Genetic Disorders of Platelets

on 8.12.09 with 0 comments



Giant Platelets on a blood smear (40x).Image via Wikipedia


-remember that they are non nucleated vesicles that arise from megakaryocytes.

-mutation in many genes can interfere with the function of the platelets

-there have been more than 50 platelet plasma membrane proteins that have been recognized. And there are this many genes in which mutations can interrupt function. These 50 have been assigned into 5 gene families.

-Integrin family

-leucine rich glycoprotein’s

-immunoglobulin super family (three members)

-selectins

-seven transmembrane receptors

-huge multiplicity of genes and function can lead to many mutations. Given that platelets are so central in hemostasis there is a lot of potential for bleeding disorders that revolve around the mechanisms in disabling platelet function.

-platelet dysfunction can be described in several ways

-insufficiency, the number produced isn’t enough

-Bernard-Souliar Syndrome: Thrombocytopenia, in which thrombocytes are low in number.

-the granularity of the platelet is destroy or diminished or there are other specific genes that are not function because of the mutation, the platelet number is for the most part normal.

-Glanzmann Thrombasthenia- platelet fail to aggregate in their customary manner. Clot will stay loose and fail to harden. This is a rare disorder, and autosomal recessive.

-Platelet storage granule defects

-Hermanzkie-Pudlak Syndrome: This syndrome shows that you can have other system elements in the phenotype not just bleeding. There is severe albinism in addition to problem with bleeding. There is an accumulation in reticulo-endothelial cells in bone marrow and other tissues of a serous like material.

-Chediak-Higashi Syndrome- multi-system effects. There is partial albinism, you will see large granules cytologically in the platelets. You will also see large granules in leukocytes. This is therefore an immune dysfunction and a bleeding dysfunction. There are serous like deposits responsible for this.

-abnormality in platelet size and number

-T.A.R. Syndrome (Thromboyctopenia-Absence of Radius) involves anatomic formation and thrombocytopenia. If newborn baby present with an absence of the radius bone or thumb in one arm, you will want to do a platelet count. You will find that there may also be thrombocytopenia. X-linked inherited defect, seen mostly in baby boys. The thrombocytopenia that you see is hypomegakaryotciticĂ  the karyocytes look big, but the platelets (or thrombocytes) are not being derived from them in sufficient numbers.

-Whiskott-Aldrich Syndrome: a signal transduction defect, the cytoplasmic membrane receptor or an intracellular cascade protein is defective. This will lead to an insufficiency in platelet size. They are unusually small. There is a sever deficiency in number of platelets as well. There is a severe immune defect, and eczema (skin disorder).

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Category: Bone marrow , Cell membrane , Dominance , Glanzmann Thrombasthenia , Health , Medical Subject Notes , Platelet , Signal transduction , Thrombocytopenia

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