Evaluation of clinicopathologic features, response to treatment, and risk factors associated with idiopathic neutropenia in dogs: 11 cases (1990–2002)

Immune-Mediated Neutropenia in a Miniature Poodle

A 10 yr old spayed female toy poodle was presented to a tertiary referral center for a 10 day history of waxing and waning lethargy, vomiting, diarrhea, and anorexia. An immune-mediated neutropenia (IMN) was suspected to be the underlying cause of her clinical signs. A bone marrow aspirate was obtained from the chostochondral junction of the 11th and 12th ribs on the right side and provided a definitive diagnosis of IMN. A positive response to therapy and repeat blood work further confirmed the diagnosis. Obtaining bone marrow aspirates from the chostochondral junction is a safe, cheap, and reliable method of diagnosing IMN and can be performed in the private practice setting with light sedation and minimal need for specialized equipment.

[Neutropenia in dogs: etiology and prognostic factors]

OBJECTIVE

The aim of this retrospective study was to evaluate frequency, prognostic factors, and differences for various etiologies of neutropenia in dogs.

MATERIAL AND METHODS

A total of 391 dogs with neutrophil counts < 2.78 x 10⁹/l (January 2008 to December 2012) were included and, depending on the etiology of neutropenia, assigned to seven diagnostic groups: nonbacterial infectious disease, increased demand due to marked inflammation, drug-associated, bone-marrow diseases, immune-mediated, physiologic, miscellaneous. Absolute neutrophil counts, evidence of neutrophil toxicity or left shift, case history, rectal temperature, hospitalization, and survival were compared among groups.

RESULTS

Increased demand due to marked inflammation (90/391, 23%) and nonbacterial infectious disease (70/391, 18%) were the most common causes for neutropenia, followed by drug-associated neutropenia (43/391, 11%) and bone-marrow disease (32/391, 8%). Immune-mediated and physiologic neutropenia (both 16/391, 4%) were uncommon. Almost one third (124/391, 32%) of dogs were assigned to the miscellaneous group. Absolute neutrophil counts were significantly higher (p < 0.01) in dogs of the physiologic and miscellaneous groups than in the other groups. Dogs with immune-mediated neutropenia or nonbacterial infectious disease displayed significantly lower absolute neutrophil counts than dogs with neutropenia due to an increased demand (p < 0.001) and were most commonly referred with a history of fever (11/16, 69%) or gastrointestinal signs (52/70, 74%), respectively. Neutrophil toxicity and left shift were most commonly associated with an increased demand due to marked inflammation (60/90 and 25/90, 67% and 28%, respectively) and the mortality rate was highest in this group (32/90, 36%).

CONCLUSION

Neutrophil toxicity and left shift are associated with an increased demand due to marked inflammation and may indicate a poor prognosis. The lower the absolute neutrophil count, the greater the probability of an immune-mediated neutropenia.

CLINICAL RELEVANCE

Neutropenia should be assessed in context with case history, clinical examination, and neutrophil morphology.

Alloimmune neonatal neutropenia and neonatal isoerythrolysis in a Thoroughbred colt

A 3-day-old Thoroughbred colt was originally presented for treatment of neonatal isoerythrolysis, which was treated with a blood transfusion. However, persistent neutropenia was observed despite the absence of detectable infection. Subsequently, a granulocyte agglutination test was performed by incubating the colt's neutrophils with the mare's serum; results were positive, leading to a clinical diagnosis of alloimmune neonatal neutropenia. The diagnosis was further supported via flow cytometric analysis. The colt was hospitalized and treated prophylactically with antimicrobials and 4 separate doses of recombinant human granulocyte colony-stimulating factor (rhG-CSF; 1.4-3.5 µg/kg, subcutaneously) in attempts to maintain the neutrophil count within reference intervals over a 4-week period. The colt's neutrophil count increased after administration of rhG-CSF and eventually stabilized within reference intervals by day 20. The colt maintained normal neutrophil counts after discharge and was reportedly healthy at 6 months of age. Alloimmune neonatal neutropenia should be considered in foals with persistent neutropenia in the absence of infection. Alloimmune neonatal neutropenia can be treated with prophylactic antimicrobials combined with rhG-CSF with a favorable outcome.