Familial left ventricular hypertrabeculation in myotonic dystrophy type 1

Familial left ventricular hypertrabeculation (LVHT)has not been described in myotonic dystrophy type 1 (MD1).

Two MD1 patients are described, father and daughter, both presenting with LVHT. The father was a 45-year-old man with the typical MD1 phenotype starting in 1992. DNA analysis revealed a heterozygous expansion of 300 CTG repeats in the myotonic dystrophy protein kinase (DMPK) gene on chromosome 19q13.3. He had a history of successful electrocardioversion of atrial flutter into sinus rhythm. Cardiac history and clinical cardiologic examination were otherwise normal. On ECG, ST elevation was found exclusively. Transthoracic echocardiography revealed LVHT, previously described only in Becker's muscular dystrophy, metabolic myopathy, Barth syndrome, and other rare genetic disorders. In the 13-year-old daughter, occasional muscle cramps since 1998, discrete weakness of the left triceps brachii muscle, and discrete distal wasting of the upper limbs were found. Serum creatine kinase (CK) and electromyography were normal. The daughter carried an expansion of 140 CTG repeats in the DMPK gene. Clinical cardiologic examination as well as the ECG were normal. Echocardiography revealed LVHT,which was also confirmed by cardiac MRI. Neither the father nor the daughter required any cardiac medication.

This study demonstrates that LVHT in MD1 may bea cardiac manifestation of the underlying skeletal muscle disorder, may show a familial occurrence, or may be associated with other cardiac abnormalities or isolated.