| Disease Name | autosomal dominant (AD) and autosomal recessive (AR) | | NMD Category | Myopathy - Disease of Muscle | | Clinical Onset | 40-60 years. | | Clinical Findings | This group of disorders includes several forms that are currently described by clinical phenotype: late adult onset myopathy with onset in hands (Welander); late adult onset myopathy with onset in legs (Markesbery and Griggs; Udd); early adult onset myopathy with onset in posterior compartment of lower legs (Miyoshi); early adult onset myopathy with onset in anterior compartment of lower legs (Nonaka); adult onset myopathy related to desmin storage and autophagocytosis.
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| | Diagnostic Work-up | Late adult onset myopathy with onset in hands (autosomal dominant): muscle imaging using CT or MRI shows involvement of lower leg muscles both in the anterior and posterior compartments. Muscle biopsy from anterior tibialis shows myopathic changes and occasional vacuolation. EMG is myopathic in early stages, but neurogenic changes have also been described in patients with severe muscle weakness. Serum creatine kinase may be slightly elevated.
Late adult onset myopathy with onset in legs (autosomal dominant): muscle weakness usually appears after the age of 35 and is confined to the lower legs, especially the tibialis anterior. EMG and histopathology are myopathic. Serum creatine kinase may be slightly elevated.
Early adult onset myopathy with onset in posterior compartment of lower legs (autosomal recessive): initial symptoms include difficulty climbing stairs or running. Weakness is most pronounced in the gastrocnemius muscle. EMG is myopathic. CT or MRI show pronounced lesions in the posterior compartment of lower legs. Muscle biopsy shows severe myopthic changes in proximal muscles. Serum CK is elevated 10- to 100-fold.
Early adult onset myopathy with onset in anterior compartment of lower legs: initial muscle weakness is accompanied by foot drop. As disease progresses, posterior compartment muscles may become involved, but intrinsic foot muscles are spared. Serum CK is only mildly elevated.
Other forms: selective weakness of toes and flexors before the age of 25, progresssing to finger extensors; adult onset myopathy associated with desmin storage and autophagocytosis.
Differential Diagnosis: involvement of proximal, facial, or trunk muscles is not clinically significant, except for an extremely rare form of adult onset distal myopathy associated with desmin storage. Presence of central cores, inclusion bodies, nemaline bodies, or lipid or glycogen accumulations excludes a diagnosis of distal myopathy.
See Diagnostic Criteria for Neuromuscular Diseases http://www.enmc.org/nmd/diagnostic.html.
| | Treatment Notes | Late adult onset myopathy with onset in hands is the most common form. Patients sometimes complain of coldness of hands and feet, but sensation is normal.
Progression: Most forms are slowly progressive, and not life-threatening. The clinical course of the extremely rare form associated with desmin storage is variable, but may be rapid, progressing to include bulbar, respiratory, and facial muscles, and cardiomyopathy with conduction defects. | | Protein ID | 25 | | Gene Location | varies with subtype | | Abstract | Disease subtypes: Tibial muscular dystrophy; Myoshi myopathy.
Welander's late adult onset myopathy with onset in hands is the most common form of distal myopathy. Initial symptoms include clumsiness with precise hand movements and difficulty with extension of the fingers. Distal leg muscle weakness develops over time, making it difficult to walk.
Several forms of distal myopathy have been identified, and inheritance may be either autosomal dominant or autosomal recessive. Autosomal dominant inheritance means that one affected parent (mother or father) has a 50% chance of passing the trait to a child; both sons and daughters are equally likely to be affected. Two affected people can have an unaffected child. Although it is likely that an affected person has an affected parent, there are exceptions: the affected person is the result of a new mutation; the parent transmitting the gene is an asymptomatic carrier; or the parent of the affected individual expressed the gene but in ways that were not readily recognized.
Autosomal recessive inheritance requires that both the mother and father have at least one copy of an altered gene located on one of the 22 autosomes (that is, not the X or Y chromosomes). These parents may be carriers who show no signs of the disease (i.e., each has one copy of an altered gene), but they have a 25% chance of producing either a normal child or a child with the disease; they have a 50% chance of producing offspring who are carriers with no signs of disease. Two affected parents (i.e., each has two copies of an altered gene) usually produce children who are all affected. Males and females are at equal risk for being affected.
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