What Is CMT-COA7?
CMT-COA7 is a type of CMT caused by autosomal recessive mutations in the COA7 gene. This gene provides instructions for making a protein required for assembling cytochrome c oxidase, the final enzyme complex in the mitochondrial respiratory chain, which is essential for producing cellular energy in nerve and muscle tissue. Mutations in the COA7 gene impair this assembly process, disrupting mitochondrial energy production in peripheral nerves and the cerebellum.
CMT-COA7 is autosomal recessive, meaning that both copies of the gene must have a mutation to cause this subtype.
Clinical Features
The age of symptom onset in CMT-COA7 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 somewhat slowed conduction velocities and reduced amplitudes, consistent with an axonal form of CMT.
CMT-COA7 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-COA7 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.
