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X-linked thrombocytopenia, also referred to as XLT or Thrombocytopenia 1, is an inherited clotting disorder that primarily affects males. It is a ''WAS''-related disorder, meaning it is caused by a mutation in the Wiskott-Aldrich Syndrome (''WAS'') gene, which is located on the short arm of the X chromosome. ''WAS''-related disorders include Wiskott-Aldrich syndrome, XLT, and X-linked congenital neutropenia (XLN). Of the ''WAS''-related disorders, X-linked thrombocytopenia is considered to be the milder phenotype. Between 1 and 10 per million males worldwide are affected with this disorder. Females may be affected with this disorder but this is very rare since females have two X chromosomes and are therefore typically carriers of the mutation. ==Mechanism== X-linked thrombocytopenia primarily affects the circulatory system, specifically the platelets in the blood. Platelets are cell fragments in the blood that aid in clotting. Platelets are produced in the bone marrow. Normal platelet counts range from 150,000 to 450,000 platelets per µL of blood. Individuals with XLT usually have drastically reduced platelet counts, typically less than 70,000 platelets per µL of blood. Not only are there fewer platelets circulating, but individuals with XLT also have smaller platelets. Fewer and smaller platelets causes the efficacy of the clotting mechanism in the body to be seriously compromised, which can lead to bruising and bleeding. X-linked thrombocytopenia is caused by a mutation of the ''WAS'' gene. This mutation causes the decreased, absent, or altered Wiskoff-Aldrich syndrome protein (WASp). Normal WASp is involved in relaying signals from the cell membrane to the actin cytoskeleton. If WASp is decreased, absent, or altered, then the hematopoietic cells it is found in will show signaling and cytoskeleton abnormalities. This form of thrombocytopenia is inherited on X chromosome, thus individuals with this disorder are typically males. In regards to the sex chromosomes, males have one X chromosome and one Y chromosome while females have two X chromosomes. Because males only have one X chromosome, if they receive an X chromosome with a ''WAS'' gene mutation from their mother, then they will show phenotype of the condition. Females can be carriers for this disorder, which means that they have one normal X chromosome and one X chromosome with the ''WAS'' gene mutation. Females that are carriers do not show any signs or symptoms of X-linked thrombocytopenia. Males with X-linked thrombocytopenia are also susceptible to severe infections, bleeding, autoimmune diseases and malignancies. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「X linked thrombocytopenia」の詳細全文を読む スポンサード リンク
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