Last month’s case presented a 32-year-old man with ptosis since childhood and visual impairment since the age of 29. Examination (Watch the video now at PracticalNeurology.com) revealed fixed ophthalmoplegia and bilateral ptosis. Muscle biopsy showed many ragged red fibers.
The most appropriate next step is to look for:
1. A large mitochondrial deletion in muscle tissue.
2. A large mitochondrial deletion in the while blood cells.
3. A deletion in nuclear mitochondrial genes such as POLG.
4. A point mutation in the mitochondrial genome.
5. Twinkle gene mutations in ocular muscles.
The correct answer is 1. The age of onset, the chronicity of symptoms, the cardiac conduction abnormalities, and retinal pigmentary changes are all consistent with Kerans-Syare syndrome.
• Kearns-Sayre syndrome is a multisystemic disease mainly affecting the muscles, eyes, and heart. It is usually caused by spontaneous mutation. In some cases it can be inherited via mitochondrial, autosomal dominant or autosomal recessive modes.
• Symptoms usually appear before the age of 20 years.
• KSS is an important cause of progressive ophthalmoplegia without pupillary involvement, non-fluctuating ptosis, progressive loss of vision due to retinitis pigmentosa, cardiac conduction defect, and sometimes ataxia. CSF protein is usually elevated.
• Proximal weakness, facial weakness, deafness, dementia, seizures, and diabetes mellitus also occur in some patients which emphasizes the widespread nature of this mitochondrial disease.
• Prevalence is 2:100,000 individuals
• Single large deletion ranging from 1,000 to 10,0000 nucleotides is usually detected.
• KSS is a progressive disorder. Heart block can cause death in 20% of cases. Early pacemaker implantation prolongs life expectancy.
• Gomori Trichrome stain of skeletal muscle usually shows higher concentration of mutated mitochondria in some fibers that accumulates in the periphery of the muscle fibers (ragged red fibers).
• No treatment is available. Blepharoplasty is indicated for severe ptosis.