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Relatively benign congenital muscular dystrophy usually beginning in childhood or adolescence and characterized by early muscle contractures (mainly shoulders and upper arms) and cardiac conduction disorders.

Scapuloilioperoneal Atrophy with Cardiomyopathy.

No precise data are available. The X-linked form (males only) is more frequent and has been reported in more than 70 families. The estimated prevalence is approximately 1:100,000 in the general population. The autosomal dominant form is much less frequent.

Two forms of EDMD exist: (1) X-linked, resulting from a mutation in the emerin gene (>100 mutations have been reported and mapped to X28q) that usually results in complete absence of emerin from the muscles, and (2) autosomal dominant, resulting from a mutation in the lamin A/C gene on 1q21. Lamins A/C are part of the nuclear lamina, a fibrous layer on the nucleoplasmic side of the inner nuclear membrane, where they interact with chromatin and other proteins of the inner nuclear membrane (lamina-associated proteins and emerin) through various binding sites. Significant intrafamilial and interfamilial variability have been described. Sporadic cases have been described.

Almost all known mutations result in a complete absence of emerin, an inner nuclear membrane protein not limited to muscle cells but mostly expressed in skeletal and cardiac muscles. It is believed to interact with the nuclear lamins (components of the nuclear lamina), chromatin, and nuclear actin. Its exact role is unknown, but it seems to protect the nuclear membrane from mechanical lesions during muscle contraction. It also may favor reassembly of the nuclear membrane at the end of mitosis. Lamins A/C is also an inner nuclear membrane protein with properties similar to emerin, which would account for the similarity in phenotype between X-linked and autosomal dominant EDMD. For emerin (and presumably lamins A/C) to function properly, the protein must be correctly positioned on the nuclear membrane. Any defect in the nuclear membrane could interfere with skeletal muscle regeneration because emerin seems to play an important role in the organization of the nuclear membrane during cell division. Emerin seems to be associated with cardiac desmosomes and fasciae adherentes, which not only suggests a physiologic role for the protein in cardiac function but also explains the cardiac involvement.

Mainly based on the clinical findings. It is easier to diagnose if a relative has the disease. Serum creatinine kinase levels are moderately increased. Electromyography and nerve conduction studies confirm the myopathic nature of the disease. Muscle biopsy using antibodies to emerin can help confirm the diagnosis in the X-linked form.

The two forms of the disorder are clinically similar. Onset of the clinical manifestations usually occurs in the second or third decade of life. The following triad characterizes the disorder. (1) Early contractures affecting the Achilles tendons (resulting in toe walking), elbows (biceps and triceps), and posterior cervical muscles (initially resulting in limited cervical flexion, which later extends to the whole spine) often occur before any muscle ...

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