The unusual pattern of hereditary bleeding disorders in the province of Newfoundland and Labrador-Canada's most Eastern Province.

Newfoundland and Labrador (NL), the most eastern province of Canada, is characterized by a unique topography and pattern of settlement. The current population is descended from a small founding population of indigenous Innu, Inuit and Mi'kmaq and an estimated 28,000 settlers. These settlers originated from Southwest England and Southeast Ireland and came to invest and work in one of the world's richest fisheries. They settled in bays, coves and islands off the coast, in small settlements called out-ports. These isolated communities developed unusual patterns of genetic disease including an unusual prevalence of some extremely rare Hereditary Bleeding Disorders (HBD). This study was designed to document the prevalence of these rare disorders, at a snapshot in time, using our provincial HBD registry. These diagnoses were verified by reviewing the original initial diagnostic coagulation results to confirm or refute each diagnosis. When available, we also recorded the underlying mutation. Population based prevalence rates were then compared with data published from the World Federation of Hemophilia (WFH) Global Registry. The results are striking. Using the WFH data the per capita prevalence in NL of Hemophilia A, Factors V, XI, and XIII Deficiency are higher than that of mainland Canada minus Labrador by a factor of 2.89, 4.54, 5.44 and 9.22, respectively. The increased prevalence of mild Hemophilia A is explained by a founder effect of the Val 2016 Ala mutation. All the severe FXIII deficient patients are homozygotes for c.691-1 G > A mutation. These results show that NL's unique geography and population distribution led to a genetic drift that increased the prevalence of some rare factor deficiencies. This comparatively high prevalence provides a potential pool of patients for genotype/phenotype research.

Characterization of aberrant splicing of von Willebrand factor in von Willebrand disease: an underrecognized mechanism.

Approximately 10% of von Willebrand factor (VWF) gene mutations are thought to alter messenger RNA (mRNA) splicing through disruption of consensus splice sites. This mechanism is likely underrecognized and affected by mutations outside consensus splice sites. During VWF synthesis, splicing abnormalities lead to qualitative defects or quantitative deficiencies in VWF. This study investigated the pathologic mechanism acting in 3 von Willebrand disease (VWD) families with putative splicing mutations using patient-derived blood outgrowth endothelial cells (BOECs) and a heterologous human embryonic kidney (HEK 293(T)) cell model. The exonic mutation c.3538G>A causes 3 in-frame splicing variants (23del, 26del, and 23/26del) which cannot bind platelets, blood coagulation factor VIII, or collagen, causing VWD through dominant-negative intracellular retention of coexpressed wild-type (WT) VWF, and increased trafficking to lysosomes. Individuals heterozygous for the c.5842+1G>C mutation produce exon 33 skipping, exons 33-34 skipping, and WT VWF transcripts. Pathogenic intracellular retention of VWF lacking exons 33-34 causes their VWD. The branch site mutation c.6599-20A>T causes type 1 VWD through mRNA degradation of exon 38 skipping transcripts. Splicing ratios of aberrant transcripts and coexpressed WT were altered in the BOECs with exposure to shear stress. This study provides evidence of mutations outside consensus splice sites disrupting splicing and introduces the concept that VWF splicing is affected by shear stress on endothelial cells.

Idiopathic venous thromboembolism and malignant disease: a case report.

BACKGROUND: The association between cancer and venous thromboembolism (VTE) is well known. Patients with idiopathic VTE have an increased risk of occult malignancy or subsequent development of cancer, compared with secondary VTE. CASE: A 43-year-old woman presented with idiopathic deep vein thrombosis (DVT) and menorrhagia. She had a history of hereditary non-polyposis colon cancer (HNPCC). One year later, investigations for persistent menorrhagia revealed uterine adenocarcinoma. CONCLUSION: Although there is no evidence that invasive screening for malignancy improves survival, recent findings have suggested that a directed search, based on family history, suspicious physical findings, or abnormal routine blood work, may be appropriate to rule out malignancy in women who present with VTE.

Acquired hemophilia a presenting as a bleeding diathesis in a postpartum patient: diagnosis and management.

Antibodies against Factor VIII (FVIII) can develop in non-hemophiliac patients, causing the rare condition of acquired hemophilia. In 7.3% of the patients, the FVIII inhibitors appear either during pregnancy or in the postpartum period. In this case report, we present a non-hemophiliac patient, who presented five months postpartum with intermittent heavy vaginal bleeding, easy bruising, hemarthrosis, and recurrent frank hematuria. The woman presented to the emergency room with hematuria. Coagulation screening tests showed a prolonged APTT. Using a standard diagnostic algorithm, a Factor VIII inhibitor was detected. The treatment, cause of disease, and prognosis of this woman is presented in this paper as well as a literature review of acquired hemophilia A associated with pregnancy.

Recombinant factor IX recovery and inhibitor safety: a Canadian post-licensure surveillance study.

As part of the Canadian post-licensure surveillance on the safety of recombinant factor IX (rFIX. BeneFIX), factor IX recovery and inhibitor development were studied. The recovery following rFIX infusion in 126 patients (mean = 0.77, median 0.72, range 0.36-1.85, 95% CI of mean 0.74-0.81, expressed as FIX activity increase in U/dL per IU FIX concentrate/kg body weight infused) was significantly lower than that following the last plasma-derived factor IX (pdFIX) infusion in 74 patients (mean 1.05, median 1.00, range 0.37-2.29, 95% CI of mean 0.99-0.97). The recovery for rFIX for patients aged < or =15 years (n = 41, mean recovery 0.64) and that for patients aged >15 years (n = 85, mean 0.84) was each significantly lower than that for pdFIX (aged < or =15 years: n = 21, mean recovery 0.91; aged >15 years: n = 53, mean recovery 1.10). For both rFIX and pdFIX concentrates, the recovery was lower in patients < or =15 years of age compared to those > 15 years of age. Similar data and conclusions were obtained on 66 patients with paired recovery data from rFIX and pdFIX. Overall, our data are similar to those obtained in formal clinical trials. Two of 244 patients treated with rFIX for up to 5 years have developed de novo inhibitors associated with anaphylaxis, an incidence that is similar to that reported for pdFIX. No other serious adverse events, including thrombotic episodes, were reported. To the best of our knowledge, this is the first formal report of recovery and inhibitor formation on rFIX in a peer-reviewed manuscript form.