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Hypertrophic cardiomyopathy in congenital myotonic dystrophy
H Igarashi1, M Y Momoi, T Yamagata
1Department of Pediatrics, Jichi Medical School, Minamikawachi, Tochigi, Japan.
Insights
Congenital myotonic dystrophy can cause severe heart muscle damage, leading to fatal left ventricular hypertrophy. Larger CTG repeat expansions in the myotonin kinase gene may correlate with this extreme cardiac manifestation.
Area of Science:
- Cardiology
- Genetics
- Neuromuscular Disorders
Background:
- Myotonic dystrophy commonly affects the cardiac conduction system.
- Primary myocardial abnormalities are infrequently reported in myotonic dystrophy patients.
Observation:
- A severe case of congenital myotonic dystrophy presented with fatal left ventricular hypertrophy by 3 months of age.
- Progressive left ventricular hypertrophy and outflow obstruction were observed via serial ultrasonography.
- Genetic analysis revealed a significantly large 5.8 kb CTG repeat expansion in the myotonin kinase gene.
Findings:
- The patient exhibited an extreme level of myocardial damage, manifesting as left ventricular hypertrophy.
- The extensive CTG repeat expansion suggests a correlation between repeat size and the severity of cardiac involvement.
Implications:
- Left ventricular hypertrophy may represent a severe, albeit rare, cardiac manifestation of myotonic dystrophy.
- The size of CTG repeat expansions could be a key factor in determining the extent of myocardial damage in congenital myotonic dystrophy.
Abstract:
Involvement of the cardiac conduction system is a common clinical feature in myotonic dystrophy, whereas the association of primary myocardial abnormalities has rarely been reported. A patient with a severe form of congenital myotonic dystrophy who developed fatal left ventricular hypertrophy at 3 months of age and died at 2 years of age is reported. Serial ultrasonographic studies revealed progressive left ventricular hypertrophy accompanied by outflow obstruction of the left ventricle. Southern analysis for the myotonin kinase gene revealed a 5.8 kb expansion of CTG repeats in addition to a fragment of normal length. The degree of expansion was much greater than those of other reported patients with congenital myotonic dystrophy. These findings suggest that left ventricular hypertrophy represents an extreme level of myocardial damage in myotonic dystrophy and that this damage may be related to the larger size of the CTG repeats.