Platelets from the proband (LD) do not support fibrinogen-dependent platelet aggregation.

Platelet-rich plasma (PRP) from patient LD was stirred in an aggregometer at 37°C before the addition of agonists (time point indicated by arrow). Platelets from LD showed no aggregation in response to adenosine diphosphate (ADP), epinephrine (Epi), or arachidonic acid (AA) and showed shape change only in response to collagen (Coll). Platelets from LD agglutinated reversibly with high-dose ristocetin.