What Is CMT-CRYAB?
CMT-CRYAB is a type of CMT caused by autosomal dominant mutations in the CRYAB gene. This gene provides instructions for making alpha-B-crystallin, a small heat-shock protein that acts as a molecular chaperone, helping other proteins fold correctly and protecting cells, including nerve and muscle cells, from stress. Mutations in the CRYAB gene disrupt this chaperone function, leading to impaired nerve signal transmission.
CMT-CRYAB is autosomal dominant, meaning that just one of the gene’s two copies needs a mutation to cause this subtype.
Clinical Features
CMT-CRYAB has a late onset, typically after age 40. Nerve conduction studies usually show somewhat slowed conduction velocities and reduced amplitudes, consistent with an axonal form of CMT.
CMT-CRYAB symptoms may include:
- Distal weakness in the feet and lower legs, developing after age 40
- Reduced sensation in the hands and feet
- Muscle atrophy
- Foot drop
- Reduced or absent reflexes
- Congenital cataracts
- Breathing muscle weakness is common
- Additional symptoms not listed here
Disease Course
CMT-CRYAB is slowly progressive following its late onset. Regular cardiac and respiratory monitoring is recommended for affected individuals with this subtype.
