Mitochondrial diseases are a group of disorders caused by dysfunction in the mitochondria, which are 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. The severity and type of symptoms can vary widely among individuals, as mitochondrial diseases can be inherited or occur spontaneously. Diagnosis often involves genetic testing and may require specialized treatments to manage symptoms, but there is currently no cure for these conditions.