Kearns–Sayre syndrome

Kearns–Sayre syndrome (KSS) is a severe mitochondrial myopathy caused by genetic defects in mitochondrial DNA, characterized by early onset (before age 20) and symptoms such as progressive external ophthalmoplegia, pigmentary retinopathy, cardiac conduction abnormalities, muscle weakness, and multiple systemic issues including cognitive impairments, cerebellar ataxia, and various endocrinopathies. The condition progressively affects muscles bilaterally and involves significant energy production impairments at the cellular level.