Antibodies to factor XII: a possible predictive marker for recurrent foetal loss

Elevated plasma FXII is associated with disease activity in ANCA-associated vasculitis: A Retrospective Cross-Sectional Study in Western China

This study examined whether plasma FXII levels reflect disease activity in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Plasma FXII levels were detected by ELISA in 127 patients with AAV, and their associations with disease activity and plasma myeloperoxidase (MPO)-ANCA titre were examined. Immunofluorescent co-staining of FXII and neutrophils was performed on the renal tissues of patients with AAV. MPO expression in renal biopsy tissues was determined by immunohistochemical staining. The association between plasma FXII levels and histological activity was assessed in 82 patients who underwent kidney biopsy. Plasma FXII levels were considerably increased in patients with clinically active AAV compared to those in clinical remission and healthy individuals. Plasma FXII levels correlated positively with creatinine (r = 0.377), CRP (r = 0.222), urine red blood cell (r = 0.203), serum MPO-ANCA titer (r = 0.353), white blood cell (r = 0.194), percentage of glomeruli with crescents (P = 0.001), capillary breaks (P = 0.001), interstitial inflammation (P < 0.001) and fibrinoid necrosis (p < 0.001) on kidney biopsy. The plasma FXII optimal cut-off value for evaluating AAV activity was 24.5 μg/mL (sensitivity = 0.81, specificity = 0.82, P = 0.0001), which was superior to that achieved using conventional serologic biomarkers. Co-expression of FXII and neutrophils was higher, with increased MPO expression, in renal tissue with pathologically active AAV than that observed in pathologically inactive tissues. In conclusion, elevated plasma FXII levels reflect AAV clinical and histologic activity, and can serve as markers of active AAV.

Recurrent Miscarriage Syndrome and Infertility Due to Blood Coagulation Protein/Platelet Defects: A Review and Update

Three-hundred fifty-one women were referred for thrombosis and hemostasis evaluation after suffering recurrent miscarriages. All patients were referred by a high-risk obstetrician or reproductive medicine specialist after anatomic, hormonal or chromosomal defects had been ruled out. These patients were assessed over a three year period. The mean patient age at referral was 34 years and the mean number of miscarriages was 2.9 (2-9). All patients underwent a thorough evaluation for thrombophilia and, when indicated, a hemorrhagic disorder. Of the 351 patients, 29 (8%) had no defect. Of the remaining 322 patients, 7 (2%) had a bleeding disorder: 3 with platelet dysfunction, 1 with Factor XIII deficiency, 3 with von Willebrand’s and 3 with Osler-Weber-Rendu. The remainder of the patients had a thrombophilia as follows: 195 (60%) had antiphospholipid syndrome, 64 (20%) had Sticky Platelet Syndrome, 38 (12%) had MTHFR mutation, 23 (7.1%) had PAI-1 polymorphism, 12 (3.7%) had Protein S deficiency, 12 (3.7%) had Factor V Leiden, 3 (1%), had AT deficiency, 3 (1%) had Heparin-Cofactor II deficiency, 3 (1%) had TPA deficiency, and 6 (2%) had Protein C deficiency. There were a total of 364 defects found in the 312 patients harboring thrombophilia; thus, several harbored two and a few harbored three separate defects. All patients with thrombophilia were treated with preconception ASA at 81 mg/day with the immediate post-conception addition of heparin or LMW heparin (Dalteparin). Both ASA and heparin/LMW heparin were used to term. The first 120 patients were treated with unfractionated heparin at 5,000 U every 24 hours, subcutaneously and the last 192 have been treated with Dalteparin at 5,000 U/day subcutaneously. The patients with MTHFR were also treated with folate at 5 mg/day + pyridoxine at 50 mg/day. All patients were carefully monitored with CBC and platelet counts, anti-Xa levels, frequent ultrasounds and physical exams. Only 2 of the thrombophilia patients suffered another miscarriage; all others had a normal term delivery. There were no pregnancy-related thromboses, no delivery complications and no episodes of post-partum thrombosis. The only bleeding consisted of 1-4 cm bruises at injection sites. No episodes of thrombocytopenia (HIT) were noted. In our experience, thrombophilia is a common cause of recurrent miscarriage and all patients with no anatomical, hormonal or chromosomal defect should be evaluated for thrombophilia or a bleeding disorder. The success rate of normal term delivery in these 312 patients was 94% using ASA + heparin or Dalteparin. In addition, side effects of therapy were minimal.

Factor XII (Hageman) levels in women with recurrent pregnancy loss

Objective. To evaluate factor XII levels in women with recurrent pregnancy loss (RPL) in a tertiary referral hospital. Methods. Women who were referred to our hospital for two consecutive abortions or three abortions in between 2007 and 2013 were included in this retrospective observational study. Women were further grouped according to factor XII levels, as <60% and ≥60%. Results. Mean factor XII level was 109.1 ± 35.7% (range: 9–200). Ninety-three (7.4%) women had factor XII levels < 60%. Mean factor XII level was 44.8 ± 13.1, and levels ranged between 9 and 60 in this group. Only one woman had factor XII level < 10 %. Remaining 1164 (92.6%) women had factor XII levels ≥ 60%. Mean factor XII level was 114.3 ± 31.7, and levels ranged between 60.3 and 200 in this group, while 1015 (72.4%) women had factor XII levels within the normal range (60%–150% [100% = 30 μg/mL]). Conclusion. Decreased activity of F-XII was diagnosed in 7.4% of women with RPL. We concluded factor XII deficiency that might be a rare but significant factor for RPL, and should be evaluated in women who are investigated for recurrent pregnancy loss.

Coagulation factor deficiency as a cause of recurrent fetal loss: a red herring!

Whether severe coagulation factor deficiency can cause adverse pregnancy outcomes or recurrent fetal loss is not definitely known. We report here on five women with severe deficiency of coagulation factors (two factor X, one factor XI, one factor VII and one von Willebrand factor) who presented with history of unexplained fetal loss or with adverse pregnancy outcome. Detailed investigations of thrombophilia showed that four patients were positive for antiphospholipid antibodies, one of whom was also homozygous for the plasminogen-activator inhibitor-1 4G/4G polymorphism, and the fifth patient was deficient for protein C. Despite the concomitant presence of both coagulation factor defect and thrombophilia, fetal loss may be attributed to factor defect that in reality is a red herring, with underlying thrombophilia not being evaluated.

Factor XII autoantibodies as a novel marker for thrombosis and adverse obstetric history in patients with systemic lupus erythematosus

AIM

To investigate the clinical significance of anti-factor XII (FXII) in a large cohort of patients with systemic lupus erythematosus (SLE).

PATIENTS AND METHODS

This study comprised 127 patients with SLE. IgG and IgM anti-FXII were tested by an in-house ELISA. 123 healthy donors comprised the control group.

RESULTS

51 (40%) patients with SLE and 9 (7%) healthy controls were positive for anti-FXII. IgG and IgM anti-FXII were frequently found in patients with thrombosis (28% and 13%, respectively). Levels of IgG and IgM anti-FXII were higher in patients with thrombosis than in the control group (p<0.001 and p=0.005, respectively). Anti-FXII was more frequent in patients with arterial thrombosis (31% vs 4% for IgG and 14% vs 3% for IgM, respectively) and venous thrombosis than in controls (37% vs 4% for IgG). IgG anti-FXII were more frequent in patients with miscarriages and fetal death (35% and 40% vs 4% for IgM). The prevalence of IgM anti-FXII was not different between groups.

CONCLUSION

Anti-FXII are frequent in patients with SLE. Their presence is associated with thrombosis and adverse obstetric history, making these antibodies a novel marker for the antiphospholipid syndrome.

Acquired factor XII deficiency in a woman with recurrent pregnancy loss: working on a differential diagnosis in a single case

Background

Antiphospholipid syndrome (APS) has been often associated to RPL since 1980 and some reports in the Literature rarely described antibodies to factor XII in patients with APS.

Case history

We report the case history of 34-year-old caucasian women with recurrent fetal loss and persistent prolonged activated partial thromboplastin time. Haemostatic tests revealed persistent light decrease of clotting factor XII with normal values of IgG and IgM anticardiolipin antibodies and transient positivity for lupus anticoagulant (LA). Few reports in the Literature described antibodies to factor XII in patient with antiphospholipid syndrome (APS) and transient LA. So, once other causes of RPL were excluded, the patient was diagnosed an unusual form of APS associated to antibodies to factor XII, reduced factor XII plasma levels, transient LA and prolonged activated partial thromboplastin time.

Discussion

We suggest to consider also antibodies directed to clotting factors (e.g. factor XII in our case) as second step of thrombophilia screening in RPL, in particular if a persistent prolonged aPTT is present without an apparent cause.

The antigenic binding site(s) of antibodies to factor XII associated with the antiphospholipid syndrome

Phospholipid binding proteins, including factor XII (FXII), are known to be targeted by antiphospholipid antibodies (aPA). Factor XII antibodies (FXIIab) have been described in some patients with the antiphospholipid syndrome (APS) and have been shown to lead to reduced levels of FXII. The antigenic binding site(s) and the pathophysiological effects of FXIIab are unknown. In an attempt to elucidate the binding site of these antibodies, immobilized plasma kallikrein was used to cleave FXII into its 52-kDa heavy-chain (HCFXII) and 28-kDa light-chain (LCFXII) components. Plasma samples from 12 female patients with definite APS and FXIIab were investigated for the presence of antibodies to FXII, HCFXII and LCFXII. All but one patient's plasma reacted to FXII, HCFXII and LCFXII in a similar manner. One patient gave markedly reduced positivity to HCFXII and LCFXII, suggesting that the FXIIab in this patient had a higher affinity for the intact FXII molecule. To further investigate the antigenic binding site(s) of FXII, 150 biotinylated peptides of the known FXII sequence were synthesized using a Multipin(TM) peptide synthesis procedure. The IgG and IgM fractions of the 12 patients' plasma were purified by affinity chromatography. The synthesized peptides were captured on streptavidin plates and individual patients' purified FXIIab assayed against the peptides in a modified enzyme-linked immunosorbent assay (ELISA). Two regions were identified as possible antigenic binding site(s) for FXIIab: one in the growth factor domain and the other in the catalytic domain.