Mitochondrial disease refers to a group of disorders caused by dysfunctional mitochondria, the energy-producing structures in cells. These diseases can affect various organs and systems, leading to symptoms such as muscle weakness, neurological issues, and problems with growth and development. Mitochondrial diseases can be inherited or occur spontaneously. Diagnosis often involves genetic testing and muscle biopsies. Treatment focuses on managing symptoms and may include dietary changes, supplements, and physical therapy. Research is ongoing to better understand these conditions and develop potential therapies, as there is currently no cure for mitochondrial disease.