Limb girdle muscular dystrophy: weakness and disease duration as predictors of functional impairment.

This cross-sectional study compared progressive weakness to functional disability in 20 patients with limb girdle muscular dystrophy. Weakness (assessed by manual muscle testing) determined disability (assessed by functional grades, timed functional tests, and an activities of daily living scale). For any functional grade the degree of weakness varied between patients. Yet, at a certain "threshold" weakness the functional level predictably deteriorated. Change in functional grade did not reflect a parallel increase in weakness nor disease progression. Functional "milestones" were reached at varying durations of disease. Only guidelines were offered to individual patients as to the time course of progression in disability. Serial timed tests should be a sensitive, objective method to follow the rate of disease progression. Timely referral of patients to establish physical needs should delay functional deterioration and minimize handicap despite progressive weakness.