Info

Thrombocy

Leukocyte

sensorineural

Disorder

topenia

inclusions Nephritis

deafness Cataracts

May Hegglin anomaly

+

+ —

— —

Sebastian syndrome

+

+ —

— —

Epstein syndrome

+

—+

+ —

Fechtner syndrome

+

+ +

+ +

Alport syndrome

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—+

+ +

Platelet Secretion Defects with Normal Granule Stores and Normal Thromboxane Synthesis (Table 10-12)

Several studies have identified patients with a mild bleeding diathesis whose platelets have normal granule stores and normal thromboxane A2 synthesis during stimulation. This category also includes patients with behavioral attention deficit disorder or minimal brain damage syndrome and easy bruising. Many affected patients have abnormalities in the aggregation and secretion responses to weak agonists (ADP, adrenaline) but not to relatively stronger agonists such as arachidonic acid or higher concentrations of collagen.

Defects in Ca2+ Mobilization

A number of key platelet processes are Ca2+ dependent (e.g., liberation of arachidonic acid and phosphorylation of myosin light chain). Patients with deficient Ca2+ mobilization have been reported.

Deficiency of Platelet Procoagulant Activity (Table 10-12)

Platelets contain several coagulation factors in their granules and provide negatively charged lipid surfaces on which a number of key coagulation enzymatic reactions proceed. Platelet factor 3 reflects the contribution of platelets to the interaction of factors Xa, Va, and Ca2+ in prothrombin activation. In Scott syndrome, platelets have a decreased number of factor Xa binding sites. Bleeding time, platelet aggregation, and secretion are normal. The patients have a shortened PT as a result of reduced pro-thrombin consumption.

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