Bernard-Soulier syndrome is an autosomal recessive bleeding disorder caused by a defect in or deficiency of the platelet membrane von Willebrand factor (VWF; 613160) receptor complex, glycoprotein Ib (GP Ib). GP Ib is composed of 4 subunits encoded by 4 separate genes: GP1BA, GP1BB, GP9, and GP5 (173511). Genetic Heterogeneity of Platelet-Type Bleeding Disorders Inherited platelet disorders are a heterogeneous group of bleeding disorders affecting platelet number, function, or both. Functional defects can involve platelet receptors, signaling pathways, cytoskeletal proteins, granule contents, activation, or aggregation (review by Cox et al., 2011 and Nurden and Nurden, 2011). Platelet-type bleeding disorders include Bernard-Soulier syndrome (BDPLT1); Glanzmann thrombasthenia (BDPLT2; 273800), caused by mutation in the ITGA2B (607759) or ITGB3 (173470) gene; pseudo-von Willebrand disease (BDPLT3; 177820), caused by mutation in the GP1BA gene (606672); gray platelet syndrome (BDPLT4; 139090), caused by mutation in the NBEAL2 gene (614169); Quebec platelet disorder (BDPLT5; 601709), caused by tandem duplication of the PLAU gene (191840); May-Hegglin anomaly (BDPLT6; 155100), caused by mutation in the MYH9 gene (160775); Scott syndrome (BDPLT7; 262890), caused by mutation in the TMEM16F gene (608663); BDPLT8 (609821), caused by mutation in the P2RY12 gene (600515); BDPLT9 (614200), associated with deficiency of the glycoprotein Ia/IIa receptor (see ITGA2; 192974); glycoprotein IV deficiency (BDPLT10; 608404), caused by mutation in the CD36 gene (173510); BDPLT11 (614201), caused by mutation in the GP6 gene (605546); BDPLT12 (605735), associated with a deficiency of platelet COX1 (176805); susceptibility to BDPLT13 (614009), caused by mutation in the TBXA2R gene (188070); BDPLT14 (614158), associated with deficiency of thromboxane synthetase (TBXAS1; 274180); BDPLT15 (615193), caused by mutation in the ACTN1 gene (102575); BDPLT16 (187800), caused by mutation in the ITGA2B (607759) or ITGB3 (173470) gene; BDPLT17 (187900), caused by mutation in the GFI1B gene (604383); BDPLT18 (615888), caused by mutation in the RASGRP2 gene (605577); BDPLT19 (616176), caused by mutation in the PRKACG gene (176893); BDPLT20 (616913), caused by mutation in the SLFN14 gene (614958); BDPLT21 (617443), caused by mutation in the FLI1 gene (193067); BDPLT22 (618462), caused by mutation in the EPHB2 gene (600997); BDPLT23 (619267), caused by mutation in the ITGB3 gene (173470); BDPLT24 (619271), caused by mutation in the ITGB3 gene (173470); and BDPLT25 (620486), caused by mutation in the TPM4 gene (600317). See reviews by Rao (2003), Cox et al. (2011), and Nurden and Nurden (2011). For a discussion of the genetic heterogeneity of hereditary thrombocytopenia, see THC1 (313900).

DFNA1 is an autosomal dominant form of progressive hearing loss with onset in the first decade. Some patients have mild thrombocytopenia and enlarged platelets, although most of these individuals do not have significant bleeding tendencies (summary by Neuhaus et al., 2017).

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).

An extremely rare form of carbohydrate deficient glycoprotein syndrome characterized clinically in the single reported case by repeated hemorrhagic incidents, including severe pulmonary hemorrhage.

A rare isolated hereditary giant platelet disorder characterized by severe thrombocytopenia and thrombopathy due to defects in proplatelet formation and platelet activation in homozygous patients. Clinical manifestation are recurrent bleeding episodes including epistaxis, spontaneous hematomas, and menorrhagia.

MYH9-related disease (MYH9-RD) is characterized in all affected individuals by hematologic features present from birth consisting of platelet macrocytosis (i.e., >40% of platelets larger than 3.9 µm in diameter), thrombocytopenia (platelet count <150 x 109/L), and aggregates of the MYH9 protein in the cytoplasm of neutrophil granulocytes. Most affected individuals develop one or more additional extrahematologic manifestations of the disease over their lifetime, including sensorineural hearing loss, renal disease (manifesting initially as glomerular nephropathy), presenile cataracts, and/or elevation of liver enzymes.

Platelet-type bleeding disorder-16 (BDPLT16) 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). Genetic Heterogeneity of Glanzmann Thrombasthenia-like with Macrothromocytopenia See BDPLT24 (619271), caused by mutation in the ITGB3 gene (173470) on chromosome 17q21.32. Together the ITGB2B and ITBG3 genes form an integrin, known as platelet glycoprotein GPIIb/III, that is expressed on platelets.

Autosomal dominant isolated macrothrombocytopenia-1 (MACTHC1) is characterized by the finding of low platelet numbers and abnormally large platelets with irregular shapes. Affected individuals do not have increased bleeding episodes and platelet function is normal; macrothrombocytopenia is usually an incidental laboratory finding (Kunishima et al., 2009). Genetic Heterogeneity of Isolated Macrothrombocytopenia See also MACTHC2 (619840), caused by mutation in the TUBA8 gene (605742) on chromosome 22q11.

Autosomal dominant isolated macrothrombocytopenia-2 (MACTHC2) is characterized by the finding of low platelet numbers and abnormally large platelets with irregular shapes. Affected individuals do not have increased bleeding episodes; macrothrombocytopenia is usually an incidental laboratory finding (Kimmerlin et al., 2022) For a discussion of genetic heterogeneity of MACTHC, see MACTHC1 (613112).