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Published on: March 29, 2020
Extreme thrombocytosis in a young cat
Emma Hooijberg1, Ernst Leidinger1, Georges Kirtz1
1Labor InVitro, Rennweg 95, Vienna, 1030 Austria.
Insights
A feline panleukopenia virus and feline calicivirus coinfection led to extreme thrombocytosis in a young cat. This case highlights unusually high platelet counts, prompting discussion on reactive versus neoplastic causes in feline medicine.
Area of Science:
- Veterinary Medicine
- Infectious Diseases
- Hematology
Background:
- A 7-month-old domestic shorthair cat presented with inappetence, hypersalivation, fever, gingivitis, and oral ulceration.
- Initial diagnostics revealed leukopenia, neutropenia, and elevated titers for feline panleukopenia virus (FPV) and feline calicivirus (FCV), suggesting a coinfection.
Purpose of the Study:
- To investigate the cause of severe, persistent thrombocytosis in a young cat coinfected with FPV and FCV.
- To explore potential differential diagnoses, including reactive thrombocytosis and essential thrombocythemia, for the observed extreme platelet count.
Main Methods:
- Clinical examination and serological testing for FPV and FCV.
- Complete blood count (CBC) and blood smear examination to assess platelet levels.
- Monitoring of platelet count over time (day 10 and day 35 post-initial presentation).
Main Results:
- The cat exhibited severe leukopenia and neutropenia, consistent with FPV and FCV coinfection.
- A marked thrombocytosis was observed, with platelet counts reaching 3,448 × 10^9/L (day 10) and 4,990 × 10^9/L (day 35), significantly exceeding the reference range.
- The extreme and persistent thrombocytosis prompted consideration of reactive causes versus essential thrombocythemia, a diagnosis of exclusion.
Conclusions:
- The case presents an unprecedented level of persistent thrombocytosis in a feline coinfection scenario without a confirmed neoplastic process.
- While infection can cause reactive thrombocytosis, the magnitude and duration in this case warrant further investigation into underlying pathophysiology.
- This case underscores the importance of considering extreme hematological responses in feline infectious diseases and the diagnostic challenges they present.
Abstract:
A 7-month-old unvaccinated domestic shorthair cat was presented with a history of inappetence and hypersalivation. Clinical examination revealed fever, gingivitis and oral ulceration. An initial blood sample revealed a severe leukopenia and neutropenia and a feline panleukopenia virus (FPV) titre of 1:640; a second titre 10 days later was 1:2,560. A feline calicivirus (FCV) titre was 1:320 and the initial clinical signs and laboratory findings were attributed to a coinfection with FPV and FCV. The cat was treated with interferon omega. A blood sample taken 10 days later revealed a severe thrombocytosis of 3,448 × 109/L (reference range 200-500 × 109/L) confirmed by blood smear examination. The platelet count on day 35 was 4,990 × 109/L. No bone marrow examination was carried out. Two differential diagnoses for an extreme thrombocytosis are a reactive thrombocytosis or essential thrombocythemia (ET). ET is a hemic neoplasia that causes a severe and persistent thrombocytosis, and is a diagnosis of exclusion. Reactive thrombocytosis is generally mild to moderate and of shorter duration than described here, but an excessive response could have been caused by infection. The influence of additional factors such as an initial thrombocytopenia, age and interferon treatment are not clear but can be speculated on. Although the exact pathophysiology in this case remains unclear, such high, persistent thrombocyte numbers have not been reported in cats in the absence of a neoplastic process.
