. This hereditary anomaly of neutrophil granulation usually is a serendipitous finding during a routine complete blood cell count[3].

Diagnosis is usually incidental during routine blood testing. On a Romanowsky (Wright, Giemsa, Leishmann, or Diff-Quik) stained peripheral blood smear, neutrophils contain small, cytoplasmic, reddish-purple granules. Ultrastructural studies have indicated that these granules are of normal size. Furthermore, the granules fail to stain with Alcian blue or toluidine blue dyes, indicating that the granules do not contain mucopolysaccharide that is typical of certain hereditary storage diseases (e.g. mucopolysaccharidosis types VI and VII)[1].

In vitro studies have demonstrated that neutrophils from affected Birman cats exhibit bactericidal activity against Escherichia coli that is comparable to that of neutrophils from healthy control cats[4].

A differential diagnosis would include toxic granulation in response to infection or severe inflammation, Pelger-Huet Anomaly, Mucopolysaccharidosis (types VI and VII), GM2-gangliosidosis and Chediak-Higashi syndrome.


  1. Latimer KS, Prasse KW (2003) Leukocytes. In: Latimer KS, Mahaffey EA, Prasse KW: Duncan and Prasse's Veterinary Laboratory Medicine: Clinical Pathology, 4th ed. Iowa State Press, Ames, pp:46-79
  2. Hirsch VM & Cunningham TA (1984) Hereditary anomaly of neutrophil granulation in Birman cats. Am J Vet Res 45(10):2170-2174
  3. Harvey JW (2001) Atlas of Veterinary Hematology: Blood and Bone Marrow of Domestic Animals. W.B Saunders Co., Philadelphia, p:54
  4. Alroy, J et al (1989) Morphology of leukocytes from cats affected with alpha-mannosidosis and mucopolysaccharidosis VI (MPS VI). Vet Pathol 26:294-302