Genetic test for the A31P mutation of the MYBPC3 gene associated with hypertrophic cardiomyopathy (HCM) in the Maine Coon, corresponding to a G>C transversion ('HCM1' variant). HCM thickens the left ventricular wall and impairs diastolic function, with a risk of heart failure, thromboembolism and sudden death. It is the most common feline heart disease and in the Maine Coon it shows known familial aggregation. The test distinguishes clear, heterozygous and homozygous cats in order to make breeding decisions.

The Maine Coon is the breed with the most HCM data. The prevalence of A31P carriers was studied in the breed (Fries et al. 2008, PMID 18498321); the figures vary between studies and countries, so a single percentage should not be given (limited data). A significant part of the breed's HCM occurs in cats negative for this mutation.

- Frequently asymptomatic course for years\n- Heart murmur or gallop rhythm on auscultation\n- Dyspnoea, tachypnoea and orthopnoea in heart failure\n- Lethargy, anorexia and exercise intolerance\n- Arterial thromboembolism with acute painful paralysis of the hindlimbs\n- Sudden death, especially in young cats

Familial HCM in the Maine Coon was recognised in the early 1990s through familial aggregation studies and echocardiographic screening. In 2005, Meurs and colleagues identified the A31P mutation in the MYBPC3 gene (myosin-binding protein C), the first genetic marker of HCM in the feline species. Subsequent population studies showed that most heterozygotes remain healthy for years, which lowered the predictive value of the test in simple carriers. Today the test is maintained as a breeding tool, always combined with echocardiography.

- Test all breeding animals and record the result alongside the pedigree\n- Never mate two A31P carriers; homozygotes must be withdrawn from breeding\n- Heterozygotes, if kept in breeding, should only be mated with clear cats and with normal echocardiography\n- A negative test does not equal a healthy heart: continue annual echocardiographic screening\n- Withdraw from breeding any cat with HCM confirmed by imaging

The A31P mutation explains only part of Maine Coon HCM: its absence does not rule out the disease. In asymptomatic heterozygotes the result should be communicated as 'risk' and not as 'disease'. Differentiate from hyperthyroidism and arterial hypertension when faced with a hypertrophic pattern. Doppler echocardiography is the standard; NT-proBNP and troponin I help in the clinical assessment.

1. Meurs KM et al. 2005, mutación de MYBPC3 en el Maine coon con HCM familiar (PMID 16236761)
2. Fries R, Heaney AM, Meurs KM. 2008, prevalencia de la mutación de MYBPC3 en Maine coon (PMID 18498321)
3. Longeri M et al. 2013, variantes de MYBPC3 (A31P, A74T, R820W) y su asociación con HCM (PMID 23323744)
4. Gil-Ortuño C et al. 2020, genética de la HCM felina (PMID 32215921)
5. OMIA:000167 Cardiomiopatía hipertrófica felina