Syndrome of the week

Glanzmann's thrombasthenia is an extremely rare disorder of the blood, in which the platelets lack glycoprotein IIb/IIIa. Hence, no fibrinogen bridging can occur, and bleeding time is significantly prolonged.

The GpIIb/IIIa is an adhesion receptor and is expressed in thrombocytes. This receptor is activated when the thrombocyte is stimulated by ADP, epinephrine, collagen and thrombin. The GpIIb/IIIa integrin is essential to the blood coagulation since it has the ability to bind fibrinogen, the von Willebrand factor, fibronectin and vitronectin. This enables the platelet to be activated by contact with the collagen-von Willebrand-complex that is exposed when the endothelial blood vessel lining is damaged and then aggregate with other thrombocytes via fibrinogen.

Patients suffering from Glanzmann's thrombasthenia thus have platelets less able to adhere to each other and to the underlying tissue of damaged blood vessels.
The understanding of its pathophysiology led to the development of GpIIb/IIIa inhibitors, a class of powerful antiplatelet agents.
Glanzmann's thrombasthenia can be inherited in an autosomal recessive manner or acquired as an autoimmune disorder.

Characteristically, there is increased mucosal bleeding:
epistaxis
menorrhagia
increased bleeding post-operatively.

The bleeding tendency is variable but may be severe.
Patients present with moderate bleeding and normal platelet morphology. Aggregation of platelets occurs in response to ristocetin, but not to other agonists such as ADP, thrombin, collagen or epinephrine.

It is named for Eduard Glanzmann.