Congenital muscular dystrophy
Autosomal recessive muscle diseases with weakness present at birth.
Congenital muscular dystrophies are a group of autosomal recessively-inherited muscle diseases characterized by muscle weakness present at birth. They are heterogeneous disorders with muscle biopsy changes ranging from myopathic to overtly dystrophic depending on the age at biopsy.
Quick Facts
- Symptoms
- Muscle weakness
- Types
- 17 types of CMD
- Diagnosis
- NRI, EMG
- Treatment
- Currently there's no cure; one should monitor cardiac function and respiratory function
Facts from the source article.
Signs and symptoms
Most infants with CMD display progressive muscle weakness or atrophy, though severity varies. Hypotonia, or lack of muscle tone, makes infants appear unstable. Many eventually develop joint contractures or fixed deformities. Children may be slow to achieve motor milestones such as rolling over, sitting up, or walking, and some rarer forms can cause significant learning disabilities.
Genetics
CMDs are autosomal recessively inherited, except in some de novo mutations and Ullrich CMD. In most cases both parents must be carriers. The disorders are heterogeneous, with 35 genes identified. One group involves defects in extracellular matrix genes. Merosin-deficient CMD (MDC1A), about one-third of cases, results from LAMA2 gene mutations on chromosome 6q2, encoding laminin-α2 chain; most patients lack laminin-α2 in muscle. Ullrich CMD is caused by mutations in COL6A1, COL6A2, or COL6A3, encoding collagen VI alpha chains. It can be autosomal recessive or dominant (dominant usually de novo); recessive mutations often cause complete absence of collagen VI. Rigid spine CMD (RSMD1) results from SELENON gene mutations encoding selenoprotein N, expressed in rough endoplasmic reticulum of skeletal muscle, heart, brain, lung, placenta, and at high levels in diaphragm. RSMD1 is rare but SEPN1 mutations also occur in other congenital myopathies.
Diagnosis
Muscle fibrosis and joint contractures or fixed deformities are cardinal clinical signs, though some patients initially present with joint laxity. Severe deformities can cause joint dislocation and gait abnormalities. Subtype-specific patterns of muscle and joint involvement, especially for MDC1A, can aid differential diagnosis but must be correlated with other clinical signs, neuro-imaging, muscle biopsy immunostaining, and genetic analysis. Cardiac manifestations vary from absent to severe, including dilated cardiomyopathy, systolic dysfunction, hypertrophic cardiomyopathy, myocardial fibrosis, or fatal ventricular arrhythmias. Dystroglycanopathies like Fukuyama CMD have high likelihood of significant cardiac involvement; MDC1A cardiac manifestations are usually asymptomatic. Cardiac examination and surveillance are important. Diagnostic tests include CK levels, muscle MRI (especially whole-body MRI for laminin-α2 deficiency), EMG, and genetic testing.
Management
The American Academy of Neurology recommends monitoring cardiac, respiratory, and gastrointestinal function. Speech, orthopedic, and physical therapy may improve quality of life. There is no cure, but preserving muscle activity and correcting skeletal abnormalities such as scoliosis is important. Orthopedic procedures like spinal fusion can maintain or increase physical movement.
Frequently Asked Questions
How is Congenital muscular dystrophy treated?
Treatment of Congenital muscular dystrophy includes currently there's no cure and one should monitor cardiac function and respiratory function.
How is Congenital muscular dystrophy diagnosed?
Diagnosis of Congenital muscular dystrophy is based on NRI and EMG.
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