The characteristic symptom is ventricular hypertrophy which can lead to left ventricular outflow obstruction and to cardiac failure. It is sometimes a cause of sudden death in apparently healthy young individuals and is a common postmortem finding in young sportsmen and women who die suddenly while competing. Mutations in a number of genes have been implicated in its etiology. These include beta myosin heavy chain gene on chromosome 14, the cardiac troponin gene on chromosome 1, alpha-tropomyosin on chromosome 15, myosin binding protein C and at least one more as yet undiscovered locus. The common factor is that all four discovered genes are components of the sarcomere.
Many cases have no previous known family history.
Most mutations are missense which means that they result from perhaps just a single nucleotide substitution. Some mutations are invariably of severe effect, others are much less likely to cause sudden death and they are sometimes passed on without having caused any symptom. A male cinammon tabby cat is crossed to a brown tabby cat. All the offspring are brown tabbies. The same male is crossed to another brown tabby.