KSS is a multiorgan disease characterized by the clinical triad of a chronic,
progressive, external ophthalmoplegia, retinal pigment degeneration (with progressive
loss of vision), and onset before the age of 20 years. Significant other clinical findings
may include increased levels of protein in the cerebrospinal fluid, dementia,
encephalopathy, cerebellar ataxia, bulbar weakness (dysphagia, which may also be related
to cricopharyngeal achalasia), electroencephalographic anomalies (including seizures),
sensorineural hearing loss, corneal anomalies (with increased risk of spontaneous
perforation), but also cardiac anomalies (e.g., high-degree atrioventricular heart blocks,
QT prolongation with the risk of sudden death, dilated cardiomyopathy, mitral valve
prolapse, congestive heart failure), endocrine anomalies (hypogonadism, short stature due
to growth hormone deficiency, hyperaldosteronism, diabetes mellitus, hypoparathyroidism,
hypothyroidism), renal tubular acidosis, and myopathy with weakness. The clinical spectrum
is related to the proportion of normal and mutant DNA.