Distrofias musculares congénitas

Congenital muscular dystrophies (CMDs) are inherited muscle disorders with a high clinical and genetic heterogeneity. Diagnostic criteria are histological (dystrophy in muscle biopsy) and clinical (onset at birth or before the age of walking). Affected infants typically appear “floppy” with low muscle tone and poor spontaneous movements. Patients may present with delay or arrest of gross motor development. CMDs show progressive weakness, joint contractures, spinal stiffness and deformities, respiratory compromise and certain types may develop cardiac symptoms. Multidisciplinary management is required, including neuro-orthopedic, cardio-respiratory and often surgical treatment. Dosage of muscle enzymes (CK) helps in the diagnostic pathway. Marked increase is observed in merosin deficient CMD (LAMA2 gene) and in the dystroglycanopathies, which are genetically very heterogeneous. Both disorders may show central nervous system abnormalities, being often associated with mental retardation in dystroglycanopathies, while merosinopathies show only striking white matter changes and intellect is not impaired. Muscle biopsy helps to detect defects in merosin expression or abnormal dystroglycane glycosylation. CMDs without marked increase of CK do not associate brain involvement. Diagnosis is often oriented by the identification of clinical markers such as distal hyperlaxity in Ullrich CMD (COL6 genes), selective spinal rigidity and respiratory failure in selenopathies (SEPN1 gene), or dropped head in laminopathies (LMNA gene). Muscle MRI is very useful to confirm clinical suspicion and orientate difficult cases. Gene identification in these disorders and development of animal models are helping to better understand their physiopathologic mechanisms, opening the possibility for future therapies.