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Differential Diagnosis: Thrombocytopenia

Julie Allen, BVMS, MS, MRCVS, DACVIM (SAIM), DACVP, Cornell University

Internal Medicine

|June 2020|Peer Reviewed

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Differential Diagnosis: Thrombocytopenia

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.


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