The symptoms of Bernard-Soulier syndrome, which are typically apparent at birth and continue throughout life, may include the tendency to bleed excessively from cuts and other injuries, nosebleeds (epistaxis), and/or an unusually heavy menstrual flow in women. Some babies and children with BSS have no symptoms and the disorder does not present until adult life. People with this disease also bruise easily and the bruises tend to linger. Bleeding from very small blood vessels under the skin (subcutaneous) may cause small or widespread areas of small red or purple colored spots (purpura or petechiae).
BSS is a genetic disorder that affects the ability of the platelets in the circulating blood to bind with a damaged blood vessel and hence to clot blood. These platelets are missing an essential protein called the glycoprotein Ib-IX-V complex (GPIb). The Gp1b complex is composed of 4 proteins subunits that bind closely together (GP1b-alpha, GP1b-beta, GP9 and GP5). BSS is caused by mutations in one of the Gp1b complex genes- so far mutations have been found in BP1b-alpha, Gp1b-beta and GP9 but no mutations have been found in GP5). Normally the GP1b complex sticks out of the platelet’s surface and binds with another protein found in the circulating blood called von Willebrand factor. If one of these proteins is missing or abnormal, they cannot bind correctly to begin the clotting process and excessive bleeding results.
The abnormal genes in BSS have been mapped to chromosomes 17p13.2 (GP1b-alpha), 22q11.2 (GP1b-beta) and 3q21.3 (GP9). Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Each chromosome has a short arm designated as “p” and a long arm designated “q”. Chromosomes are further sub-divided into many bands that are numbered. For example, “chromosome 17p12″ refers to band 12 on the short arm of chromosome 17. The numbered bands specify the location of the thousands of genes that are present on each chromosome.
Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.
Bernard-Soulier syndrome is usually inherited as an autosomal recessive genetic trait. Recessive genetic disorders occur when an individual inherits an abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and, therefore, have an affected child is 25% with each pregnancy. The risk of having a child who is a carrier like the parents is 50% with each pregnancy. The chance that a child receives normal genes from both parents and is genetically normal for that particular trait is 25%. The risk is the same for males and females.
Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.
Bernard-Soulier syndrome is a rare bleeding disorder that affects males and females in equal numbers. Recent estimates suggest that Bernard Soulier syndrome affects 1 in a million people. More than 200 cases have been reported worldwide.
The diagnosis of Bernard-Soulier syndrome is made by a combination of blood testing to reveal whether platelets are at abnormally low levels (thrombocytopenia), microscopic examination to determine the presence of abnormally large platelets and irregularly shaped platelets, and biochemical tests to determine the capacity of the platelets to initiate clotting. Molecular genetic testing is available.
Platelet transfusion is used to treat Bernard-Soulier syndrome when surgery is necessary or when there is a risk for life-threatening hemorrhage. Some patients with Bernard-Soulier syndrome become resistant (refractory) to platelet transfusions because they develop antibodies against the GPIb protein- to reduce this risk it is now recommended that specially selected platelet transfusions (from HLA-matched single donors) should be used. Where HLA-matched platelets are not available, leucocyte-depleted platelets can be used (these are platelet transfusions from which contaminating white blood cells-leucocytes- have been removed). People with this disorder should not take aspirin or other related drugs because these medications affect the blood’s ability to clot (platelet aggregation). It is suggested that acetaminophen, which is present in medications such as Tylenol, is used for the relief of mild pain. Antifibrinolytic agents (drugs which delay the breakdown of blood clots) are often useful to help reduce bleeding after minor surgery (eg dental surgery) or for prolonged nosebleeds. The most commonly used antifibrinolytic drug is tranexamic acid (also known as epsilon aminocaproic acid).
Genetic counseling may be of benefit for people with Bernard-Soulier syndrome and their families. Other treatment is symptomatic and supportive.
Desmopressin acetate (DDAVP) has been shown to shorten bleeding time in some, but not all, patients with BSS. It may be useful for minor bleeding episodes.
More recently, recombinant activated factor VII and hematopoietic stem cell transplantation have been used in patients with congenital platelet disorders including BSS.
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