Diagnostic Methods And Clinical Features Of Chinese LGMD2A Patients

ObjectiveLimb-girdle muscular dystrophy (LGMD) is a group of heterogeneous muscular disorders, characterized by progressive proximal muscle weakness and atrophy of bilateral limbs. According to the pattern of inheritance, it could be divided into two major subtypes, autosomal dominant (LGMD 1) and autosomal recessive (LGMD 2) types comprising 21 different entities in sum. For a great part of the world, the most prevalent form is LGMD2A, manifesting proximal muscular weakness and serum creatine kinase makedly elevation in teenage years accompanied by consanguineous pedigrees. It is difficult to identify the disease on the basis of clinical symptoms. The diagnosis still depends on molecular data or protein analysis.Limb-girdle muscular dystrophy type 2A (LGMD2A) is a muscular disorder originated by the deficiency of Ca2+ dependent neutral cystein protease, calpain-3. Up to now, relating data was absent in Chinese population. The responsible mutated gene, CAPN3, was located in 15q15.1-q21.1. It is a relatively large gene comprising 24 exons without any hot spot, resulting in laborious and costly molecular analysis. Calpain-3, skeletal muscle specific, distributed too unarranged intracytoplasma to be analyzed during immunohistochemical study. However, the diagnosis of LGMD2A could be established by semi-quantitative analysis using Western blot analysis. Furthermore, the clinical and pathological aspects would also be reviewed in the study to portray Chinese LGMD2A.In order to achieve the clinical and pathological features of Chinese LGMD2A, firstly we selected a total of 93 samples from our muscle biopsy database (2006-2009) following the criteria for further immunohistochemical staining. Combined Western blotting with dysferlin and calpain-3 antibodies were employed so as to detect target proteins expression. Among 93 cases enrolled,18 patients showed either absence (13 cases) or severely reduction (5 cases) of calpain-3 as well as intacted or slightly reduced dysferlin expression. For this reason, they were diagnosed as calpainopathy (LGMD2A) at protein level. Another 36 cases were identified dysferlinoapthy, because they showed either absence (31 cases) or severely reduction (5 cases) of dysferlin as well as intacted or slightly reduced calpain-3.According to combined Western blotting results, LGMD2A possibly accounts for 29% and LGMD2B accounts for 47.6% of Chinese LGMD patients. In a retrospect of 18 LGMD2A patients (Male:Female = 1:1), the mean onset age was 18.8. As for clinical aspects, muscle strength worsened in hip extension, which matches the selective involvement revealed by muscle MRI study. Further,14 cases (77.8%) accompanied by bilateral winging scapulaes (12 symmetrical and 2 asymmetrical). Achilles tendon contractures were also found in 12 cases (66.7%),1 patient among which had bilateral elbow contractures. All 18 LGMD2A patients showed muscular dystrophy pattern in pathological study, in which 12 cases (66.7%) had lobulated fibres and 8 cases (55.6%) had whirled fibres.Our research is the first trial to employ combined Western blot analysis in diagnosing LGMD2A and LGMD2B in Chinese population and advantages of Western blot were also discussed compared with other diagnosing implements. We attempted to portray the clinical and pathological features of Chinese LGMD2A cases, expecting to offer some clues for clinical practice.