Each person has a unique set of genes inherited from his parents, with each parent contributing half of their offspring's genes. Autosomal dominant genes can affect a child if only one parent passes it on. Children have a 50 percent chance of inheriting the gene. Diseases that are lethal at a young age are never autosomal dominant, because the person wouldn't live long enough to pass it on. Autosomal dominant diseases that are lethal later in life or that are mild enough not to cause early death can be passed on.
Huntington's Disease
Huntington's disease is the best known example of an autosomal dominant disease. Because symptoms don't generally develop until middle age, a person has time to have children and pass on the gene before she realizes she has the disease. Everyone who inherits the gene will develop the disease if they live long enough, the Mayo Clinic states. Huntington's disease develops slowly, beginning with cognitive changes such as memory problems, difficulty answering questions or making decisions, anger, depression or loss of interest in daily activities.
Physical changes include clumsiness and involuntary facial movements. Severe coordination and balance problems develop, along with jerky movements, difficulty swallowing, slurred speech and finally, dementia. Death usually occurs 10 to 30 years after symptoms first appear.
Marfan Syndrome
Marfan syndrome is an autosomal dominant disease that causes problems with connective tissue. It affects approximately one in 5,000 men, women and children, the National Heart Lung and Blood Institute states. Since connective tissue is found all over the body, many body organs, including the heart, can be affected. Typical Marfan syndrome symptoms include long arms, legs, fingers and toes, and a tall thin, build. Scoliosis, spinal curvature and a sunken or protruding breast bone may occur along with flat feet and overly crowded teeth. The aorta, the artery that carries blood from the heart, may be weak and stretched, a condition called aortic aneurysm. The aneurysm may burst, leading to sudden death. People with Marfan syndrome can live a normal lifespan if diagnosed and treated early.
Neurofibromatosis-1
Neurofibromatosis-1, an autosomal dominant disease, is characterized by nerve tissue tumors that develop in the skin and brain. Neurofibromas, which are usually not cancerous, generally begin to appear by age 2. Café au lait spots, spots the color of coffee with cream, and freckles appear on the skin. Tumors may grow in the eye and lead to blindness. Tissue along the nerves grows and puts pressure on the nerves causing pain and loss of function, the University of Maryland Medical Center states.
