April 6, 2009 --
Severe combined immune-deficiency (SCID) is a genetic disorder that affects about one of every 100,000 babies. The disease is sometimes referred to as the "Bubble Boy" disease because of David Vetter, a boy with SCID who lived in a plastic bubble for 12 years. It is a disorder in which both parts of the adaptive immune system -- the B-cells and the T-cells -- are crippled due to a genetic defect. The immune system is a network of organs, tissues, cells and protein substances that combine to fight off bacteria, fungi, viruses and parasites. When foreign antigens are found in the immune system, it acts as a destroyer. If the body has a healthy and functioning immune system, it can fight off dangerous antigens. Those with severe combined immune-deficiency are extremely vulnerable to infectious diseases because of their lack of an immune system. They must stay away from germ-rich environments such as day-care centers or crowded theatres where they may be susceptible to infection. Normally, symptoms of the disease appear in the first few months of life. Babies with SCID generally get one infection after another because their body can not fight off disease. Most of the time, these babies will not respond to antibiotics and suffer from ear infections, chronic cough, sinus infections and chronic diarrhea. TREATMENT:
Currently, the most effect treatment for SCID is a bone marrow transplant. Stem cells are taken from a healthy donor's bone marrow and injected into the patient. If the treatment goes well, the stem cells will stimulate the production of necessary immune and blood cells. Most transplants performed within the first few months of life are successful, however it is important that the donor tissue matches the patient. Siblings, or matched donors, make the best donors because they have the most similar genetic make-up. A half-matched donor, or a parent, can also provide a good match. A clinical trial that involves giving chemotherapy before the bone marrow transplant is currently underway at the University of Miami School of Medicine. "If you give chemotherapy you make it easier for the new cells to grow and we think that it actually makes the immune system come in better later down the road," Gary Kleiner, M.D., Ph.D., a pediatric immunologist at the University of Miami School of Medicine, told Ivanhoe.
FIXING COMPLICATIONS: While bone marrow transplants are effective for developing T-cells in patients with SCID, they sometimes cause complications. Veno-occlusive disease (VOD) is a condition in which some of the small vessels in the liver are blocked. The complication can arise due to the high-dose chemotherapy given before a bone marrow transplant. Symptoms include increased liver size, weight gain and clotting problems. A phase III clinical trial is currently investigating the use of the drug defibrotide as a potential treatment for VOD. Dibribrotide is believed to work by prevnting clotting in the blood vessels and by helping dissolve clots. Without treatment, VOD is often a fatal condition.
FOR MORE INFORMATION, PLEASE CONTACT:
Omar Montejo, Director of Media Relations
University of Miami School of Medicine