Differential Diagnosis: Thrombocytopenia in Dogs & Cats

Following are differential diagnoses for patients presented with thrombocytopenia.*

• Breed-associated inherited macrothrombocytopenia 

  • Cavalier King Charles spaniels

  • Norfolk and cairn terriers

  • Identified sporadically in:

    • Bichons frises 

    • Boxers 

    • Chihuahuas 

    • Cocker spaniels 

    • English toy spaniels 

    • Havanese 

    • Jack Russell terriers 

    • Labradoodles 

    • Labrador retrievers

    • Maltese

    • Poodles 

    • Shih tzus

  • Inherited macrothrombocytopenia resulting from May-Hegglin anomaly (rare; reported in a pug crossbreed)

• Breed-associated thrombocytopenia

  • Akitas

  • Greyhounds

  • Other sight hounds (eg, whippets, deerhounds)

• Decreased platelet production

  • Acquired immune-mediated amegakaryocytic thrombocytopenia 

  • Aplastic anemia/bone marrow panhypoplasia 

    • Drug-associated effect (eg, chemotherapeutic, estrogen, griseofulvin [cats], chloramphenicol, sulfadiazine)

    • Infectious cause (eg, canine parvovirus, feline panleukopenia virus, FeLV, chronic Ehrlichia canis infection)

    • Other less common cause (eg, exposure to radiation, chemicals, mycotoxins, plant toxins)

  • Cyclic hematopoiesis in gray collies (ie, gray collie syndrome)

  • Myelophthisis (eg, myelofibrosis; lymphoid, myeloid, or metastatic neoplasia)

• Dilutional thrombocytopenia (eg, after massive transfusion, particularly of platelet-poor products)

• Gestational thrombocytopenia 

  • Occurs in humans, cows, and mice

  • May occur in dogs and cats 

• Increased platelet consumption

  • Disseminated intravascular coagulation

  • Envenomation (eg, snake bite)

  • Thrombotic microangiopathy (eg, thrombocytopenic thrombotic purpura, hemolytic uremic syndrome)

  • Vasculitis

• Increased platelet loss

  • Hemorrhage (eg, secondary to anticoagulant rodenticide toxicity or trauma)

• Increased platelet sequestration

  • Splenomegaly (eg, due to hypersplenism secondary to portal hypertension)

  • Splenomegaly ± hepatomegaly (eg, hypothermia, endotoxemia)

  • Other blood pooling

• Platelet destruction

  • Immune-mediated thrombocytopenia

    • Primary (ie, no underlying disease identified)

    • Secondary (eg, infection, neoplasia, drug-associated effect)

  • Non-immune–mediated platelet destruction, often due to infection (eg, rickettsial disease [eg, anaplasmosis, ehrlichiosis]), protozoal infection (eg, babesiosis), drugs, or neoplasia 

    • Hemophagocytic syndrome or lymphohistiocytosis

• Pseudothrombocytopenia, possibly due to:  

  • EDTA 

    • Platelet satellitism and/or phagocytosis

  • Overlap in size between RBCs and platelets (depending on methodology of platelet enumeration)

  • Platelet clumping (especially in cats)

*The pathogenesis of thrombocytopenia is often multifactorial. Thrombocytopenia associated with neoplasia, infectious disease, liver disease, and drug administration often has a complex mechanism with multiple contributing factors.

Editor's note: This article was originally published in June 2020 as "Differential Diagnosis: Thrombocytopenia"