Chronic progressive
external ophthalmoplegia (CPEO) is a disorder characterized
by slowly progressive paralysis of the extraocular
muscles. Patients usually experience bilateral, symmetrical,
progressive ptosis, followed by ophthalmoparesis months
to years later. Ciliary and iris muscles are not involved.
CPEO is the most frequent manifestation of mitochondrial
myopathies. CPEO in association with mutations in
mitochondrial DNA (mtDNA) may occur in the absence
of any other clinical sign, but usually it is associated
with skeletal muscle weakness. Kearns-Sayre syndrome
(KSS) is a related mitochondrial myopathy that demonstrates
the following: CPEO, onset before age 20, and pigmentary
retinopathy. KSS also has at least one of the following:
cardiac conduction defects, cerebrospinal fluid (CSF),
protein of greater than 100 mg/dL, and a cerebellar
syndrome. Other abnormalities in KSS can include mental
retardation, Babinski sign, hearing loss, seizures,
short stature, delayed puberty, and various endocrine
disorders. CPEO also can be a sign in the following
disorders: oculopharyngeal dystrophy, myasthenia gravis,
and Graves disease.