Primary immunodeficiency with MAC susceptibility (CARD9-related) - Miniature Schnauzer

What does this test examine?

This genetic test analyses the CARD9 c.493_495del deletion in the Miniature Schnauzer. The condition is best described as CARD9-related primary immunodeficiency, MAC susceptibility, susceptibility to Mycobacterium avium complex and inherited immune dysfunction in the Miniature Schnauzer.

CARD9 has a central role in immune signalling. The c.493_495del deletion removes one amino acid from the CARD9 protein and disrupts an immune pathway needed to control certain infections.

What does this condition mean?

Mycobacterium avium complex consists of environmental bacteria that healthy dogs usually resist well. Dogs with CARD9-related immunodeficiency can instead develop severe systemic infection. Reported signs include fever, lethargy, weight loss, diarrhoea, enlarged lymph nodes, enlarged liver or spleen, anaemia and lameness. This is therefore not just an infection test, but an inherited susceptibility test for an important immune defect.

Inheritance and result

The trait is inherited as autosomal recessive. Two copies of the CARD9 deletion cause the tested immunodeficiency. Carriers have one copy, are generally not affected themselves, and can pass the variant on.

What does the result mean?

• Clear (N/N): the tested CARD9 deletion was not detected.
• Carrier (N/del): the dog carries one copy and can pass the variant on.
• Affected (del/del): two copies cause the CARD9-related immunodeficiency with severe MAC susceptibility.

Practical value of this test

• The test identifies hidden carriers in Miniature Schnauzer lines.
• Breeders can avoid carrier-to-carrier matings and prevent puppies with this immunodeficiency.
• When there is a family history of MAC infection, the result gives direct information for line management.
• For young dogs, the test gives clarity on clear, carrier or affected status before breeding use.
• A two-copy positive result shows that the issue is a genetic immune defect, not only exposure to an environmental bacterium.

Using this test as an immunodeficiency analysis makes the practical meaning clearer for breeders and veterinarians: it helps prevent an inherited immune defect that enables severe MAC infections.