DOCUMENT

WINTER 2025 InTouch | 17 Visual impairment (retinitis pigmentosa, optic neuropathy and cataracts) If there is a history of developmental delays, learning disabilities or attention deficit disorder then this is typically discovered before the first stroke has been experienced. MELAS SYNDROME on one side of the body, altered consciousness, vision abnormalities, seizures, and severe headaches resembling migraines. Repeated stroke-like episodes can progressively damage the brain, leading to vision loss, problems with movement, and a loss of intellectual function (e.g. dementia). If there is a history of developmental delays, learning disabilities or attention deficit disorder then this is typically discovered before the first stroke has been experienced. Genetics of MELAS MELAS is caused by a defect in one of several mitochondrial genes. Mitochondrial (mt) genes are found in the DNA of cellular structures called mitochondria, which convert the energy from food into a form that cells can use, not in the nucleus of a cell like typical DNA. The genes that are not working correctly can be in any of these mitochondrial genes called MTND1, MT-ND5, MT-TH, MT- TL1, and MT-TV. Both normal and mutated mtDNA can exist in the same cell, which is a situation known as heteroplasmy. Symptoms may not appear until the mutation affects a significant proportion of mtDNA. The uneven distribution of normal and mutant mtDNA in different tissues can affect different organs in members of the same family. This can result in a variety of symptoms in affected family members. Mutations in the mtDNA gene MT- TL1 cause more than 80 percent of all cases of MELAS. These mutations impair the ability of mitochondria to make proteins, use oxygen, and produce energy. Researchers have not determined how changes in mtDNA lead to the specific signs and symptoms of MELAS. They continue to investigate the effects of mitochondrial gene mutations in different tissues, particularly in the brain. Children can only inherit this disorder from their mother. This is because egg cells contribute the mitochondria to the developing embryo, and sperm do not. The condition can appear in every generation of a family and can affect both males and females, but fathers do not pass traits associated with changes in mtDNA to their children. In most cases, people with MELAS inherit an altered mitochondrial gene from their mother. Less commonly, the disorder results from a new mutation Continued over ... Features of Mitochondrial Disease • Cardiomyopathy • Conduction defects • Malabsorption • Diarrhoea • Infertility • Premature menopause • Anaemia • Immunological defects • Lactacidaemia Kidney dysfunction Diabetes Hearing deficit • Muscle weakness • Cramps • Tiredness in exercise Brain pathology e.g.: • Epilepsy • Strokes • Cognitive decline • Migraine Sensory or motor neuropathies Liver disease