The role of immunocytochemistry in congenital myopathies.

Immunocytochemistry is playing an increasingly important role in the field of congenital myopathies. It is not yet the diagnostic tool that it is for the muscular dystrophies, but nevertheless it provides useful information on the nature of the structural defects that define each congenital myopathy, and on the additional secondary changes that accompany them. Immunocytochemistry may have a role in identifying primary protein defects but this may be dependent on the effect of a mutation on protein expression. Mutations affecting function, rather than expression, of a protein may not be detected by immunocytochemistry. Studies of candidate proteins, such as nebulin in nemaline myopathy, and the ryanodine receptor in central core disease, are, however, in progress, and as more defective genes are identified, and antibodies become available, immunocytochemistry will have an increasingly important role. Myofibrillar components are frequently affected in congenital myopathies and immunocytochemical localisation of their isoforms can reveal the nature of the structural abnormalities, such as rods, cores, and a variety of inclusions. Developmentally regulated proteins such as myosin heavy chains and intermediate filaments are also relevant to the understanding of the maturational process, in particular in myotubular/centronuclear myopathies, and also to the plasticity of muscle fibre types. Immunocytochemistry will continue to play an active role in studies of congenital myopathies and provide insight into their pathogenesis.