What is Bernard-Soulier syndrome?
Bernard-Soulier syndrome (Bernard-Soulier syndromeBSS, hemorrhagic platelet dystrophy) is a rare hereditary disease, affecting blood clotting (coagulation), which is characterized by abnormally large platelets, a low platelet count (thrombocytopenia) and prolonged bleeding time (difficulty in blood clotting). Affected individuals are at increased risk of excessive bleeding and easy bruising. Most cases of Bernard-Soulier syndrome are inherited in an autosomal recessive genetic pattern.
What are the signs and symptoms of Bernard-Soulier syndrome?
Symptoms of Bernard-Soulier syndrome, which are usually present at birth and last throughout life, may include a tendency to bleed excessively cuts and other injuries, nosebleeds (epistaxis) and/or unusually heavy menstrual flow in women.
Some babies and children with Bernard-Soulier syndrome have no symptoms, and the disorder does not manifest itself until adulthood. People affected by this disease also bruise easily, which they last longer than usual. Bleeding from very small blood vessels under the skin can cause small or widespread areas of red or purple small spots (purpura or petechiae).
What are the causes of Bernard-Soulier syndrome?
Bernard-Soulier syndrome is a genetic disorder that affects the ability of platelets (platelets) in circulating blood to bind to a damaged blood vessel and therefore clot the blood. These platelets are missing an essential protein called glycoprotein Ib-IX-V complex (GP1b). The GP1b complex is composed of 4 protein subunits that bind tightly to each other (GP1b-alpha, GP1b-beta, GP9 and GP5). Bernard-Soulier syndrome is caused by mutations in one of the genes of the GP1b complex – 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 comes off the platelet surface and binds to another protein found in circulating blood called von Willebrand factor. If one of these proteins is missing or abnormal, they cannot bind properly to start the clotting process and excessive bleeding occurs.
Bernard-Soulier syndrome is usually inherited by autosomal recessive genetic pattern. Autosomal recessive genetic disorders occur when a person inherits an abnormal gene for a trait from each parent. If the person receives one normal gene and one abnormal gene for the disease, the person will be a carrier of the disease, but will usually show no symptoms.
The risk for two carrier parents to pass on the abnormal gene and therefore have an affected child is 25% in each pregnancy. The risk of giving birth to a child who is a carrier of the disease, like its parents, is 50% with each pregnancy. The chance that the child will receive normal genes from both parents is 25%. The risk is the same for men and women.
Bernard-Soulier syndrome is a rare blood clotting disorder that affects in the same frequency men and women. Recent estimates suggest that Bernard-Soulier syndrome affects 1 in a million people. More than 200 cases of the disease have been registered worldwide.
References:
1. Rao AK. Bernard-Soulier Syndrome. In: NORD Guide to Rare Disorders. Lippincott Williams & Wilkins
2. Beers MH, Berkow R., eds. The Merck Manual, 17th ed. Whitehouse Station, NJ: Merck Research Laboratories
3. Hoffman R, Benz Jr EJ, Shattil SJ et al. Eds. Hematology: Basic Principles and Practice. 2nd ed.
