Limb-girdle muscular dystrophy subtypes: First-reported cohort from northeastern China

Area of Science:

• Neurology
• Genetics
• Biochemistry

Background:

• Limb-girdle muscular dystrophies (LGMDs) are a heterogeneous group of genetic disorders affecting skeletal muscles.
• The prevalence of specific LGMD subtypes varies significantly across different ethnic and geographic populations.
• Understanding subtype distribution is crucial for accurate diagnosis and genetic counseling.

Purpose of the Study:

• To determine the relative frequencies of different limb-girdle muscular dystrophy subtypes in the Chinese Han population.
• To compare the clinicopathological features of LGMD subtypes in this cohort with existing literature.
• To establish the first report on LGMD subtype proportions in China based on protein analysis.

Main Methods:

• Retrospective analysis of 68 patients diagnosed with limb-girdle muscular dystrophy at a single center in China.
• Biochemical and immunohistochemical analysis of muscle biopsies to identify specific protein deficiencies (e.g., calpain-3, dysferlin, alpha-sarcoglycan, caveolin-3).
• Histopathological examination of muscle biopsies to assess features like rimmed vacuoles, inflammatory infiltrates, and fiber types.

Main Results:

• Calpainopathy (LGMD2A) was diagnosed in 17% of patients, and dysferlin deficiency (LGMD2B) in 15%.
• Alpha-sarcoglycan deficiency (LGMD2D) and caveolin-3 deficiency were identified in 3% each.
• A significant proportion (62%) were classified as unclassified LGMD; distinct histological features differentiated calpainopathy and dysferlinopathy.

Conclusions:

• The distribution of LGMD subtypes in the Chinese Han population is broadly similar to Western populations.
• Calpainopathy presents as a more chronic, less active disease compared to dysferlinopathy.
• This study provides essential data on LGMD epidemiology in China and highlights the diagnostic utility of specific stains like acid phosphatase for dysferlinopathies.