Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS)
affects many parts of the body, particularly the brain and nervous system (encephalo-) and muscles (myopathy). Symptoms typically begin in childhood and may include muscle weakness and pain, recurrent headaches, loss of appetite, vomiting, and seizures. Most affected individuals experience stroke-like episodes beginning before age 40. People with MELAS can also have a buildup of lactic acid in their bodies that can lead to vomiting, abdominal pain, fatigue, muscle weakness, and difficulty breathing. The genes associated with MELAS are located in mitochondrial DNA and therefore follow a maternal inheritance pattern (also called mitochondrial inheritance). MELAS can be inherited from the mother only, because only females pass mitochondrial DNA to their children. In some cases, MELAS results from a new mutation that was not inherited from a person's mother. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.