Diagnostic Significance of Immunohistochemical Staining in Muscular Dystrophy

Kim, Dae Seong

Abstract

Muscular dystrophy (MD) is a heterogeneous group of inherited muscle disorders caused by the mutations of different genes encoding muscle proteins, and it is now classified according to the results of the linkage analysis and the genes or proteins affected. Except for some subtypes of MD presenting with characteristic manifestations, differential diagnosis is always a challenging task to clinicians because of the similarities in clinical features and muscle pathology findings between subtypes. The immunohistochemical stain (IHC) using a biopsied skeletal muscle is an effective and simplest way to identify defective proteins in MD, so that we can classify MD into its subtypes and target the affected gene. The frozen muscle sections are used for the IHC, and specialized procedures of fixation, blocking, antibody reaction, and detection are serially performed. By using sets of commercially available antibodies, we can identify many different subtypes of MD, which include dystrophinopathies, several forms of limb-girdle muscular dystrophies, and subgroups of congenital muscular dystrophies. Although each disease shows its own characteristic patterns on IHC, there are some exceptional cases including normal expression of the mutated protein and secondary loss of the unaffected protein. Since the quality of the IHC results largely depends on technique and experience, the choice of antibody panel for IHC should be individualized in each laboratory considering the number of muscle biopsy requests, available technicians, and expenses for the study.