X-Linked Emery-Dreifuss Muscular Dystrophy (EMD)
Emery-Dreifuss muscular dystrophy (EDMD) is a genetically heterogeneous disorder characterized by: 1) joint contractures with early childhood onset, 2) slowly progressing muscle weakness and wasting and 3) cardiac conduction defects. Typically, the presenting symptom of X-linked EDMD is joint contractures of elbows, Achilles tendon, and post cervical muscles. Loss of ambulation may result from severe contractures of the spine and lower limbs, but is rare in X-linked EDMD. Muscle weakness and wasting is slowly progressive until after the third decade of life. The initial muscle groups affected follow a humero-peroneal distribution and scapular and pelvic girdle muscles become affected later in the course of the disease. The presenting clinical signs of muscle weakness include toe-walking and a waddling gait. Cardiac conduction defects are the most severe manifestation of EDMD, and female carriers without signs of skeletal muscle weakness or of contractures have been reported with cardiac disease (Emery., J Med Genet. 1989; 26: 637-641; Buckley et al., Heart. 1999; 82: 105-108). Cardiac disease can present in teenagers and includes conduction defects, dilated cardiomyopathy, and infiltration of the myocardium by fibrous and adipose tissue (Buckley et al., Heart. 1999; 82: 105-108). Serum CK levels are moderately elevated, most commonly in the early stages of disease (Bonne et al., Ann Neurol. 2000; 48: 170-180). Age of onset and disease severity demonstrate both inter-and intra-familial variability (Mercuri et al. Neurology.2000; 54: 1704-1705).
Physical therapy to preserve muscle tone, early implementation of a pacemaker, as well as proper use of cardiac drug therapies can be greatly improve the quality of life for affected patients (Bonne et al., European Journal of Human Genetics 2002; 10(3): 157-161). Furthermore, genetic testing can decrease mortality for at risk carriers who may not show any outward clinical features.
EMD carriers harbor considerable cardiac risk even without manifesting muscle weakness or other symptoms (Jensen V., Canadian Journal of Anesthesia. 1996; 43(9): 698-671). In affected men and carrier women, myocardium is often replaced with adipose or fibrous tissue which eventually leads to sudden death. For this reason, female carriers and affected males should be identified and evaluated early (Fishbein et al., Ann Intern Med. 1993; 119(9): 900-905).
Studies show the most effective way to reduce contracture occurrence and slow muscle degeneration is through passive range of motion physical therapy. The earlier this therapy is implemented directly correlates with slower muscle degeneration, fewer complications, and a higher quality of life (Emery-Dreifuss Muscular Dystrophy. 2013; mda.org).
Without the insertion of a pacemaker, atrial block and arrhythmias are likely and will result in death (Bonne et al., European Journal of Human Genetics. 2002; 10(3): 157-161). Cardiac defibrillators have been shown to reduce mortality by detecting life-threatening events that were then resolved (Bonne and Quijano-Roy, Hanb Clin Neurol. 2003; 113: 1367-1376).
Since they have proven to protect against the recurrence of life-threatening arrhythmias in EDMD patients, early application of antiarrhythmic drugs serve as an effective therapeutic objective (Graboys et al., The American Journal of Cardiology. 1982; 50(3): 437-443). Antithromboembolism drugs are also highly recommended to treat atrial fibrillation/flutter and atrial standstill. If these conditions are left untreated, debilitating embolic stroke is common at a young age, making early diagnosis and therapy implementation crucial (Borlani et al., Stroke. 2003; 34: 901-908).
For more information on EMD testing, please see our full Test Description.
This article is a summary of information that has been reported in the biomedical research literature.It is not medical advice for patients. All disease treatments should be under the direction of a qualified healthcare provider.