A 11-year-old female with an autosomal dominant mutation in myosin-binding protein C is being evaluated by a pediatric cardiologist. The family history reveals that the patient’s father died suddenly at age 33 while running a half-marathon. What was the likely finding on histological evaluation of his father’s heart at autopsy?
1.Myocyte disarray
2.Amyloid deposits
3.Eosinophilic infiltration
4.Wavy myocytes
5.Viral particles
sol:
Based on the patient’s mutation and family history, the patient described above likely has Hypertrophic Cardiomyopathy (HCM). About half of HCM cases are due to an autosomal dominant genetic disease that, along with myocyte disarray, has the histological hallmarks of fibrosis and myocyte hypertrophy.
Several autosomal gene mutations in sarcomere proteins may lead to HCM, including myosin-binding protein C, beta-myosin heavy chain, and the cardiac troponins. These mutations result in a decrease in the effectiveness of cardiac contraction, thereby increasing the amount of work the heart must perform. This leads to the enlargement of the heart and the histological manifestations described above (myocyte proliferation, hypertrophy, and disarray).
Elliot and McKenna state that HCM is a common genetic disease, defined by the presence of unexplained left ventricular hypertrophy. They note that the chances of complications depends on risk factors such as specific genetic mutations, age, myocardial pathology, and other pathophysiological abnormalities such as impaired peripheral vascular responses.
Wexler et al. note that HCM is caused by 11 mutant genes with more than 500 individual transmutations. According to the authors, the most common mutations are in the beta-myosin heavy chain and in the myosin-binding protein C.
Illustration A demonstrates myocyte proliferation and myocyte disarray; this is very characteristic of HCM