(1) The relative frequencies of the different forms of limb-girdle muscular dystrophy in China are similar to those reported in European countries. Calpainopathy is the most common form of limb-girdle muscular dystrophy in China, followed by dysferlinopathies. According to most cohorts studied to date, caveolinopathy appears to be a rare autosomal dominant form of limb-girdle muscular dystrophy, compared with other subtypes in China.Research Highlights
(2) Disease activity was associated with limb-girdle muscular dystrophy type 2B, while chronicity was associated with limb-girdle muscular dystrophy type 2A biopsies. Acid phosphatase staining is a powerful tool for detecting macrophage distribution in muscle biopsies. Cellular infiltrates are rare, but do not exclude limb-girdle muscular dystrophy type 2D, as is the case for rimmed vacuoles in dysferlinopathies.
The relative frequencies of different subtypes of limb-girdle muscular dystrophies vary widely among different populations. We estimated the percentage of limb-girdle muscular dystrophy subtypes in Chinese people based on 68 patients with limb-girdle muscular dystrophy from the Myology Clinic, Neurology Department, First Hospital of Jilin University, China. A diagnosis of calpainopathy was made in 12 cases (17%), and dysferlin deficiency in 10 cases (15%). Two biopsies revealed α-sarcoglycan deficiency (3%), and two others revealed a lack of caveolin-3 (3%). A diagnosis of unclassified limb-girdle muscular dystrophy was made in the remaining patients (62%). The appearances of calpain 3- and dysferlin-deficient biopsies were similar, though rimmed vacuoles were unique to dysferlinopathy, while inflammatory infiltrates were present in both these limb-girdle muscular dystrophy type 2D biopsies. Macrophages were detected in seven dysferlinopathy biopsies. The results of this study suggest that the distribution of limb-girdle muscular dystrophy subtypes in the Han Chinese population is similar to that reported in the West. The less necrotic, regenerating and inflammatory appearance of limb-girdle muscular dystrophy type 2A, but with more lobulated fibers, supports the idea that calpainopathy is a less active, but more chronic disease than dysferlinopathy. Unusual features indicated an extended limb-girdle muscular dystrophy disease spectrum. The use of acid phosphatase stain should be considered in suspected dysferlinopathies. To the best of our knowledge, this is the first report to define the relative proportions of the various forms of limb-girdle muscular dystrophy in China, based on protein testing.