The uneven distribution among tissue types is explained by mitochondrial heteroplasmy and the fact that a single cell can harbor both mutant and normal mtDNA. Skeletal and cardiac muscle are primarily affected, while other tissues that include cell types such as lymphocytes and fibroblasts are spared. KSS is usually caused by large deletions in mitochondrial DNA that span coding regions for subunits of complexes I, IV, and V of the electron transport chain, leading to faulty ATP production, oxidative stress, and eventual cell death. Systemic manifestations vary widely between individuals and include weakness and fatigue, dysphagia, cerebellar ataxia, sensorineural hearing loss, endocrinopathies, short stature, renal tubular acidosis, and cardiac conduction deficits. Tissues requiring high mitochondrial metabolic activity are most commonly affected including skeletal muscle, cardiac muscle, central nervous system and Retinal Pigment Epithelium (RPE). First described by Kearns and Sayre this disease is a primary mitochondrial disorder demonstrating progressive systemic and ocular manifestations. Kearns Sayre Syndrome (KSS), a rare genetic disease, links the triad of Chronic Progressive External Ophthalmoplegia (CPEO), pigmentary retinopathy, and cardiac conduction deficits. Kearns Sayre Syndrome articles Chronic Progressive External Ophthalmoplegia articles central nervous system articles Retina articles Article Details Introduction
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