ITGB3 and Glanzmann thrombasthenia: Other receptors include the receptor for fibrinogen, integrin GPIIb-IIIa, which is encoded by the genes ITGA2B and ITGB3. Affected mutations in ITGA2B and ITGB3 have been identified to cause Glanzmann thrombasthenia (GT) (71), but patients have a normal platelet count.