ASG

1. Referral:

“Topper,” a four year old spayed female miniature schnauzer presented for a weeklong history of lethargy and anorexia. The owners also felt that she had been polydipsic for the past few days. Referral bloodwork revealed neutropenia but no other abnormalities.

2. Exam:

Topper was quiet, alert and responsive. Her temperature was quite elevated at 105.3°F. Pulse and respiration were within normal limits at 130 bpm and 36 bpm respectively. Thoracic auscultation was within normal limits; abdomen was tense but non-painful on palpation. The rest of the physical exam was unremarkable.

3. Initial Problem List:

Our initial concerns for Topper included anorexia, fever and neutropenia. Fever can be caused by inflammatory, infectious, immune-mediated or neoplastic diseases. Anorexia can stem from a variety of conditions. Given Topper was displaying other systemic signs, her anorexia most likely was the result of the same underlying process so our work-up focused on the source(s) of her fever and neutropenia. Neutrophils, like other blood cells, can be decreased secondary to sequestration/consumption, destruction or decreased production (bone marrow disorders).

4. Diagnostics:

Initial diagnostics included a full senior screen to look for any evidence of other systemic disease. Globulins were slightly increased at 4.0, consistent with inflammatory, infectious or neoplastic conditions. Neutrophils were extremely low at 1064. Urine and blood cultures were performed to look for underlying infection and were negative. Thoracic and abdominal radiographs were unremarkable except for some decreased detail in the cranial abdomen. Abdominal ultrasound showed a hyperechoic gall bladder wall, but no findings that could account for the fever or neutropenia.

While performing diagnostics and waiting for results, Topper was admitted to the hospital and treatment begun for sepsis or other overwhelming infection. In addition to intravenous fluids, Topper was started on broad- spectrum antibiotics (Unasyn and Enrofloxacin). Due to her prolonged anorexia, a nasogastric feeding tube was also placed and enteral nutrition delivered.

Despite fluids and antibiotics, Topper remained quite febrile (>104°F) over the next 72 hours. Tick serology was performed (later to be found negative). Three days after admittance to the hospital, neutrophils were even lower at 608. The owner elected to have a bone marrow aspirate evaluated to look for an underlying bone marrow disease. This was felt to be less likely, given normal red cell counts and platelets. The bone marrow was markedly hyperplastic with a maturation arrest at the segmented granulocyte stage. These findings were considered most consistent with an immune-mediated neutropenia.

5. Discussion:

Immune-mediated neutropenia is an uncommon condition in the dog, and can be primary or secondary. In veterinary patients, immune-mediated neutropenia is diagnosed primarily by ruling out other causes of neutropenia. In this case, Topper was diagnosed with primary immune-mediated neutropenia. There was no known history of drugs, toxins or other disease processes to have elicited an immune response. In a retrospective study of 11 dogs[1], the patients with immune-mediated neutropenia had significantly lower neutrophil counts than were found in dogs with neutropenia attributable to other causes. Topper’s results were consistent with this finding, with a neutrophil nadir of 608.

6. Treatment:

Topper was started on an immunosuppressive course of corticosteroids. She was discharged from the hospital on prednisone 2 mg/kg PO bid and with an esophageal tube in place so that the owner could continue nutritional support. Within 48 hours of starting therapy, Topper’s fever resolved and her neutrophils normalized at 4949. A week following discharge, Topper developed a neutrophilia with a left shift (39,000 neutrophils with 1000 bands). Broad spectrum antibiotics were reinstituted and prednisone was tapered to once daily. A week later, the bands resolved and there was only a mild neutrophilia (20,000). Topper was continued on once daily prednisone 2 mg/kg and completed the course of antibiotics.

7. Recovery:

Topper was diagnosed with immune-mediated neutropenia over three months ago. She is clinically doing very well and has a fabulous appetite. She has not had any further febrile episodes since discharge. At the time of this writing, her current neutrophil count is 12,324.

by Rhonda Schulman,
DVM, MDiplomate American College of Veterinary Internal Medicine

REFERENCE:  [1] Brown CD, Parnell NK, Schulman RL, Brown CG et al.  Evaluation of clinicopathologic features, response to treatment, and risk factors associated with idiopathic neutropenia in dogs:11 cases (1990-2002).  J Am Vet Med Assoc 2006;229:87-91.

*Photo of Miniature Schnauzer is not “Topper.”