Maine Coon Hypertrophic Cardiomyopathy (HCM): Early Detection & Care

The MYBPC3 MutationFeline HCM in Maine Coons is caused by a single base-pair change (G→C) in the cardiac myosin binding protein C gene (MYBPC3) — the A31P mutation. The inheritance pattern is autosomal dominant with incomplete penetrance: not all cats with one copy of the...

The MYBPC3 Mutation

Feline HCM in Maine Coons is caused by a single base-pair change (G→C) in the cardiac myosin binding protein C gene (MYBPC3) — the A31P mutation. The inheritance pattern is autosomal dominant with incomplete penetrance: not all cats with one copy of the mutation develop clinical disease, but homozygous cats (two copies) develop severe HCM at a young age. The mutation is present in approximately 34% of Maine Coons worldwide, with homozygous frequency of approximately 5%.

Screening Protocol

• Annual echocardiography (cardiac ultrasound) starting at age 1 — measure left ventricular wall thickness in diastole (normal <5.5mm)
• NT-proBNP blood test — cardiac biomarker elevated when heart muscle is under stretch stress; screening test, not diagnostic
• Genetic testing identifies mutation carriers but cannot predict disease severity — echocardiography remains the gold standard
• Auscultation alone is inadequate: up to 40% of HCM-affected cats have no audible murmur

Clinical Signs of HCM

Many affected cats are asymptomatic until sudden death or acute heart failure. Warning signs: increased respiratory rate at rest (>30 breaths/minute at home), open-mouth breathing, hind-limb paralysis from aortic thromboembolism (saddle thrombus — a blood clot lodges at the aortic bifurcation, cutting off blood flow to hind legs; this is excruciatingly painful and has a poor prognosis), lethargy, and decreased appetite. Any Maine Coon exhibiting these signs needs emergency veterinary evaluation within hours.

References & Further Reading

• ASPCA. Common Dog & Cat Behavior Issues. aspca.org/pet-care
• American Animal Hospital Association (AAHA). Pet Behavior Resources. aaha.org
• Journal of Veterinary Behavior (Elsevier). Clinical Applications and Research. sciencedirect.com
• American Veterinary Society of Animal Behavior (AVSAB). Position Statements & Resources. avsab.org

Citations are provided for educational reference. Content is reviewed periodically but does not replace professional veterinary advice. If your pet shows signs of illness, contact a licensed veterinarian immediately.