Emery-Dreifuss Muscular Dystrophy – Symptoms Diagnosis And Treatment

Emery-Dreifuss Muscular Dystrophy

First described in 1900 and then considered  the benign form of Duchenne muscular dystrophy, Emery-Dreifuss disease becomes a distinct clinical entity in 1966. So far, have been described two forms of Emery-Dreifuss muscular dystrophy: a X-linked recessive form and an autosomal dominant form.

X-linked recessive form occurs through a genetic mutation that consists of total absence of emerin, a muscle protein. Emerin is a nuclear membrane protein that is found mainly in skeletal muscle and cardiac muscle, but also in other tissues such as skin, colon, testes, ovaries and pancreas. The exact role of this protein is not fully understood, but is considered to participate in stabilizing the nuclear membrane against mechanical stress during muscle contraction. X-linked form of the disease affects mainly males.

Emery-Dreifuss Muscular Dystrophy

Autosomal dominant form appears through a genetic defect located on chromosome 1. Affected gene encodes a series of proteins called lamins A and C. These proteins are intermediate filaments found in the inner nuclear membrane and nucleoplasm of almost all cells of the body. Lamins have complex functions because they are providing mechanical strength to the nucleus, are involved in the determination of nuclear shape, and in the process of anchoring and spacing nuclear pore complexes. Lamins A and C possess an essential role in DNA replication and mRNA (mitochondrial RNA) transcription. This form of the disease is associated  with dilated cardiomyopathy and rhythm disturbances, most frequent arrhythmia being atrionentricular block . This form of Emery-Dreifuss myopathy affects both sexes equally.

Emery-Dreifuss Muscular Dystrophy Symptoms

Onset in X-linked form can occur at any stage of life, starting with the neonatal period, until the third decade of life. Emery-Dreifuss myopathy usually begins in adolescence. The most common signs are the appearance of muscle contracture and muscle weakness. Cardiac damage occurs much later, after striated muscle was affected and occurs most commonly around the age of 40 years.

The disease is characterized by a symptomatic triad:

• Muscle weakness and wasting in a scapulohumeroperoneal distribution;
• Early contractures of the elbow, ankle, and posterior neck;
• Cardiac conduction defects, cardiomyopathy, or both.

Contractures of the elbow and the cervical spine are suggestive for the disease  and later in evolution entire spine is affected causing stiffness. Peroneal muscle damage will lead to toe walking. Brachial biceps and triceps are affected in early stages of the disease.

Emery-Dreifuss Muscular Dystrophy Symptoms

Cardiac damage usually occurs in the second or third decade of life and is characterized by:

• Usually begins after onset of weakness and manifests as syncope in the second or third decade of life;
• Sudden cardiac death may be the first sign of cardiac damage;
• Pacemakers are needed by the age of 30 years;
• Atrial paralysis, bradycardia, atrial arrhythmias (atrial fibrillation, atrial flutter), atrioventricular conduction defects and ventricular cardiomyopathy represent signs of cardiac damage;
• 10-20% of female carriers in X-linked form of the disease present atrial arrhythmias or conduction defects and need ECG monitoring, once a year to prevent sudden cardiac death.

Emery-Dreifuss Muscular Dystrophy Diagnosis

Serum creatine is moderately increased in this form of the disease, if are present values of 50-100 times higher than normal, the diagnosis should be reconsidered as Duchenne myopathy or facioscapulohumeral muscular dystrophy.

Electromyography shows diminished or absent spontaneous muscle activity and  motor units present an activity of short duration and low amplitude. It is important to examine the most affected muscles.

Muscle biopsy is characteristic for muscle diseases with excessive variations in the diameter of muscle fibers, muscle fibers are hypertrophied, central nuclei,  excessive interstitial fibrosis and necrotic muscle fibers undergoing regeneration. Immunohistochemical study using emerin antibodies confirm the diagnosis by showing no nuclear staining. However muscle biopsy should be correlated with clinical data.

Emery-Dreifuss Muscular Dystrophy – Muscle Biopsy

Emery-Dreifuss Muscular Dystrophy Treatment

Emery-Dreifuss muscular dystrophy has no specific treatment. Are recommended procedures that are maintaining muscle activity, skeletal abnormalities correction, scoliosis and muscle contractures correction.

Due to the fact that atrial conduction disturbances and sudden cardiac death are the most important complications of the disease, prevention and treatment are required by the following procedures:

• Patients with bradycardia should benefit from pacemaker implantation;
• Intra-atrial thrombus, cerebral embolization and cardiomyopathy may still occur even in patients with pacemaker and for this reason, prophylaxis of this complications is required;
• Patients with progressive and untreatable cardiomyopathy should undergo cardiac transplantation;
• Ventricular arrhythmias may occur in the disease evolution and for this reason a cardioverter-defibrillator should be inserted.

Orthopedic treatment is aimed to maintain patient mobility for as long as possible and is needed to correct or to prevent muscle contractures and to increase range of motion.

To ensure the best possible therapy for a patient with Emery-Dreifuss muscular dystrophy is needed a approach team that is including a neurologist, pulmonologist, cardiologist, orthopedic surgeon, physiatrist and a physical therapist.