What Is CMT-SARS1?
CMT-SARS1 is a type of CMT caused by autosomal dominant mutations in the SARS1 gene. This gene provides instructions for making seryl-tRNA synthetase, an enzyme that attaches the amino acid serine to its transfer RNA during protein synthesis. Mutations in the SARS1 gene disrupt this function, leading to impaired nerve signal transmission.
CMT-SARS1 is autosomal dominant, meaning that just one of the gene’s two copies needs a mutation to cause this subtype.
Clinical Features
The age of symptom onset in CMT-SARS1 is variable, ranging from childhood to adulthood. Symptoms typically begin in the lower extremities and progress over time to involve the upper limbs. Nerve conduction studies usually show slowed conduction velocities, consistent with a demyelinating form of CMT.
CMT-SARS1 symptoms may include:
- Weakness in the feet and lower legs
- Muscle atrophy
- Foot drop
- Reduced or absent reflexes
- Reduced sensation
- A steppage-style walking pattern
- Foot deformities, including high arches, and hammertoes (clawed toes)
- Progressive involvement of the hands and forearms
- Difficulty with fine motor skills and manual dexterity
- Additional symptoms not listed here
Disease Course
CMT-SARS1 shows wide variability in severity and progression. Some individuals are mildly affected, while others develop a more severe disease. Disease progression is generally slow, and life expectancy is not reduced.
