congenital myopathies

congenital myopathies are a clinically and genetically heterogeneous group of inherited muscle disorders characterized clinically by reduced fetal movements, hypotonia, weakness and developmental delay beginning at birth or in the first year of life. however, there can be a wide variation in clinical findings including mild and asymptomatic presentation to a severe form within each subtype with childhood and adult onset. high arched palate, dysmorphic facies, scoliosis and joint contractures are usually present in infantile or childhood onset forms. intelligence is usually normal. prognosis is often determined by respiratory, orthopedic, and bulbar involvement. cardiac involvement is rare. the clinical course is usually non-progressive or slowly progressive. diagnosis and classification of a specific type of congenital myopathy depends on pathological findings on muscle biopsy including light microscopic and/or electron microscopic evaluation. type 1 fiber predominance and type 1 fiber hypotrophy are commonly seen features. the presence of characteristic structural abnormalities such as nemaline bodies, central cores and central nuclei, are the diagnostic hallmark of subtypes of congenital myopathies. structural and/or metabolic alterations during sarcomere formation and turnover can contribute to the clinical feature. there have been major advances in defining the genetic basis of the majority of congenital myopathy subtypes over the past decade. besides genetic heterogeneity in many of the congenital myopathies, mutations in the same gene can cause different pathologies. time, modifying genes, environmental factors and/or the site of the muscle biopsy may also influence the pathological appearance of the muscle. muscle pathology is still the mainstay of diagnosis and classification and guides molecular genetic testing. there are no curative treatments for congenital myopathies however a multidisciplinary approach including physical and occupational therapy orthopedic intervention, respiratory care and management of feeding difficulties are important goals of therapy.