inclusion body myopathy 2
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Epidemiology
- mean age of onset 20-35 years
Pathology
- rimmed vacuole myopathy, no inflammation
- degenerating muscle fibers with abnormal accumulations of beta-amyloid protein
- no central nervous system disease
Genetics
- autosomal recessive
- defect in GNE gene
Clinical manifestations
- proximal & distal muscle weakness, gait difficulties
- progressive wasting of the upper & lower limbs, progression gradual
- severe incapacitation within 10-20 years
- muscles of the shoulder girdle severely affected in advanced cases, with relative sparing of deltoid, biceps, & triceps
- sparing of the quadriceps muscles even in advanced stages of disease
- ocular, pharyngeal, & cardiac muscles not involved
Laboratory
- serum creatine kinase normal or slightly elevated