Earliest age when HCM in Maine Coons can be detected

Beautiful Maine Coon ginger tabby kitten but are they predisposed to HCM? Image: Photo: Viktoria Vyacheslavovna Terskaya.

My research using clinical studies informs me that the disease usually appears around 6 months of age but perhaps as early as 3 months of age according to one American hospital.

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The first study I looked at describes the development and characteristics of a colony of Maine coon cats that had familial hypertrophic cardiomyopathy (FHCM), a genetic heart disease. The researchers bred affected and unaffected cats to determine the mode of inheritance of the disease and used echocardiography to identify affected offspring and determine the natural history of the disease. 

The results showed that the disease follows an autosomal dominant pattern of inheritance with 100% penetrance, meaning that individuals who carry the genetic mutation for the disease will develop it. The disease usually appears in cats around 6 months of age and becomes more severe in young adulthood. Affected cats often die suddenly or from heart failure.

The study: Familial Hypertrophic Cardiomyopathy in Maine Coon Cats published on AHA Journals.

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Glencoe Animal Hospital says that "HCM is a progressive disease and can be found in kittens as early as 3 months of age and adult cats well into their senior years."

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In one study, they confirmed that the severity of the disease varied among the affected cats in the study, with some having milder symptoms and others having more severe symptoms. The age at which the disease developed also varied, with some cats developing the disease earlier in life and others developing it later.

"Most of the cats had echocardiographic evidence of HCM by 2–3 years of age, but one female (heterozygote) did not have echocardiographically identifiable disease until 7 years of age"

The genotype, or the specific genetic makeup, of the cats also seemed to affect the clinical outcome of the disease, with cats that had two copies of the mutated gene (homozygotes) developing more severe disease and dying at a younger age than cats with only one copy of the mutation (heterozygotes). Some of the cats with a homozygous mutation died suddenly, which suggests that they may have been at an increased risk of sudden cardiac death.

The study: A cardiac myosin binding protein C mutation in the Maine Coon cat with familial hypertrophic cardiomyopathy.

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How common is it? A study reports: "The true prevalence within the breed is not known, however it may be as high as 9.5-26.3%."

The study: Hypertrophic cardiomyopathy in young Maine Coon cats caused by the p.A31P cMyBP-C mutation - the clinical significance of having the mutation.

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Another source: Universities Federation for Animal Welfare, states: "About 30% of Maine coon cats have a genetic mutation that makes it likely that they will develop hypertrophic cardiomyopathy."