Emery-Dreifuss muscular dystrophy (EDMD)
Incidence
It follow an X-linked pattern of inheritance although rare families with a similar clinical picture show autosomal dominant inheritance.
Clinical Characteristics
EDMD is a form of muscular dystrophy that follow an X-linked pattern of inheritance. EDMD is an X-linked myopathy distinct from DMD and BMD and is characterized by a specific pattern of contractures, cardiomyopathy, and slowly progressive muscle weakness in adult life. The basic defect in EDMD is unknown and will likely await the cloning of the gene. The EDMD gene has been localized to the end of the long arm of the X chromosome at band Xq28. Inheritance of EDMD is X-linked, although rare families with a similar clinical picture show autosomal dominant inheritance. The clinical features of EDMD are compared to those in BMD, the form with which it is most likely to be confused. Onset occurs in the first decade, with the initial features including toe walking, partial flexion of the elbows, and inability to fully flex the neck and spine. Recognition of this distinct pattern of contractures of the heel cords, elbows, and neck extensors, associated with a scapulohumeroperoneal distribution of weakness, is an early clue to diagnosis. The weakness spreads to involve other muscle groups, such as those of the hip, as the disease progresses. Another consistent feature of EDMD is a cardiac conduction defect that may, unless treated, lead to sudden death. Presymptomatic detection of heart involvement by means of regular electrocardiograms and the insertion of a cardiac pacemaker at an early stage may be lifesaving. Cardiac risk also appears high in some but not all female carriers. The neuromuscular wasting is mild and slowly progressive, with onset during adolescence, significant disability being rare before adult life. Early in the course of the disease the biceps and triceps are affected most prominently. Later difficulties are due mainly to weakness of the hip and knee extensors. In the lower extremities, distal muscles seem to be affected before the proximal ones, giving a humeroperoneal distribution. Laboratory studies in EDMD have been somewhat variable and controversial. Serum CK is usually elevated 3 to 10 fold over normal levels, considerably lower than that characteristic of DMD and BMD. Disparate EMG results have been recorded showing both myopathic changes and evidence of denervation, even within the same individual. Muscle biopsy changes, usually consistent with a myopathy, are also variable. It would appear, therefore, that prime importance should be given to the clinical features of the disease since the disparate EMG and histologic changes are poorly understood and may be resolved only after the underlying gene has been cloned and characterized.
Precipitants
no
Provocation Tests
no
Diagnostic Procedures
Laboratory studies in EDMD have been somewhat variable and controversial. Serum CK is usually elevated 3 to 10 fold over normal levels, considerably lower than that characteristic of DMD and BMD. It would appear that prime importance should be given to the clinical features of the disease since the disparate EMG and histologic changes are poorly understood.