This term refers to a group of disorders having somewhat similar clinical features secondary to mutations in the DNA of mitochondria which leads to deficits in cellular energy pathways. The majority of our DNA is contained within the nucleus of our cells but a small amount is found in small organelles known as mitochondria that reside outside the nucleus. The proteins in mitochondria are vitally important to the proper utilization of oxygen and derivation of energy for metabolism. Hence, mutations in their DNA often have devastating consequences.
Onset of clinical symptoms may occur at any time but most patients become symptomatic sometime in the first two decades of life. In infants and young children the primary symptoms are failure to thrive, developmental delays, and learning disabilities. Older individuals often present with sudden, severe headaches accompanied by vomiting and seizures. These may resemble migraines. Weakness, lethargy, and apathy are common. Many of the symptoms result from stroke-like episodes. The disease is progressive and over time individuals often lose initiative, become more apathetic and sometimes become demented.
Hearing and vision are often impaired. Heart disease, diabetes, and thyroid disease are common. MRIs of the brain can demonstrate loss of brain tissue and accumulation of calcium. Numbness and tingling may be experienced in the limbs and digits.
The mutations causing MELAS occur in the DNA of mitochondria, the energy factories of our cells. Since only females transmit mitochondria to their offspring, the inheritance pattern is usually one of transmission through the maternal side. However, there can be a great deal of variation in the number of affected mitochondria transmitted so that it is not possible to predict accurately what the risks are to offspring.
The diagnosis requires a collaborative effort among pediatricians, neurologists, and radiologists. Patients with vision difficulties should have an evaluation by an ophthalmologist as wellThere is no effective treatment to prevent this disease nor can damaged brain tissue be replaced or repaired. Morbidity and early mortality are high.