Page 1401 - Small Animal Internal Medicine, 6th Edition

CHAPTER 85 Leukopenia and Leukocytosis 1373

BOX 85.1
VetBooks.ir Causes of Neutropenia in Cats and Dogs

Decreased or Ineffective Production of Cells in the
Anaplasmosis (D, C)
Proliferating Pool Ehrlichiosis (D, C)
Myelophthisis (neoplastic infiltration of the bone marrow) Toxoplasmosis (D, C)
Myeloproliferative disorders (D, C) Early canine distemper virus infection (D)
Lymphoproliferative disorders (D, C) Early canine hepatitis virus infection (D)
Systemic mast cell disease (D, C) Other
Malignant histiocytosis (D, C?)
Myelofibrosis (D, C) Idiopathic bone marrow hypoplasia-aplasia (D, C)
Cyclic neutropenia of gray Collies (D)
Drug-induced neutropenia Trapped neutrophil syndrome of Border Collies (D)
Anticancer and immunosuppressive agents (C, D) Acquired cyclic neutropenia (D, C)
Chloramphenicol (C) Steroid-responsive neutropenia (D, C)
Griseofulvin (C) Sequestration of Neutrophils in the Marginating Pool
Sulfa-trimethoprim (D, C)
Estrogen (D) Endotoxic shock (D, C)
Phenylbutazone (D) Anaphylactic shock (D, C)
Phenobarbital (D) Anesthesia (D?, C?)
Other Sudden, Excessive Tissue Demand, Destruction, or
Toxins Consumption
Infectious diseases
Industrial chemical compounds (inorganic solvents,
benzene) (D, C) Peracute, overwhelming bacterial infection (e.g.,
Fusarium sporotrichiella toxin (C) peritonitis, aspiration pneumonia, salmonellosis,
metritis, pyothorax) (D, C)
Infectious diseases Viral infection (e.g., canine distemper or hepatitis,
Parvovirus infection (D, C) preclinical stage) (D)
Retrovirus infection (feline leukemia virus, feline • Drug-induced disorders (D, C) (see above)
immunodeficiency virus) (C) • Immune-mediated disorders (D, C)
Myelodysplastic or preleukemic syndromes (C) • Paraneoplastic (D)
Cyclic neutropenia (C) • “Hypersplenism” (D?)
Histoplasmosis (D, C)

Note: Entries in boldface are common causes; entries in italics are relatively common causes; entries in regular typeface are uncommon
causes.
C, Cat; D, dog; ?, poorly documented.

the increased margination or destruction of circulating neu- gene (Mizukami et al., 2012). Steroid-responsive (immune-
trophils (Box 85.1). Neutropenia is relatively common in cats mediated) neutropenia is relatively common in dogs and
and dogs. The clinician should keep in mind, however, that cats. Recently, Devine et al. reviewed the records of 35 dogs
normal cats may have neutrophil counts of 1800 to 2300/µL; with this condition (Devine et al., 2017). The most common
this reference range is also true for Greyhounds and some of clinical signs were lethargy/anorexia (63%), pyrexia (46%),
the other sighthounds. vomiting/diarrhea (43%), pain/lameness (34%), and lymph-
In dogs and cats evaluated in a teaching hospital (Brown adenopathy (17%); 11% of the dogs were asymptomatic
and Rogers, 2001), infectious diseases (feline leukemia virus, (Devine et al., 2017). Bone marrow cytologic evaluation
feline immunodeficiency virus, parvovirus) were the most revealed myeloid hyperplasia in 66% and myeloid hypopla-
common comorbid conditions, accounting for almost 52% sia in 29% of the dogs; 20% of the samples had a maturation
of the cases of neutropenia. Sepsis or endotoxemia accounted arrest. Most dogs (97%) had a rapid and sustained response
for 11% of the cases, as did drug-associated neutropenia to corticosteroid therapy at immunosuppressive doses; some
(e.g., chemotherapy, phenobarbital, antibacterials); primary dogs also received additional immunosuppressive drugs. The
bone marrow disease was found in 4% of the patients. The neutropenia relapsed in 34% of the dogs on discontinuation
cause of the neutropenia was unclear in 21% of the patients. of the immunosuppressive treatment.
Border Collies commonly have neutropenia; this syndrome Clinical signs in neutropenic cats and dogs are usually
has been described as the trapped neutrophil syndrome, an vague and nonspecific; they include anorexia, lethargy,
autosomal recessive trait caused by a mutation in the VPS13B pyrexia, and mild gastrointestinal tract signs, as described