Mitochondrial myopathy-lactic acidosis-deafness syndrome

Mitochondrial myopathy-lactic acidosis-deafness syndrome (also referred to as mitochondrial myopathy with lactic acidosis and deafness) is an extremely rare mitochondrial disorder characterized by the triad of skeletal muscle dysfunction (myopathy), elevated lactic acid levels in the blood (lactic acidosis), and sensorineural hearing loss (deafness). The condition results from defects in mitochondrial function, impairing the ability of cells to produce energy efficiently through oxidative phosphorylation. This primarily affects tissues with high energy demands, including skeletal muscle, the inner ear, and the nervous system. Patients typically present with progressive muscle weakness and exercise intolerance due to the underlying myopathy. Lactic acidosis occurs because impaired mitochondrial energy production forces cells to rely on anaerobic metabolism, leading to accumulation of lactic acid. Sensorineural deafness develops due to the vulnerability of cochlear hair cells and auditory neurons to mitochondrial energy deficiency. Additional features may include neurological involvement and fatigue. Muscle biopsy often reveals characteristic findings such as ragged red fibers, indicative of abnormal mitochondrial proliferation. There is currently no cure for this syndrome. Treatment is primarily supportive and symptomatic, focusing on management of lactic acidosis, hearing aids or cochlear implants for hearing loss, and physical therapy for muscle weakness. Some clinicians may trial mitochondrial cofactors and supplements such as coenzyme Q10, L-carnitine, and B vitamins, although evidence for their efficacy in this specific condition remains limited. Regular monitoring by a multidisciplinary team including neurologists, audiologists, and metabolic specialists is recommended.

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