congenital muscular dystrophy : an overview

congenital muscular dystrophy (cmd)  is an umbrella term collecting a heterogeneous groups of genetic disorders , mostly with autosomal recessive mode of inheritance , and are characterized by muscle weakness since birth or in early infancy , with a dystrophic pattern on muscle biopsy . these children are usually hypotonic and may have joint contractures . the serum creatine kinase level can be elevated. the clinical course is usually static, but occasionally slow regression and sometimes a relative improvement can be noticed . a dozen number of genes are known to cause congenital muscular dystrophy and many individuals with cmd remain unclassified . cmd can be subdivided based on the expression of the extracellular matrix protein , laminin-alpha2 (merosin) on muscle biopsy ,  into merosin negative and positive . some clinical features are crucial for making more accurate diagnosis such as distal laxity (common in collagen 6 disorders) and rigid spine (seen in selenopathies) .