This recently reported heritable disorder involves the nervous system. It is caused by mutations located in cellular organelles called mitochondria. These are 'energy factories' that contain DNA which may mutate similar to that of DNA located in the nucleus.
The first symptoms appear in young adulthood when difficulty walking becomes apparent. The gait may be broad-based and unsteady (ataxia). Speech may be slurred and eye movements can be erratic (nystagmus). Some individuals have episodic attacks of increased difficulty moving with severe headache and nausea. Muscle tone and strength in the arms and legs are normal but ankle reflexes are sometimes decreased. Brain MRIs may reveal shrinkage of areas of the brain. Nerve conduction studies reveal involvement of peripheral nerves and patients may complain of numbness in the distal portions of the arms and legs
Some patients have mild cognitive difficulties.
A mutation in The DNA of mitochondria has been found in patients with this condition. Since mitochondria are only transmitted by females (sperm do not contain mitochondria), only the mother can transmit this disorder.
Clinical manifestations usually do not appear until adulthood. Neurologists and perhaps ophthalmologists may collaborate in the diagnosis and care.
There is very slow progression of symptoms in most individuals. Nothing is known regarding treatment and longevity.