MYBPC3 genetic test in Maine Coon and Ragdoll cats: interpretation
A Maine Coon breeder asks for advice on her breeding programme. She has tested all her cats for the A31P mutation in the MYBPC3 gene and wants to know its value.
Which statement is correct?
chevron_right Show answer and explanation
A. Every heterozygous cat will develop severe HCM before 5 years of age
Penetrance is incomplete: many heterozygous cats never develop clinical HCM. The risk is clearly greater in homozygotes.
B. A negative result does not rule out HCM: other genetic causes exist, and breeding cats should have periodic echocardiographic screening
Correct. Cats negative for A31P (Maine Coon) or R820W (Ragdoll) can develop HCM. The test identifies one specific mutation; echocardiography, repeated through the breeding life, assesses the phenotype.
C. The A31P test is valid for any breed and for domestic shorthair cats
The mutations are breed-specific: A31P in Maine Coons and R820W in Ragdolls. In other breeds or mixed-breed cats a negative result provides no information.
D. A normal echocardiogram at one year of age guarantees the cat is free of HCM
HCM can appear years later. That is why screening is repeated (e.g. annually) throughout the breeding life.
lightbulb Key takeaway
Homozygotes for the mutation carry the highest risk and should not be bred. Removing all heterozygotes at once can greatly reduce the breed's genetic diversity; combine the test with periodic echocardiography.
References: ACVIM consensus statement guidelines for the classification, diagnosis, and management of cardiomyopathies in cats (2020)
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.