[Diagnostic methodology in muscular pathologies]. / Metodología diagnóstica en la patología muscular.

AIMS: To analyse the different methodologies and their technical approaches, and compare the value and specificity of each of them in the diagnostic interpretation of muscular biopsies. DEVELOPMENT: Since the first descriptions by Duchenne in the 19th century, a series of stages for interpreting muscular biopsies crucial to the methodological approach were developed. The largest groups of muscular diseases (neurogenic atrophy, dystrophy and others), which were established on the basis of purely morphological studies, were later examined using histochemical techniques that allowed some diseases to be considered on an individual basis. One decisive factor in interpreting muscular biopsies and in diagnostic accuracy was the application of immunohistochemical techniques. The discovery of the gene responsible for Duchenne and Becker muscular dystrophies, and the later identification of dystrophin using reverse genetics, triggered off a series of events which led to the identification of various genes and proteins responsible for a number of muscular diseases. From that moment onwards it became possible to distinguish between previously undefined muscular dystrophies, e.g. different types of limb girdle dystrophy, to subclassify allelic diseases, such as Becker muscular dystrophy, and to identify carriers of X-linked diseases, for example. Ultrastructural examinations have also proved to be very useful. CONCLUSION: At present, the degree of diagnostic accuracy achieved in muscular pathologies is remarkable and the discoveries that have gradually been made have marked a series of stages, none of which has excluded the one preceding it and all of which are of great importance when it comes to interpreting a muscular biopsy.

[Gamma-sarcoglycanopathy: clinico-pathological and genetic study of 11 cases]. / Gamma-sarcoglicanopatía: estudio clinicopatológico y genético de 11 casos.

INTRODUCTION: Limb Girdle Muscular Dystrophy type 2C (LGMD2C) is an autosomal recessive dystrophy due to the deficit of gamma-sarcoglycan, one of the proteins of the dystrophin-associated proteins complex (DAP). A new mutation in the gamma-sarcoglycan gene, 13q12, has been described recently and is exclusive of the gypsy community. OBJECTIVE: To describe the clinicopathological and the genetic findings of eleven cases from a Spanish gypsy family with LGMD2C and the mutation C283Y. MATERIAL AND METHODS: We describe a large gypsy family with the C283Y mutation and eleven affected patients. We have performed an extensive clinical and pathological study with immunohistochemistry and Western blot analyses in the eleven patients and a genetic study of a total of twenty-seven members of the family. RESULTS: The patients presented a severe muscular dystrophy with a dystrophic pattern in the muscle biopsy, normal immunolabeling for dystrophin, very weak for alpha-, beta- and delta-sarcoglycan and absent for gamma-sarcoglycan. These eleven patients were found to be homozygous for the mutation and twelve other members of the family, heterozygous. CONCLUSIONS: The clinical picture and the evolution of the disease herein described is similar to that observed in DMD. Two fundamental differences were found: the autosomal recessive mode of inheritance, and the normal immunohistochemistry and immunoblot for dystrophin in the skeletal muscle.

[Dystrophinopathies, congenital muscular dystrophy, limb-girdle dystrophies: updated classification]. / Distrofinopatías, distrofia muscular congénita y distrofias de cinturas: clasificación actualizada.

OBJECTIVES: To review the up-dated classification of limb girdle muscular dystrophies (LGMDs) in relation to the defective protein and the genetic abnormality. To explain how these proteins are related to dystrophin and to the proteins of the extracellular matrix. To show that an accurate diagnosis is necessary and that it can be adequately made in neuromuscular pathology laboratories. DEVELOPMENT: We present a study of the different types of LGMDs, dystrophinopathies and congenital muscular dystrophy. We emphasize the recent events which concluded in the identification of these disorders, the genetic alteration, the defective proteins and, briefly, the clinical features. CONCLUSIONS: The recent identification of numerous skeletal muscle proteins and of the codifying genes made possible a new classification of a large group of muscular dystrophies. The possibility to study these proteins on the muscle biopsy with immunohistochemistry and Western blot techniques indicates the need of an accurate diagnosis in specialized neuromuscular laboratories. Since there is a great number of genes discovered and of mutations within the same gene, and the clinical picture of different diseases can be similar, a previous study of the protein is advisable as a guide for a further genetic study.