Investigation of a common canine factor VII deficiency variant in dogs with unexplained bleeding on autopsy.

The factor VII (FVII) protein is an integral component of the extrinsic coagulation pathway. Deleterious variants in the gene encoding this protein can result in factor VII deficiency (FVIID), a bleeding disorder characterized by abnormal (slowed) clotting with a wide range of severity, from asymptomatic to life-threatening. In canids, a single FVIID-associated variant, first described in Beagles, has been observed in 24 breeds and mixed-breed dogs. Because this variant is present in breeds of diverse backgrounds, we hypothesized that it could be a contributing factor to unexplained bleeding observed in some canine autopsy cases. DNA was extracted from paraffin-embedded tissue samples from 67 anticoagulant-negative autopsy cases with unexplained etiology for gross lesions of hemorrhage. Each dog was genotyped for the c.407G>A (F71) variant. Experimental controls included 3 known heterozygotes and 2 known homozygotes for the F71 variant, 2 normal dogs with known homozygous wild-type genotypes (F7WF7W), and 5 dogs with bleeding at autopsy that tested positive for anticoagulant rodenticide and were genotyped as F7WF7W. All 67 cases tested homozygous for the wild-type allele, indicating that the common FVIID variant was not responsible for the observed unexplained bleeding. Our work demonstrates the usefulness of retrospective studies utilizing veterinary diagnostic laboratory databases and tissue archives for genetic studies. In the case of FVIID, our results suggest that a singular molecular test for the F71 variant is not a high-yield addition to postmortem screening in these scenarios.

Canine factor VII deficiency: lessons learned in applying methods-based laboratory proficiency testing.

Canine inherited factor VII deficiency is a mild-to-moderate, inherited coagulopathy that affects several breeds of dog. We identified 2 polymorphisms near the disease-causing F7 gene mutation, one of which interfered with testing in several Beagles by causing allele dropout of the normal, wild-type allele. In the absence of an external proficiency program among veterinary genetic testing laboratories, implementation of an internal proficiency program, which requires 2 independent methods for genotyping dogs at any given locus, was further enhanced by ensuring minimally non-overlapping primer pairs between the 2 assays. After redesign of our clinical tests, all dogs were re-examined, and the correct genotypes were identified. These changes ensure higher accuracy in future testing of the F7 mutation.

Outcome of laparoscopic ovariohysterectomy or ovariectomy in dogs with von Willebrand disease or factor VII deficiency: 20 cases (2012-2014).

OBJECTIVE To describe surgical techniques and perioperative management of dogs with von Willebrand disease (VWD) or factor VII (FVII) deficiency undergoing laparoscopic ovariohysterectomy or ovariectomy and evaluate outcomes. DESIGN Retrospective case series. ANIMALS 20 client-owned dogs with VWD (n = 16) or FVII deficiency (4). PROCEDURES Dogs with VWD or FVII deficiency that underwent laparoscopic ovariohysterectomy or ovariectomy between 2012 and 2014 were retrospectively identified via a multi-institutional review of medical records. RESULTS Median expression of von Willebrand factor was 19% (interquartile range, 18% to 30%). All 16 dogs with VWD were Doberman Pinschers, and all were pretreated with desmopressin; 4 also received cryoprecipitate. One of 4 dogs with FVII deficiency received plasma preoperatively, and 1 was treated with desmopressin; 2 dogs received no preoperative treatment. Laparoscopic ovariectomy was performed in 9 dogs with VWD and 2 dogs with FVII deficiency, laparoscopic ovariectomy with gastropexy was performed in 6 dogs with VWD and 1 dog with FVII deficiency, and laparoscopic-assisted ovariohysterectomy was performed in 1 dog with VWD and 1 dog with FVII deficiency. Iatrogenic splenic laceration requiring conversion to laparotomy occurred during trocar insertion in 1 dog with VWD. No postoperative complications, including signs of hemorrhage, were reported for any dogs. CONCLUSIONS AND CLINICAL RELEVANCE Laparoscopic ovariohysterectomy or ovariectomy in dogs with VWD or FVII deficiency pretreated with desmopressin, cryoprecipitate, or plasma transfusions were not associated with clinical signs of hemorrhage, suggesting that minimally invasive ovariohysterectomy or ovariectomy may be considered in female dogs affected with these coagulopathies.

HEREDITARY FACTOR VII DEFICIENCY IN THE ASIAN ELEPHANT (ELEPHAS MAXIMUS) CAUSED BY A F7 MISSENSE MUTATION.

Hereditary disorders and genetic predispositions to disease are rarely reported in captive and free-ranging wildlife, and none have been definitively identified and characterized in elephants. A wild-caught, 41-yr-old male Asian elephant ( Elephas maximus ) without an apparent increased bleeding tendency was consistently found to have prolonged prothrombin times (PTs, mean=55±35 s) compared to 17 other elephants (PT=10±2 s). This elephant's partial thromboplastin times (PTT) fell within the normal range of the other elephants (12-30 s). A prolonged PT in the presence of a normal PTT suggests disruption of the extrinsic pathway via deficiency of coagulation Factor VII (FVII). This elephant's plasma FVII activity was very low (2%) compared to that of 15 other elephants (57-80%), but other coagulation factors' activities did not differ from the control elephants. Sequencing of genomic DNA from ethylenediaminetetraacetic acid blood revealed a single homozygous point mutation (c.202A>G) in the F7 gene of the FVII deficient elephant that was not present in unrelated elephants. This mutation causes an amino acid substitution (p.Arg68Gly) that is predicted to be deleterious. Two living offspring of the affected elephant were heterozygous for the mutation and had normal plasma FVII activities and coagulation profiles. Tissue from a third offspring, a deceased calf, was utilized to show that it was also a heterozygote. A DNA test has been developed to enable the screening of additional elephants for this mutation. Consistent with FVII deficiency investigations in other species, the condition did not cause a serious bleeding tendency in this individual elephant.

Canine specific ELISA for coagulation factor VII.

Canine coagulation factor VII (FVII) deficiency can be hereditary or acquired and may cause life threatening bleeding episodes if untreated. FVII procoagulant activity can be measured by FVII activity (FVII:C), but assays for measurement of canine specific FVII antigen (FVII:Ag) have not been available to date. In this study, a canine specific ELISA for measurement of FVII:Ag in plasma was developed and validated. The FVII:Ag ELISA correctly diagnosed homozygous and heterozygous hereditary FVII deficiency. Together with activity based assays, such as FVII:C, the FVII:Ag ELISA should be valuable in the diagnosis of hereditary canine FVII deficiency.

Inadvertent propagation of factor VII deficiency in a canine mucopolysaccharidosis type I research breeding colony.

Issues of cost and genetics can result in inbreeding of canine genetic disease colonies. Beagles often are used to maintain such colonies, providing stock for outcrosses. Factor VII (FVII) deficiency is a hemostatic disorder found at increased frequency in beagles and has been characterized at the DNA level. Deficiency of FVII presents obstacles in colonies founded with beagles. An initial finding of a FVII-deficient pup from a longstanding colony prompted us to evaluate FVII deficiency fully in this colony. Current and archival records and tissues were used to reconstruct the colony pedigree, assess the contribution from beagles, and test samples to document the source and frequency of the mutant FVII allele. As part of this study we developed a PCR-based diagnostic assay that was simpler than what was previously available. Pedigree analysis revealed a founder effect implicating beagles that led to high frequency (55%) of the mutant allele. In addition, affected animals were identified. The complete picture of the clinical effect within the colony remains unclear, but unusual neonatal presentations, including hemoabdomen, have occurred in pups affected with FVII deficiency. Use of a PCR-based diagnostic assay to screen all potential beagle breeding stock will prevent similar occurrences of FVII deficiency in future canine research colonies.

Hereditary factor VII deficiency in the Alaskan Klee Kai dog.

BACKGROUND: Hereditary factor VII (FVII) deficiency is characterized as a mild bleeding disorder in Beagles, caused by a missense mutation in exon 5 of the FVII gene. An Alaskan Klee Kai dog with severe bleeding after trauma was diagnosed with FVII deficiency based on coagulation testing. Molecular analyses were undertaken to identify the genetic basis of the defect in this breed. HYPOTHESIS: FVII deficiency in Alaskan Klee Kai dogs is caused by a mutation in the FVII gene. ANIMALS: Eighteen client-owned Alaskan Klee Kai. METHODS: Coagulation screening tests and factor assays were performed to characterize the coagulopathy. All coding regions of the propositus' FVII gene were sequenced. Amplification of exon 5, sequencing, and Mnl I restriction digest experiments were performed to screen for a point mutation in the remaining 17 dogs. RESULTS: FVII deficiency was diagnosed in 6 dogs with a median FVII activity (FVII: C) of 5% (reference range, 50 150%). All FVII-deficient Alaskan Klee Kai were homozygous for the same mutation as FVII-deficient Beagles (ie, a G to A transition), resulting in substitution of glycine 96 by glutamic acid. An overlap in the FVII: C values obtained from heterozygote and wild-type dogs precluded accurate detection of carriers without genetic screening. CONCLUSIONS AND CLINICAL IMPORTANCE: FVII deficiency may be associated with a bleeding tendency and should be considered in Alaskan Klee Kai dogs with prolonged prothrombin times. Plasma FVII: C accurately identifies affected dogs, but deoxyribonucleic acid testing is required for identification of carriers.

A novel missense mutation responsible for factor VII deficiency in research Beagle colonies.

BACKGROUND: Canine factor VII (cFVII) deficiency, an autosomal recessive trait originally identified in research Beagles, is associated with a mild to moderate bleeding tendency. OBJECTIVE: Our aim was to identify and characterize the mutation causing cFVII deficiency. METHODS: In order to sequence the coding regions of the cFVII gene, we cloned the cFVII cDNA. Genomic DNA and plasma from FVII-deficient Beagles and obligate carriers were utilized. RESULTS: In all FVII-deficient dogs, we identified a single causative G to A missense mutation in exon 5, encoding the second epidermal growth factor-like domain, resulting in substitution of glycine 96 by glutamic acid, with plasma FVII coagulant activity of

Factor VII deficiency in a mixed breed dog.

Abnormal bleeding following routine orchectomy of a 5-month-old mixed breed was determined to be due to factor VII deficiency. Although pedigree information was unavailable, failure to respond to vitamin K therapy and the absence of a plasma coagulation inhibitor suggested that the factor VII deficiency was likely inherited rather than acquired.

Optimization of prothrombin time measurements in canine plasma.

OBJECTIVE: To optimize a prothrombin time (PT) method designed for human plasma for use with canine plasma. SAMPLE POPULATION: 100 plasma samples from healthy dogs and 50 plasma samples with reduced activity of the single factors II, V, VII or X. PROCEDURE: Canine plasma samples with various coagulation activity values (100, 75, 50, 25 and 10%: prepared by dilution from a plasma pool [n = 100]) were assayed at various sample dilutions and dilutions of the thromboplastin component of 3 commercial calcium thromboplastin reagents. The sc-named optimized PT test was compared with the standard test with respect to its sensitivity and correlation with the sum of the activity decreases of single factors II, V, VII, and X in relation to the respective reference range. RESULTS: The time intervals between various coagulation activity values, which were small by use of the standard test, could be increased by diluting the sample and substituting fibrinogen, but not by diluting the tissue thromboplastin component of PT reagent. On the basis of 50 abnormal plasma samples, the optimized test had high sensitivity (0.90 to 1.00, dependent on reagent and sample dilution) in contrast to the standard test, which had low sensitivity (0.24 to 0.58, dependent on reagent). Also, correlation with the sum of the activity decreases was closer by use of the optimized (0.90 to 0.93) than the standard (0.58 to 0.84) test. CONCLUSIONS: In contrast to the standard test, an optimized test is suitable as a sensitive screening test of the extrinsic coagulation system in dogs. CLINICAL RELEVANCE: The optimized PT method is easy to perform and, therefore, should be in general use for assay of canine plasma.

Buccal mucosa bleeding time is prolonged in canine models of primary hemostatic disorders.

Bleeding times are reported in many studies using canine models, with a variety of techniques employed to adapt these tests for dogs. We evaluated a canine model of template bleeding time, the buccal mucosa bleeding time (BMBT), by examining the test's sensitivity and specificity for defects of primary hemostasis. We examined thirty-five dogs having defined defects of either primary hemostasis (Types I, II, III von Willebrand's disease, thrombasthenia, thrombopathia) or secondary hemostasis (hemophilia A and B, Factor VII deficiency). Comparisons of BMBT and cuticle bleeding time were made in a subset of these dogs. All dogs having primary hemostatic disorders had long BMBT, and all factor deficient dogs had BMBT within normal range. The BMBT in canine models appears to be a specific and sensitive test of primary hemostasis; suitable for evaluating factors affecting template bleeding time and potential efficacy and thrombogenicity of treatment regimens.

Vitamin K-dependent multifactor coagulopathy in Devon Rex cats.

A coagulopathy attributable to a deficiency of vitamin K-dependent clotting factors (II, VII, IX, and X) was diagnosed in 3 Devon Rex cats. There was no evidence for exposure to vitamin-antagonist-related rodenticides. The cats did not have evidence of hepatic disease, gastrointestinal disease, or fat malassimilation. Oral treatment with vitamin K1 resulted in normalization of clotting factor concentrations. However, when treatment was discontinued in 2 cats, prothrombin and activated partial thromboplastin values became prolonged again, although the cats did not have clinical signs of a bleeding disorder.

Inherited coagulation disorders.

Inherited coagulation disorders have been diagnosed in many breeds of dogs as well as in mongrels and cats. This article presents the different coagulation factor deficiencies that are known to exist in small animals. A description is given of each coagulation factor along with the relevant clinical signs, inheritance, and the breeds affected. Suggestions are also given for the diagnosis and therapy of these deficiencies.

Hereditary blood coagulation factor-VII deficiency: a comparison of the defect in beagles from several sources.

1. Hereditary blood coagulation factor-VII deficiency has previously been identified in Beagles from a number of sources in Britain and North America. 2. A study is now reported in which the nature of the defect is compared in plasma samples from these sources. 3. When prothrombin times and Russell's Viper venom clotting times were determined on mixtures of samples, no cross-correction of the defective coagulation activity was detected. 4. Antibody neutralization assays of factor-VII related antigen and assays of factor-VII procoagulant activity revealed essentially similar levels in all samples. 5. Thus no significant genetic variants of the defect were identified.

[Congenital deficiency of factor VII in a canine family].

Prolonged prothrombin time in the blood coagulation test was seen in some beagle dogs whose activated partial prothrombin times were distributed within the normal range. This phenomenon suggested possible abnormalities in coagulation factors II, V, VII, and/or X. Therefore, a revised cross-matching test was given and a determination of coagulation factors related to the extrinsic system was performed. We also determined whether or not factor VII inhibitor was present. The results were as follows: 1) In the revised cross-matching test, the prolonged prothrombin times were revised when normal canine serum was added to the plasma that showed prolongation of prothrombin time, but not when pooled normal canine plasma absorbed with BaSO4 was added to it. 2) The level of factor VII in the plasma with prolonged prothrombin time was 5 approximately 10% of the level in normal canine plasma. 3) Factor VII inhibitor was not detected in the plasma with prolonged prothrombin time or in normal plasma. Consequently, the prolongation of prothrombin time was attributed to a deficiency in factor VII. This abnormality was confirmed to be congenital.

Automated synthetic substrate assays for coagulopathies of dogs.

Automated synthetic substrate assays for factors II and VII in the extrinsic coagulation pathway have been developed in our laboratory. In both kinetic assays, p-nitroaniline (pNA) was cleaved from the substrate and measured spectrophotometrically at 405 nm. Plasma samples from 5-8 month old beagle dogs were analyzed for factors II and VII, and also for prothrombin times. A subpopulation considered abnormal (prothrombin times greater than 8 seconds) had slightly elevated factor II levels, but extremely low factor VII levels, relative to the normal group. Therefore, the prolonged prothrombin times of this abnormal group can now be confidently attributed to their decreased factor VII levels. The known genetic predisposition of beagle dogs to factor VII deficiency supports this conclusion. Thus, synthetic substrates are useful for the measurement of coagulation factors in dogs, and permit ready automation of the assay.

Hereditary blood coagulation factor-VII deficiency in the beagle: immunological characterisation of the defect.

In the plasma of beagles known to be homozygotes for hereditary blood coagulation factor-VII deficiency, antibody neutralization assays indicate only slightly greater quantities of factor-VII related antigen than are detected by conventional assays of procoagulant activity. Plasma of one dog was depleted of factor-VII procoagulant activity by exposure to an immobilized antibody; the low level of activity originally present was then verified by titration with normal plasma. The plasma defect results from an incomplete deletion of synthesis.