Limb girdle muscular dystrophy: description of a phenotype

Hip abduction sign: a new clinical sign in sarcoglycanopathies

A new clinical sign in sarcoglycanopathies is described. Patients with sarcoglycanopathies showed a phase of abduction of the thighs while rising from the ground: the hip abduction sign. The sign results from selective weakness of hip adductors and comparative preservation of hip abductors. This sign had a sensitivity of 76.2%, specificity of 98%, and was most conspicuous between 3 and 10 years of disease duration. The hip abduction sign is an important clinical indicator of sarcoglycanopathies.

Limb girdle muscular dystrophy: an interval study of weakness and functional impairment

OBJECTIVE

Prospective studies of the natural history of a myopathy are effective means of measuring the status and progression of disease. This 10-year interval study of progressive weakness and functional decline was aimed to document the natural course of clinically well-characterized limb girdle muscular dystrophy in South Africa.

METHODS

The manual muscle test (MMT) was used to evaluate limb strength; global strength was measured by the average muscle score (AMS). A nonlinear functional grading system was used to measure impairment of the arms and legs. An activities of daily living (ADL) scale was used to assess disability across multiple functional domains in a home environment.

RESULTS

The mean AMS deteriorated from 5.9 to 4.9 (on a 10-point scale) and was unrelated to patient age and disease duration. Most (78%) patients lost arm function. All patients maintained useful hand function. Two thirds of patients lost leg function. Half of the patients were wheelchair bound, and they reached this level of function around the end of their fourth decade of life. Every patient showed functional deterioration on the ADL scale. The mean score worsened from 65.6 to 77.2 (out of 156 points). The disability change was most pronounced in patients who became wheelchair bound.

CONCLUSION

This interval analysis showed a significant decline of limb strength that was independent of patient age or duration of disease and was more rapid in stronger patients. A functional grading system detected decline and was a useful measure of deterioration when applied to patients over intervals. An ADL assessment ascertained a significant functional decline across multiple functional domains in a home environment and allowed us to advise patients on compensatory strategies to limit dependence.

Calpains in muscle wasting

Calpains are intracellular nonlysosomal Ca(2+)-regulated cysteine proteases. They mediate regulatory cleavages of specific substrates in a large number of processes during the differentiation, life and death of the cell. The purpose of this review is to synthesize our current understanding of the participation of calpains in muscle atrophy. Muscle tissue expresses mainly three different calpains: the ubiquitous calpains and calpain 3. The participation of the ubiquitous calpains in the initial degradation of myofibrillar proteins occurring in muscle atrophy as well as in the necrosis process accompanying muscular dystrophies has been well characterized. Inactivating mutations in the calpain 3 gene are responsible for limb-girdle muscular dystrophy type 2A and calpain 3 has been found to be downregulated in different atrophic situations, suggesting that it has to be absent for the atrophy to occur. The fact that similar regulations of calpain activities occur during exercise as well as in atrophy led us to propose that the calpains control cytoskeletal modifications needed for muscle plasticity.

Limb girdle muscular dystrophy: a prospective follow-up study of functional impairment

This 6-year prospective follow-up study evaluated the rate of clinical disease progression in 19 of 20 previously reported patients with strictly selected limb girdle muscular dystrophy. There was no significant deterioration in muscle strength (assessed by manual muscle testing). An activities of daily living (ADL) scale showed significant functional deterioration in 30% of patients with predominant involvement in a single functional domain variable between patients, and determined by the patient's previous level of function. A functional grading system showed that 70% of patients had deteriorated at least one grade in the arms and/or legs. Deterioration of the ADL score correlated with the loss of functional grades. We conclude that assessment of functional ability may be more sensitive to detect clinical disease progression compared to testing of muscle strength. The clinical parameter that correlates best with the activity of the underlying disease process is not determined. Tests for strength and functional impairment are complementary. Patients expressed appreciation that functional disability was addressed during follow-up visits.