MedGen

Thrombocythemia, or thrombocytosis, is a myeloproliferative disorder characterized by excessive platelet production resulting in increased numbers of circulating platelets. Thrombocythemia can be associated with thrombotic or hemorrhagic episodes and occasional leukemic transformation (summary by Wiestner et al., 1998). Genetic Heterogeneity of Thrombocythemia THCYT2 (601977) is caused by germline or somatic mutation in the THPO receptor gene (MPL; 159530) on chromosome 1p34, and THCYT3 (614521) is caused by germline or somatic mutation in the JAK2 gene (147796) on chromosome 9p. Somatic mutations in the TET2 (612839), ASXL1 (612990), SH2B3 (605093), and SF3B1 (605590) genes have also been found in cases of essential thrombocythemia. Somatic mutation in the CALR gene (109091) occurs in approximately 70% of essential thrombocythemia patients who lack JAK2 and MPL mutations (Klampfl et al., 2013; Nangalia et al., 2013). [from OMIM]

Hermansky-Pudlak syndrome (HPS) is characterized by oculocutaneous albinism, a bleeding diathesis, and, in some individuals, pulmonary fibrosis, granulomatous colitis, or immunodeficiency. Ocular findings include reduced iris pigment with iris transillumination, reduced retinal pigment, foveal hypoplasia with significant reduction in visual acuity (usually in the range of 20/50 to 20/400), nystagmus, and increased crossing of the optic nerve fibers. Hair color ranges from white to brown; skin color ranges from white to olive and is usually a shade lighter than that of other family members. The bleeding diathesis can result in variable bruising, epistaxis, gingival bleeding, postpartum hemorrhage, colonic bleeding, and prolonged bleeding with menses or after tooth extraction, circumcision, and other surgeries. Pulmonary fibrosis, a restrictive lung disease, typically causes symptoms in the early thirties and can progress to death within a decade. Granulomatous colitis is severe in about 15% of affected individuals. Neutropenia and/or immune defects occur primarily in individuals with pathogenic variants in AP3B1 and AP3D1. [from GeneReviews]

RUNX1 familial platelet disorder with associated myeloid malignancies (RUNX1-FPDMM) is characterized by prolonged bleeding and/or easy bruising and an increased risk of developing a hematologic malignancy. RUNX1-FPDMM is characterized by thrombocytopenia with normal platelet size; bleeding is often greater than expected due to qualitative platelet dysfunction. Myeloid malignancies are the most common, including acute myelogenous leukemia (and myelodysplastic syndrome. T- and B-cell acute lymphoblastic leukemias and lymphomas have also been reported, as well as skin manifestations (e.g., eczema, psoriasis). [from GeneReviews]

Wolfram syndrome-2 (WFS2) is an autosomal recessive neurodegenerative disorder characterized by diabetes mellitus, high frequency sensorineural hearing loss, optic atrophy or neuropathy, and defective platelet aggregation resulting in peptic ulcer bleeding (summary by Mozzillo et al., 2014). For a discussion of genetic heterogeneity of Wolfram syndrome, see WFS1 (222300). [from OMIM]

The gray platelet syndrome (GPS) is a rare inherited disorder characterized by mild to moderate bleeding tendency, moderate thrombocytopenia, and a marked decrease or absence of platelet alpha-granules and of the proteins contained in alpha-granules. The platelets are enlarged, but not giant, and have a gray appearance on light microscopy of Wright-stained peripheral blood smears due to decreased granules. Many patients with gray platelet syndrome develop a stable myelofibrosis (summary by Nurden and Nurden, 2007). Cases suggesting autosomal dominant and autosomal recessive inheritance have been described, indicating that GPS is probably a genetically heterogeneous disorder with more than one molecular cause. [from OMIM]

Glanzmann thrombasthenia is a bleeding disorder that is characterized by prolonged or spontaneous bleeding starting from birth. People with Glanzmann thrombasthenia tend to bruise easily, have frequent nosebleeds (epistaxis), and may bleed from the gums. They may also develop red or purple spots on the skin caused by bleeding underneath the skin (petechiae) or swelling caused by bleeding within tissues (hematoma). Glanzmann thrombasthenia can also cause prolonged bleeding following injury, trauma, or surgery (including dental work). Women with this condition can have prolonged and sometimes abnormally heavy menstrual bleeding. Affected women also have an increased risk of excessive blood loss during pregnancy and childbirth.

About a quarter of individuals with Glanzmann thrombasthenia have bleeding in the gastrointestinal tract, which often occurs later in life. Rarely, affected individuals have bleeding inside the skull (intracranial hemorrhage) or joints (hemarthrosis).

The severity and frequency of the bleeding episodes in Glanzmann thrombasthenia can vary greatly among affected individuals, even in the same family. Spontaneous bleeding tends to become less frequent with age. [from MedlinePlus Genetics]

Platelet-type bleeding disorder-17 is an autosomal dominant disorder characterized by increased bleeding tendency due to abnormal platelet function. It is a type of 'gray platelet syndrome' because the platelets appear abnormal on light microscopy. Electron microscopy shows decreased or absent alpha-granules within platelets, and bone marrow biopsy shows increased numbers of abnormal megakaryocytes, suggesting a defect in megakaryopoiesis and platelet production. The bleeding severity is variable (summary by Monteferrario et al., 2014). [from OMIM]

Platelet-type bleeding disorder-11 is an autosomal recessive mild to moderate bleeding disorder caused by defective platelet activation and aggregation in response to collagen (summary by Dumont et al., 2009). [from OMIM]

Hermansky-Pudlak syndrome (HPS) is characterized by oculocutaneous albinism, a bleeding diathesis, and, in some individuals, pulmonary fibrosis, granulomatous colitis, or immunodeficiency. Ocular findings include reduced iris pigment with iris transillumination, reduced retinal pigment, foveal hypoplasia with significant reduction in visual acuity (usually in the range of 20/50 to 20/400), nystagmus, and increased crossing of the optic nerve fibers. Hair color ranges from white to brown; skin color ranges from white to olive and is usually a shade lighter than that of other family members. The bleeding diathesis can result in variable bruising, epistaxis, gingival bleeding, postpartum hemorrhage, colonic bleeding, and prolonged bleeding with menses or after tooth extraction, circumcision, and other surgeries. Pulmonary fibrosis, a restrictive lung disease, typically causes symptoms in the early thirties and can progress to death within a decade. Granulomatous colitis is severe in about 15% of affected individuals. Neutropenia and/or immune defects occur primarily in individuals with pathogenic variants in AP3B1 and AP3D1. [from GeneReviews]

Platelet-type bleeding disorder-24 (BDPLT24) is an autosomal dominant form of congenital macrothrombocytopenia associated with platelet anisocytosis. It is a disorder of platelet production. Affected individuals may have no or only mildly increased bleeding tendency. In vitro studies show mild platelet functional abnormalities (summary by Kunishima et al., 2011 and Nurden et al., 2011). For a discussion of genetic heterogeneity of Glanzmann thrombasthenia-like with macrothrombocytopenia, see 187800. [from OMIM]

Glanzmann thrombasthenia-2 (GT2) is an autosomal recessive bleeding disorder characterized by failure of platelet aggregation and by absent or diminished clot retraction. The abnormalities are related to quantitative or qualitative abnormalities of the GPIIb (607759)/IIIa platelet surface fibrinogen receptor complex resulting from mutations in the GPIIIa gene (Rosenberg et al., 1997). For a general phenotypic description and a discussion of genetic heterogeneity of Glanzmann thrombasthenia, see 273800. [from OMIM]

Immunodeficiency-81 (IMD81) is an autosomal recessive complex immunologic disorder with onset of symptoms in infancy. The phenotype is highly variable and may include both immunodeficiency with recurrent infections, including bacterial and fungal infections, as well as autoimmune features, including autoimmune hemolytic anemia, pancytopenia, thrombocytopenia, and inflammatory bowel disease. Immunologic workup shows immune dysregulation with abnormalities affecting multiple immune cell lineages, including T cells, B cells, NK cells, and neutrophils, which may be decreased or increased and demonstrate functional deficits. There is a wide range of hematologic abnormalities. Affected individuals may be susceptible to severe EBV infection. The disorder is caused by a defect in intracellular immune signaling pathways (summary by Lev et al., 2021; Edwards et al., 2023). [from OMIM]

Platelet-type bleeding disorder-25 (BDPLT25) is an autosomal dominant condition characterized by increased susceptibility to bleeding episodes due to decreased or dysfunctional platelets. Some individuals have decreased numbers of enlarged platelets or macrothrombocytopenia, whereas others have normal numbers of enlarged platelets. Platelet morphologic and functional defects are variable (Pleines et al., 2017; Stapley et al., 2022; Marin-Quilez et al., 2022). For a discussion of genetic heterogeneity of BDPLT, see 231200. [from OMIM]

Platelet-type bleeding disorder-22 (BDPLT22) is an autosomal recessive bleeding disorder resulting from impaired platelet aggregation due to intracellular signaling defects. Patients present in the first decade with spontaneous subcutaneous bleeding and excessive bleeding after minor injuries. Platelet counts are usually normal, although platelets show abnormal morphology (summary by Berrou et al., 2018). [from OMIM]

Thrombocytopenia-7 (THC7) is an autosomal dominant disorder characterized by reduced peripheral platelet count. The expression and severity of the disorder is highly variable: some patients have no bleeding symptoms, whereas other have recurrent petechiae, epistaxis, or more severe bleeding episodes. A common finding is decreased alpha-granules in the platelets. There are variable findings on light and electron microscopic analysis: some patients have normal platelet morphology, whereas others show abnormal platelet morphology with cytoskeletal defects. Flow cytometric studies may show reduced expression of platelet membrane glycoproteins and activation markers (summary by Lentaigne et al., 2019 and Leinoe et al., 2021). For a general phenotypic description and a discussion of genetic heterogeneity of thrombocytopenia, see 313900. [from OMIM]

Abnormal response to collagen or collagen-mimetics as manifested by reduced or lacking aggregation of platelets upon addition collagen or collagen-mimetics. [from HPO]