Arthrogryposis spinal muscular atrophy
Overview
A group of inherited motor neuron diseases involving progressive muscle weakness and wasting due to degeneration of motor neurons in the spinal cord. Joint contractures are also present at birth.
Symptoms
- Joint contractures
- Muscle wasting in limbs
- Muscle weakness in limbs
- Muscle wasting in shoulders
- Muscle weakness in hips
- Curved spine
- Chest deformity
- Breathing problems
- Small jaw
- Droopy eyelids
Causes
Spinal muscular atrophies are genetic diseases. Types I, II, and III SMAs have been mapped to chromosome 5q11.2-13.3. In 1994, the survival motor neuron (SMN1) gene was identified as responsible for SMA when mutations occur.
Diagnosis
Diagnosis is based on the clinical presentation, family history, and genetic testing. The genetic test is based on the fact that approximately 95–98% of individuals with a clinical diagnosis of childhood SMA lack exon 7 in both copies of the SMN1 gene. Likewise, all patients with bulbospinal muscular atrophy have a defect in the androgen receptor gene.
Treatment
Treatment in severe childhood SMA includes prescription of antibiotics for respiratory infections and tube feeding in children with profound difficulty in sucking and swallowing. In children with SMA II, the goals of conservative therapy include maintaining the sitting posture, preserving or improving function, and reducing progression of deformity.