Dystrophin analysis in the diagnosis of childhood muscular dystrophy: an immunohistochemical study of 75 cases.

Seventy-five consecutive pediatric muscular dystrophy (MD) cases were analyzed by dystrophin immunohistochemistry (75/75), Western blot analysis (26/75), DNA analysis (30/75), and immune electron microscopy (8/75). The patients included 64 males and 11 females and the clinical diagnoses were Duchenne MD (DMD) (41), Becker MD (BMD) (8), intermediate/outlier MD (4), female DMD (3), limb girdle or Becker (1), congenital MD (CMD) (10), Fukuyama CMD (1), facioscapulohumeral MD (FSH) (3), limb girdle MD (2), and other uncharacterized dystrophies (2). Dystrophin analysis was performed on all cases using the N- and C-terminal antidystrophin antibodies. Dystrophin analysis helped to exclude an Xp21 dystrophy in four patients. Except for two patients who showed normal staining with the N-terminal and abnormal staining with the C-terminal antibody, all DMD cases showed absent staining except for the immunoreactive revertant fibers, which were generally under 5%. A variety of staining patterns was seen in BMD, ranging from normal to abnormal (variable intensity of staining, partially stained/unstained fibers). Abnormalities were observed with the C-terminal antibody in one case of CMD and Fukuyama CMD, and normal staining was present in the other dystrophies. Immune electron microscopy confirmed absence of staining in DMD and normal membrane staining in other dystrophies. Our study underscores the importance of using antibodies with specificities to different regions of the dystrophin molecule for accurate diagnosis. As abnormal staining may be encountered in non-Xp21 dystrophies such as CMD, dystrophin staining should not be used in isolation to make a diagnosis of a dystrophinopathy.