ITP in Dogs and Cats: Diagnostics & Therapeutics

Written By Moichor Clinical Pathology

Iridal petechiae observed in a dog with ITP. These ocular findings underscore the importance of complete ophthalmic examination in thrombocytopenic patients to detect subtle hemorrhagic complications.

Immune-mediated thrombocytopenia (ITP) is one of the most common acquired bleeding disorders in small animal practice. Caused by autoimmune destruction of circulating platelets, ITP can lead to severe thrombocytopenia and life-threatening hemorrhage. Early recognition, thorough diagnostics, and timely therapy are critical for improving outcomes.

Pathophysiology & Clinical Presentation

In ITP, the immune system produces antibodies against platelet surface antigens, marking them for destruction primarily in the spleen and liver. Complement-mediated lysis, impaired megakaryocyte function, and cross-reactivity with infectious agents can all contribute to the condition.

Clinically, patients often present with petechiae, ecchymoses, spontaneous bleeding (epistaxis, hematuria, melena), and prolonged bleeding from minor wounds. Secondary signs such as lethargy, pallor, tachycardia, and fever may accompany the hemorrhagic picture. Dogs are most commonly affected, but cats can also develop ITP, sometimes in association with underlying retroviral infection or neoplasia.

Diagnostic Approach

Diagnosis requires both confirmation of thrombocytopenia and exclusion of secondary causes.

  • CBC and blood smear remain essential first steps, with platelets typically <20,000/µL in primary ITP. Smear review helps identify platelet clumping (pseudothrombocytopenia), evaluates platelet size (large platelets imply regeneration), and screens for parasites.

  • Chemistry and urinalysis assess systemic health and rule out organ dysfunction.

  • Coagulation studies are usually normal, but they help exclude DIC.

  • Infectious disease testing (Ehrlichia, Anaplasma, RMSF, FeLV, FIV) is recommended in all cases.

  • Bone marrow aspirates are indicated in refractory cases, those with concurrent cytopenias, or atypical presentations; findings typically reveal an increase in megakaryocytes in ITP.

Advanced tests, such as anti-platelet antibody assays or flow cytometry, exist but have limited availability and clinical application.

Case Highlight: Primary ITP in a Golden Retriever

A 6-year-old spayed female presented with lethargy, petechiae, and ecchymoses. Platelet count was 8,000/µL with large platelets observed. Infectious disease panel was negative. Treatment with high-dose prednisolone resulted in platelet recovery to >100,000/µL within five days.
👉 A classic example of primary ITP with rapid steroid responsiveness.

Therapeutic Management

Emergency Stabilization

Patients with severe bleeding require minimal handling, padded housing, and close monitoring. Platelet transfusions may be lifesaving, but their effect is short-lived due to ongoing immune destruction.

First-Line Therapy: Corticosteroids

  • Prednisolone/Prednisone (2–4 mg/kg PO q12h) remains the gold standard.

  • Initial responses are expected within 3–7 days.

  • Once platelet counts stabilize at>150,000/µL for 7–10 days, gradual tapering begins.

In severe cases, IV dexamethasone is used initially until oral therapy is possible.

Second-Line & Rescue Options

For steroid-refractory patients or those requiring sparing strategies:

  • Azathioprine (delayed onset, careful monitoring needed)

  • Cyclosporine (faster onset, effective steroid-sparing agent)

  • Mycophenolate mofetil (emerging with promising efficacy)

  • Vincristine may cause rapid but temporary increases in platelet count by stimulating the release of platelets from megakaryocytes.

  • Splenectomy can be curative in selected refractory cases.

  • IVIG is reserved for critical, refractory patients due to cost.

Case Highlight: Secondary ITP from Ehrlichiosis

A 4-year-old German Shepherd with travel history presented with epistaxis, thrombocytopenia, and splenomegaly. Ehrlichia canis titers were positive. Treatment combined doxycycline with prednisolone, leading to platelet recovery over three weeks.
👉 Always test for vector-borne disease in thrombocytopenic dogs.

Monitoring & Long-Term Care

Frequent CBC monitoring (every 2–3 days initially) guides therapy. Most patients show recovery within 1–2 weeks. About 10–30% relapse, requiring either re-initiation of therapy or long-term immunosuppression.

Prognosis varies:

  • Primary ITP: 70–80% achieve remission.

  • Secondary ITP: Depends on the underlying cause.

  • Evans Syndrome (ITP + IMHA): Prognosis guarded, ~50–60% long-term survival.

Client Education

Owner compliance and monitoring are essential. Clients should be trained to recognize signs of relapse and when to seek emergency care:

  • Bleeding that won’t stop within 5 minutes

  • Blood in vomit, stool, or urine

  • Pale gums, collapse, or labored breathing

Stress the importance of strict medication compliance, activity restrictions, and routine rechecks.

Key Takeaways

  • Early diagnosis and prompt corticosteroid therapy remain the cornerstone of management.

  • Rule out secondary causes (infectious disease, neoplasia, drug reactions).

  • Have a tiered approach: start with corticosteroids, escalate to immunosuppressants or rescue therapies if needed.

  • Educate clients thoroughly, as relapse and long-term management are common realities.

With a systematic approach, most patients—especially those with primary ITP—have an excellent chance at remission and a return to normal quality of life.

📚 References:

Moichor Clinical Pathology
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