Concurrence of von Willebrand's disease and hemophilia A: implications for carrier detection and prevalence

Familial multiple coagulation factor deficiencies - chance associations and distinct clinical disorders

The familial multiple coagulation factor deficiencies (FMCFDs) are a group of rare haemostatic disorders of genetic origin in which there is reduced plasma activity of more than one coagulation factor. FMCFDs may arise from co-incidental inheritance of separate coagulation factor deficiencies or from a single genetic or cytogenetic defect. All the FMCFDs present significant challenges in diagnosis and management yet there is little systematic evidence with which to guide clinical practice. This review summarizes the historical literature that describes the FMCFDs and introduces a refined classification of these disorders. The clinical and laboratory characteristics of the most common FMCFDs are considered in detail.

Combined clotting factor deficiencies: experience at a single hemophilia treatment center

We describe a series of patients with combined factor deficiencies and von Willebrand's disease (VWD) at one haemophilia treatment centre. Although the incidence of VWD is at least 1% in the general population, combined coagulation defects have been infrequently described in the medical literature and are likely under diagnosed. This entity should be considered in patients with a known factor deficiency and either an unexpectedly severe bleeding phenotype, or bleeding that is unresponsive to factor replacement.

Diagnosis of von Willebrand disease type 2N: a simplified method for measurement of factor VIII binding to von Willebrand factor

Diagnosis of von Willebrand disease Type 2N (vWD 2N), which mimics hemophilia A and its carrier state, is important for accurate genetic counseling and appropriate therapy. To make testing for the disorder more clinically applicable, we developed a simplified method for measurement of factor VIII (FVIII) binding to von Willebrand factor (vWF) using commercially available reagents and standard clinical assays. FVIII binding to vWF was measured by capture of patient vWF by polyclonal antibodies on cyanogen bromide-activated Sepharose beads, reaction with recombinant FVIII, and assay of unbound FVIII by clotting methods. Unbound vWF was measured in patient plasma after capture by the Laurell method. The ratio of bound FVIII/bound vWF was normal in hemophilia A, vWD Type 1, and vWD Type 3 patients, and abnormal in 5 subjects from two families, all of whom had vWD 2N mutations. Patient 1, with FVIII 8 U/dl, vWF: Ag 61 U/dl, vWF:RC 74 U/dl, and FVIII binding nil, was homozygous for the Arg91 Gln mutation. She was followed during pregnancy and delivered an unaffected heterozygous son. Patient 2 had FVIII 8 U/dl, vWF:Ag 73 U/dl, and vWF:RC 71 U/dl, and very low FVIII binding. She was heterozygous for Arg91Gln, as were her mother and sister; no second vWD 2N mutation was found. Her brother, with FVIII 14 U/dl, vWF:Ag 113 U/dl, and vWF:RC 72 U/dl, has no evidence of vWD 2N. With an X-linked inheritance pattern of bleeding tendency, this family is the first reported with combined hemophilia A and vWD 2N.

Haemophilia A: carrier detection by DNA analysis

From 46 families of predominantly German origin, afflicted with haemophilia A, 178 females were tested for carrier status. Two polymorphic restriction endonuclease sites, the extragenic marker locus DXS 52 (St 14 probe) and the intragenic Bcl I RFLP were investigated in these families. In some cases the results were corroborated by identifying (i) deletions within the factor VIII:C gene and (ii) eliminating a restriction endonuclease site. Two new alleles of the DXS 52 marker locus were found. According to this strategy, 27 women were classified as carriers and 74 as non-carriers. Forty-six women were classified as carriers according to pedigree analysis. Twenty-five females of families with sporadic cases and 6 test persons, who had mothers who where homozygous for the marker alleles, were diagnosed by additional use of conventional carrier detection.

Reproductive choices in hemophilic men and carriers

We have examined reproduction patterns in hemophilic men and carrier women seen at a hemophilia treatment center. The study group included 309 patients with hemophilia A or B: 194 adults and 115 children from 246 pedigrees; 93% of affected men and 96% of parents of affected children had received genetic counseling. In the collected pedigrees, 65% of affected males were born to women with family history of hemophilia. An additional 23% of mothers were later shown to be carriers. Fewer than 12% of cases could be due to a new mutation in the child. Among 209 hemophilia A carrier tests, 95% of obligate carriers were detectable, 87% of mothers of sporadic cases, 53% of sisters of hemophiliacs, and 24% of other relatives had a high risk of carriership. Of 49 high-risk women seen during or prior to pregnancy, one-half elected prenatal diagnosis. Amniocentesis was performed in 24 cases and 8 were referred for fetoscopy, resulting in 18 normal offspring. Among 25 pregnancies not tested, 14 continued and produced 3 affected males and 11 normal offspring. Of hemophilic men over age 25, 66% have married and 41% (62% of those married) have had children. These observations will serve as a baseline for assessing any change in reproductive patterns occurring with the introduction of new genetic techniques.