Complement 3 Deficiency, C3 Deficiency


Activation of the C3 protein triggers a "complement cascade," a form of immune defense, which tries to trap and tag invading microbes for destruction by immune cells. In the absence of functional C3, the cascade never begins. Dogs affected with this disease are highly susceptible to infections and kidney disease and must be monitored closely.

  • Signs and symptoms

    Affected dogs have recurrent bacterial infections that can affect any part of their body. Skin and respiratory infections most commonly occur. When kidney disease develops, increased thirst (polydipsia), increased urination (polyuria), and decreased appetite are often observed.

    Signs often first appear in puppies, and will continue throughout their life.

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  • Diagnosis

    Genetic and laboratory testing along with clinical signs are used to diagnose this disease.

  • Treatment

    Appropriate antibiotic therapy when infections occur and consistent monitoring of kidney parameters are the key to managing this condition. Once kidney disease begins, prescription diets and fluid therapy are required. There is no cure for this disease.

  • What to do if your dog is at risk


    • Even with the best of care, affected dogs have a shortened lifespan.
    • Preventing infections, giving medications appropriately, and following your veterinarian’s advice will give your affected dog the best possible life.

  • Genetic Information

    This mutation was first described in the Brittany Spaniel.

    This condition is inherited in an autosomal recessive manner, meaning that a dog must have two copies of the mutation to be affected.

    Gene names:

    C3 ‐ chr

    Inheritance type:


  • Breeds affected

    This health condition affects the following breeds

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