Quebec platelet disorder is linked to the urokinase plasminogen activator gene (PLAU) and increases expression of the linked allele in megakaryocytes.

Quebec platelet disorder (QPD) is an autosomal dominant disorder with high penetrance that is associated with increased risks for bleeding. The hallmark of QPD is a gain-of-function defect in fibrinolysis due to increased platelet content of urokinase plasminogen activator (uPA) without systemic fibrinolysis. We hypothesized that increased expression of uPA by differentiating QPD megakaryocytes is linked to PLAU. Genetic marker analyses indicated that QPD was significantly linked to a 2-Mb region on chromosome 10q containing PLAU with a maximum multipoint logarithm of the odds (LOD) score of +11 between markers D10S1432 and D10S1136. Analysis of PLAU by sequencing and Southern blotting excluded mutations within PLAU and its known regulatory elements as the cause of QPD. Analyses of uPA mRNA indicated that QPD distinctly increased transcript levels of the linked PLAU allele with megakaryocyte differentiation. These findings implicate a mutation in an uncharacterized cis element near PLAU as the cause of QPD.

Bleeding risks associated with inheritance of the Quebec platelet disorder.

Quebec platelet disorder (QPD) is an autosomal dominant bleeding disorder associated with increased urokinase-type plasminogen activator in platelets and alpha-granule protein degradation. To determine bleeding risks and common manifestations of QPD, a history questionnaire was developed and administered to 127 relatives in a family with QPD. Data entry was done blinded to affected and unaffected status, determined by assays for platelet urokinase-type plasminogen activator (u-PA) and fibrinogen degradation. Odds ratios (ORs), with 95% confidence intervals (CIs), were determined for items queried. Summative bleeding scores for each individual were calculated using items with OR more than 1. Mean ages (34 years; range, 1-89 years) were similar for affected (n = 23) and unaffected (n = 104) family members. Affected individuals had higher mean bleeding scores (P <.0001) and a much higher likelihood (OR > 20) of having bleeding that led to lifestyle changes, bruises that spread lower or as large or larger than an orange or both, joint bleeds, bleeding longer than 24 hours after dental extractions or deep cuts, and received or been recommended other treatments (fibrinolytic inhibitors) for bleeding. Individuals with QPD and exposure(s) to hemostatic challenges had experienced excessive bleeding only when fibrinolytic inhibitors had not been used. These data illustrate that QPD is associated with increased risks of bleeding that can be modified by fibrinolytic inhibitors.