Complement 3 Deficiency

Complement 3 Deficiency (C3D) is a disease that causes severe immunodeficiency, leaving affected dogs vulnerable to infections.

Key Signs

Recurrent bacterial infections, Renal disease

Age of Onset

At birth

Present at birth


Autosomal Recessive

For autosomal recessive disorders, dogs with two copies of the variant are at risk of developing the condition. Dogs with one copy of the variant are considered carriers and are usually not at risk of developing the disorder. However, carriers of some complex variants grouped in this category may be associated with a low risk of developing the disorder. Individuals with one or two copies may pass the disorder-associated variant to their puppies if bred.

Likelihood of the Condition

High likelihood

At risk dogs are highly likely to show signs of this disease in their lifetime.

What to Do

Here’s how to care for a dog with C3D

Partner with your veterinarian to make a plan regarding your dog’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.

For Veterinarians

Here’s what a vet needs to know about C3D

Deficiency in C3 predisposes an affected puppy to recurrent bacterial infections at an early age and to renal amyloidosis or Type 1 membranoproliferative glomerulonephritis. C3 deficient puppies also have an increased risk of developing hereditary renal and muscular disease (familial juvenile glomerulonephropathy and hereditary canine spinal muscular atrophy).

Treatment is supportive care and antibiotics as needed to treat infections that arise. Additionally, an affected dog should be monitored for developing kidney and muscle diseases.

For Breeders

Planning to breed a dog with this genetic variant?

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This disease is autosomal recessive meaning that two copies of the mutation are needed for disease signs to be shown. A carrier dog with one copy of the C3D mutation can be safely bred with a clear dog with no copies of the C3D mutation. About half of the puppies will have one copy (carriers) and half will have no copies of the C3D mutation. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. Please note: It is possible that disease signs similar to the ones caused by the C3D mutation could develop due to a different genetic or clinical cause.

Technical Details

Gene C3
Variant Deletion
Chromosome 20
Coordinate 53,573,746

All coordinates reference CanFam3.1

References & Credit

Credit to our scientific colleagues:

Johnson, J. P., McLean, R. H., Cork, L. C., & Winkelstein, J. A. (1986). Animal model: Genetic analysis of an inherited deficiency of the third component of complement in Brittany spaniel dogs. American Journal of Medical Genetics, 25(3), 557–562. View the article

Ameratunga, R., Winkelstein, J. A., Brody, L., Binns, M., Cork, L. C., Colombani, P., & Valle, D. (1998). Molecular analysis of the third component of canine complement (C3) and identification of the mutation responsible for hereditary canine C3 deficiency. Journal of Immunology. View the article