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CMD Overview
The congenital muscular dystrophies represent a group of diseases causing muscle weakness at birth. Several defined genetic mutations cause muscles to break down faster than they can repair or grow. A person with CMD may have various neurological or physical impairments. Some never gain the ability to walk, while others lose the ability as they grow older.
Video: Overview of Congenital Muscular Dystrophy by Dr. Jim Collins
Congenital Muscular Dystrophy Subtypes
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Collagen VI (Ullrich CMD, Intermediate COL6, Bethlem Myopathy)
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alpha-Dystroglycanopathy (Walker-Warburg, Fukuyama, Muscle-Eye-Brain, LGMD2I, LGMD2K, LGMD2M, LGMD2N, LGMD2O)
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LAMA2 (Merosin Deficient, Merosin Negative)
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SELENON/SEPN1 (Rigid Spine MD, Multi-Minicore Disease)
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LMNA (L-CMD, Laminopathy, Emery-Dreifuss MD)
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Other (Alpha Integrin, Choline Kinase, SYNE1, TCAP, Titan, RYR1, Undiagnosed CMD)
Video: Genetic Diagnoses of CMD by Sandra Donkervoort, MS, CGC
The Physiology of Muscular Dystrophy
The CMDs involve proteins in four locations of the muscle cell. Mutations in any of these proteins account for some form of muscular dystrophy.
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The extracellular matrix proteins (collagen, laminin, integrin alpha 7 and 9)
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the glycosyltransferase proteins: proteins that place a sugar on the alpha dystroglycan (dystroglycanopathies or glycosyltransferase deficiencies)
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intracellular protein deficiency (selenoprotein)
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intranuclear intermediate filament deficiency (lamin A/C and nesprin 1)
Prevalence of Congenital Muscular Dystrophy
Due to barriers in diagnosis, it is still difficult to calculate the prevalence of CMD. A study out of Italy (Prevalence of congenital muscular dystrophy in Italy: A population study. Graziano A1, Bianco F1, et.al., Neurology. 2015 Mar 3;84(9):904-11) suggests an estimated prevalence of 1 in 100,000 births. This is a gross estimate and true prevalence will not be well understood for many years to come.
