Approximately 3 to 4 percent of all babies are born with a genetic disease or birth defect, according to information provided by Net Wellness. Genetic diseases are those that are passed down from parent to child through damaged or defective genes, specific sequences of DNA (deoxyribose nucleic acid) found in specific locations on chromosomes and responsible for specific functions or characteristics.
Alpha Thalassemia Major
Thalassemia is a term used to describe a group of blood disorders that are inherited. In all forms of thalassemia the body does not produce enough red blood cells, which leads to a deficiency in hemoglobin, the protein found in red blood cells that carries oxygen throughout the body. This results in anemia, which may range from mild to severe depending on which and how many genes are affected.
Hemoglobin is made up of four protein chains, according to the National Heart Lung and Blood Institute, two denoted as alpha and two as beta. The alpha chains require four healthy genes to be present and the beta chains need two genes.
When more than two of the genes required for the alpha chain are affected, the result is moderate to severe anemia. The fatal form of this disease, known as alpha thalassemia major, can lead to hydrops fetalis, which involves abnormal fluid buildup in the body. This form of thalassemia usually results in death shortly after birth.
Severe Combined Immunodeficiency
Severe combined immunodeficiency, also known as "bubble boy" disease, is a condition where the body has little to no immune response. Those with this condition have a defect in their white blood cells, both T cells and B cells, which help the body fight off infections. This usually results in very serious and many times fatal infections within the first few months of life.
Approximately 50 percent of severe combined immunodeficiency cases are linked to the X chromosome, according to the information provided in "Genes and Disease," meaning that it is passed on from mothers to their sons. There is another form of SCID that is linked to a gene on chromosome 20 and involves a deficient amount of the enzyme adenosine deaminase, which leads to a buildup of toxic material in the immature immune cells resulting in death of the immune cells.
Although there are treatments available for SCID, the condition is usually not discovered until the patients are very sick with infections, resulting in death.
Zellweger Syndrome
Zellweger Syndrome is the most severe disease in the group of diseases known as leukodystrophies. This genetic condition is caused by defects in genes that are active in brain development and results in a deficiency in peroxisomes, which are cell structures that break down toxic material produced by the liver, kidneys and brain. Patients with Zellweger Syndrome have a buildup of copper and iron, which causes an enlarged liver, facial deformities, mental retardation and seizures. Those suffering from this fatal disease usually die within the first six months of life due to respiratory distress, intestinal bleeding or liver failure.
