Kearns–Sayre Syndrome

Kearns–Sayre syndrome is a mitochondrial disorder characterized by progressive external ophthalmoplegia, pigmentary retinopathy, and onset before age 20. Additional features may include cardiac conduction defects, cerebellar ataxia, and endocrine abnormalities. Pathophysiology involves mitochondrial DNA deletions impairing oxidative phosphorylation. Diagnosis relies on clinical criteria, muscle biopsy, and genetic testing. Management is supportive, including cardiac pacing, ophthalmologic care, and mitochondrial therapy; prognosis is variable depending on systemic involvement.