ABSTRACT
BACKGROUND: Deficiency of natural anticoagulant antithrombin was first reported as a genetic risk factor for venous thromboembolism, antithrombin III (AT III) is encoded by the serpin family C member 1 (SERPINC1) gene, consisting of 432 amino acids, including 3 disulfide bonds and 4 possible glycosylation sites. Studies have shown that hereditary AT deficiency increases the incidence of venous thromboembolism by up to 20 times. CASE PRESENTATION: The case presented a 27-year-old young man with no acquired risk factors and a sudden onset of right lower extremity venous thrombosis and pulmonary embolism. A heterozygous mutation in gene SERPINC1 of c.1154-14G>A was detected in the patient, which is a deleterious mutation resulting in reduced AT III activity and increased risk of thrombotic events. The patient received anticoagulant therapy for approximately 5 months, and the thrombus gradually dissolved and no recurrent thrombotic events occurred during follow-up. DISCUSSION: AT deficiency is a rare autosomal dominant genetic disease, they are mainly divided into 2 types according to the different effects on the structure or function of the encoded protein. The patient had a mutation in the SERPINC1 gene (c.1154-14G>A). Several cases of this type of mutation have been reported since 1991, and it is classified as AT deficiency type I. CONCLUSION: Thrombosis in patients with antithrombin deficiency is often unpredictable and can lead to fatal pulmonary embolism. Early genetic testing for hereditary thrombophilia in venous thromboembolism patients without obvious high-risk factors is critical. Long-term anticoagulation treatment is an effective treatment, for this type of type I AT III deficiency combined with pulmonary embolism patients, warfarin is an effective anticoagulant drug.
Subject(s)
Antithrombin III , Mutation , Pulmonary Embolism , Humans , Pulmonary Embolism/genetics , Male , Adult , Antithrombin III/genetics , Antithrombin III Deficiency/genetics , Antithrombin III Deficiency/complications , Anticoagulants/therapeutic useSubject(s)
Liver Cirrhosis , Prothrombin , Thrombin , Humans , Prothrombin/metabolism , Liver Cirrhosis/blood , Thrombin/metabolism , Blood Coagulation , Antithrombin III Deficiency/blood , Antithrombin III Deficiency/complications , Antithrombin III Deficiency/diagnosis , Antithrombin III Deficiency/geneticsABSTRACT
RATIONALE: White matter lesions (WMLs) are structural changes in the brain that manifest as demyelination in the central nervous system pathologically. Vasogenic WMLs are the most prevalent type, primarily associated with advanced age and cerebrovascular risk factors. Conversely, immunogenic WMLs, typified by multiple sclerosis (MS), are more frequently observed in younger patients. It is crucial to distinguish between these 2 etiologies. Furthermore, in cases where multiple individuals exhibit WMLs within 1 family, genetic testing may offer a significant diagnostic perspective. PATIENT CONCERNS: A 25-year-old male presented to the Department of Neurology with recurrent headaches. He was healthy previously and the neurological examination was negative. Brain magnetic resonance imaging (MRI) showed widespread white matter hyperintensity lesions surrounding the ventricles and subcortical regions on T2-weighted and T2 fluid-attenuated inversion recovery images, mimicking immunogenic disease-MS. DIAGNOSES: The patient was diagnosed with a patent foramen ovale, which could explain his headache syndrome. Genetic testing unveiled a previously unidentified missense mutation in the SERPINC1 gene in the patient and his father. The specific abnormal laboratory finding was a reduction in antithrombin III activity, and the decrease may serve as the underlying cause for the presence of multiple intracranial WMLs observed in both the patient and his father. INTERVENTIONS: The patient received percutaneous patent foramen ovale closure surgery and took antiplatelet drug recommended by cardiologists and was followed up for 1 month and 6 months after operation. OUTCOMES: While the lesions on MRI remain unchanging during follow-up, the patient reported a significant relief in headaches compared to the initial presentation. LESSONS: This case introduces a novel perspective on the etiology of cerebral WMLs, suggesting that hereditary antithrombin deficiency (ATD) could contribute to altered blood composition and may serve as an underlying cause in certain individuals with asymptomatic WMLs.
Subject(s)
Antithrombin III Deficiency , Foramen Ovale, Patent , Multiple Sclerosis , Nervous System Diseases , Vascular Diseases , White Matter , Male , Humans , Adult , White Matter/diagnostic imaging , White Matter/pathology , Foramen Ovale, Patent/pathology , Antithrombin III/genetics , Antithrombin III Deficiency/complications , Antithrombin III Deficiency/genetics , Antithrombin III Deficiency/pathology , Brain/pathology , Magnetic Resonance Imaging/methods , Vascular Diseases/pathology , Nervous System Diseases/pathology , Multiple Sclerosis/diagnosis , Headache , Mutation , AntithrombinsABSTRACT
BACKGROUND: Thrombophilia is a coagulation disorder closely associated with venous thromboembolism. Hereditary antithrombin III (AT III) deficiency is a type of genetic thrombophilia. In China, genetic thrombophilia patients mainly suffer from deficiencies in AT III, protein S, and protein C. Multiple mutations in the serpin family C member 1 (SERPINC1) can affect AT III activity, resulting in thrombosis. CASE PRESENTATION: This case presented a 17-year-old adolescent female who developed lower extremity venous thrombosis and subsequently pulmonary embolism (PE) following a right leg injury. A missense mutation in gene SERPINC1 of c.331 Tâ >â C, p.S111P was detected on the patient, resulting in a decreased AT III activity and an elevated risk of thrombosis. The patient received anticoagulation treatment for approximately 5 months. During follow-up, the blood clot gradually dissolved, and there have been no recurrent thrombotic events reported thus far. DISCUSSION: Hereditary AT deficiency can be classified into two types based on the plasma levels of the enzymatic activity and antigen. Type I is a quantitative defect, while Type II is a qualitive defect. Until 2021, 486 SERPINC1 gene mutations have been registered, more than 18% of which are point mutations. The SERPINC1 mutation c.331 Tâ >â C in was firstly reported in 2017, which was classified into type I AT III deficiency. CONCLUSION: Hereditary thrombophilia is a coagulation disorder with a high omission diagnostic rate. Minor mutations in the SERPINC1 gene can also lead to hereditary AT III deficiency, which in turn can cause PE. We emphasized the importance of etiological screening for hereditary thrombophilia in venous thromboembolism patients without obvious high-risk factors. Long-term anticoagulation treatment and avoidance of potential thrombosis risk factors are critical for such patients.
Subject(s)
Antithrombin III Deficiency , Pulmonary Embolism , Thrombophilia , Thrombosis , Venous Thromboembolism , Adolescent , Humans , Female , Antithrombin III Deficiency/complications , Antithrombin III Deficiency/genetics , Venous Thromboembolism/genetics , Thrombosis/genetics , Pulmonary Embolism/genetics , Anticoagulants/therapeutic useABSTRACT
Hereditary antithrombin (AT) deficiency is a rare thrombophilia associated with cerebral vein thrombosis (CVT). We report a case study of hereditary AT deficiency causing CVT in three members of a family. A 29-year-old female presented with features of CVT. Her mother and a sister had CVT in the past and investigation for hereditary thrombophilia revealed low blood AT activity in all of them. The index patient (proband) was positive for the SERPINC1 gene mutation confirming the diagnosis of hereditary AT deficiency. She recovered well with anticoagulation and was advised to continue it lifelong. Diagnosing hereditary thrombophilia like AT deficiency is important in planning anticoagulation and proper counseling of asymptomatic family members regarding prophylaxis for venous thromboembolism (VTE) in high-risk situations.
Subject(s)
Antithrombin III Deficiency , Intracranial Thrombosis , Thrombophilia , Venous Thrombosis , Humans , Female , Adult , Antithrombin III Deficiency/complications , Antithrombin III Deficiency/genetics , Thrombophilia/drug therapy , Thrombophilia/genetics , Intracranial Thrombosis/etiology , Venous Thrombosis/etiology , Anticoagulants/therapeutic useABSTRACT
Literature regarding the management of thrombus refractory to first-line treatment in the setting of pregnancy is limited, and management is made even more complicated in the context of thrombophilia. This case reviews the management of a patient with antithrombin deficiency who developed a massive thrombus during pregnancy, which was complicated by May-Thurner syndrome, lack of improvement with heparin, and preterm labor. The patient received multidisciplinary care throughout the pregnancy. At 35 weeks, anticoagulation was paused as she underwent induction of labor and delivery followed by postpartum placement of inferior vena cava filter and restarting heparin. Successful management of our pregnant patient with thrombus refractory to heparin hinged on individualized treatment for medical optimization with anticoagulation and antithrombin concentrate prior to labor followed by immediate postpartum placement of inferior vena cava filter.
Subject(s)
Antithrombin III Deficiency , May-Thurner Syndrome , Vena Cava Filters , Venous Thrombosis , Pregnancy , Female , Infant, Newborn , Humans , Venous Thrombosis/complications , Venous Thrombosis/drug therapy , May-Thurner Syndrome/complications , Peripartum Period , Antithrombin III Deficiency/complications , Antithrombin III Deficiency/drug therapy , Heparin/therapeutic use , Anticoagulants/therapeutic use , Antithrombins , Vena Cava Filters/adverse effects , Vena Cava, InferiorABSTRACT
Antithrombin (AT) deficiency is a high-risk thrombophilia and a rare condition. The risk of venous thromboembolism (VTE) is increased in AT-deficient women during pregnancy and the postpartum period and is especially high in women with a prior history of VTE. A thorough assessment of VTE risk is recommended in pregnant AT-deficient women, comprising the degree and type of AT deficiency, genetic mutations, personal and family history, and additional preexisting or pregnancy-specific risk factors. Due to a lack of adequate study data, there is limited guidance on the management of AT deficiency in pregnancy, including the need for prophylactic anticoagulation, the appropriate dose of low-molecular-weight heparin (LMWH), and the role of AT substitution. LMWH is the medication of choice for the pharmacological prophylaxis and treatment of VTE in pregnancy. Patients with a history of VTE should receive full-dose LMWH during pregnancy and the postpartum period. AT concentrates are a treatment option when anticoagulation is withheld in potentially high-risk events such as childbirth, bleeding, or surgery and in cases of acute VTE despite the use of therapeutic dose anticoagulation. Women with AT deficiency should be counseled at specialized centers for coagulation disorders or vascular medicine, and close cooperation between obstetricians and anesthesiologists is warranted before delivery and during the peripartum period.
Subject(s)
Antithrombin III Deficiency , Venous Thromboembolism , Pregnancy , Humans , Female , Heparin, Low-Molecular-Weight/therapeutic use , Venous Thromboembolism/diagnosis , Venous Thromboembolism/drug therapy , Venous Thromboembolism/prevention & control , Antithrombin III Deficiency/complications , Antithrombin III Deficiency/diagnosis , Antithrombin III Deficiency/drug therapy , Anticoagulants/therapeutic use , Antithrombins/therapeutic use , Risk FactorsABSTRACT
RATIONALE: Inherited antithrombin deficiency (ATD) is a major cause of thrombotic deficiency. Genetic testing is of great value in the diagnosis of hereditary thrombophilia. Herein, we report a case of inherited ATD admitted to our hospital. We include the results of genealogy and discuss the significance of genetic testing in high-risk groups of hereditary thrombophilia. PATIENT CONCERNS: A 16-year-old male patient presented with chest tightness, shortness of breath, wheezing, and intermittent fever (up to 39 °C) after strenuous exercise for 2 weeks. He also had a cough with white sputum with a small amount of bright red blood in the sputum and occasional back pain. DIAGNOSES: The blood tests showed that the patient's antithrombin III concentration and activity were both significantly reduced to 41% and 43.2%, respectively. Enhanced chest computed tomography scans showed pulmonary infarction in the lower lobe of the right lung with multiple embolisms in the bilateral pulmonary arteries and branches. Lower vein angiography revealed a contrast-filling defect of the inferior vena cava and left common iliac vein. Thrombosis was considered as a differential diagnosis. His father and his uncle also had a history of thrombosis. The patient was diagnosed with inherited ATD. Further, peripheral venous blood samples of the family members were collected for whole-exome gene sequencing, and Sanger sequencing was used to verify the gene mutation site in the family. The patient and his father had a SERPINC1 gene duplication mutation: c.1315_1345dupCCTTTCCTGGTTTTTAAGAGAAGTTCCTC (NM000488.4). INTERVENTIONS: An inferior vena cava filter was inserted to avoid thrombus shedding from the lower limbs. Urokinase was injected intermittently through the femoral vein cannula for thrombolysis. Heparin combined with warfarin anticoagulant therapy was sequentially administered. After reaching the international normalized ratio, heparin was discontinued, and oral warfarin anticoagulant therapy was continued. After discharge, the patient was switched to rivaroxaban as oral anticoagulation therapy. OUTCOMES: The patient's clinical symptoms disappeared. reexamination showed that the thrombotic load was less than before, and the inferior vena cava filter was then removed. LESSONS: By this report we highlight that gene detection and phenotypic analysis are important means to study inherited ATD.
Subject(s)
Antithrombin III Deficiency , Thrombophilia , Thrombosis , Male , Humans , Adolescent , Warfarin/therapeutic use , Antithrombin III Deficiency/complications , Antithrombin III Deficiency/genetics , Antithrombin III Deficiency/drug therapy , Thrombophilia/drug therapy , Vena Cava, Inferior , Anticoagulants , Heparin , Mutation , Thrombosis/drug therapy , Antithrombins , Antithrombin III/geneticsABSTRACT
Antithrombin deficiency is a high-risk factor for venous thromboembolism during pregnancy, whereas cerebral venous thrombosis is rare. Cerebral venous thrombosis related to coronavirus disease 2019 (COVID-19) vaccines has been reported; however, there are a few reports of cerebral venous thrombosis after a messenger RNA (mRNA) vaccination. A 25-year-old female in her sixth week of pregnancy presented with headache 24 days after BNT162b2 mRNA COVID-19 vaccination. The following day, she presented with altered sensorium and was diagnosed with severe cerebral venous thrombosis. She demonstrated heparin resistance and was found to have an inherited antithrombin deficiency. A heterozygous missense variant in SERPINC1 (c.379T>C, p.Cys127Arg, 'AT Morioka') was detected by DNA analysis. Despite intensive care with unfractionated heparin, antithrombin concentrate, and repeated endovascular treatments, she died on the sixth day of hospitalization. Cerebral venous thrombosis in pregnant women with an antithrombin deficiency can follow a rapid and fatal course. Treatment with unfractionated heparin and antithrombin concentrate may be ineffective in severe cerebral venous thrombosis cases with antithrombin deficiency. Early recognition of antithrombin deficiency and an immediate switch to other anticoagulants may be required. Although the association between cerebral venous thrombosis and the vaccine is uncertain, COVID-19 vaccinations may require careful evaluation for patients with prothrombic factors.
Subject(s)
Antithrombin III Deficiency , COVID-19 , Venous Thrombosis , Humans , Female , Pregnancy , Adult , Pregnant Women , COVID-19/complications , COVID-19 Vaccines/adverse effects , BNT162 Vaccine , Heparin , RNA, Messenger , Antithrombin III Deficiency/complications , Antithrombin III Deficiency/genetics , Antithrombins/therapeutic use , Anticoagulants , Venous Thrombosis/etiology , Vaccination/adverse effectsABSTRACT
BACKGROUND: The best thromboprophylaxis for pregnant women with congenital antithrombin deficiency (CAD) is controversial. OBJECTIVE: To clarify the effectiveness of a protocol for venous thromboembolism (VTE) prevention in pregnant women with CAD. METHODS: Women at high risk of VTE were administered antithrombin concentrate and heparin after conception, whereas those at low risk of VTE were administered heparin alone until delivery. All women received antithrombin concentrate at delivery except for one who was diagnosed with CAD. RESULTS: Ten women had CAD, including one in the high-risk group and nine in the low-risk group. No women had VTE at delivery as per the protocol for VTE prevention. Almost all women had increased antithrombin activity before delivery followed by maintenance at ≥ 70% due to antithrombin concentrate administration. VTE prophylaxis during and after delivery was successful in all women with CAD. However, one woman in the low-risk group did not receive heparin and developed VTE induced by severe hyperemesis at 9 gestational weeks, before the diagnosis of CAD. Women in the high-risk group received antithrombin concentrate after delivery but had increased D-dimer levels at postpartum. CONCLUSIONS: Our protocol to prevent VTE in pregnant women with CAD is safe and effective.
Subject(s)
Antithrombin III Deficiency , Venous Thromboembolism , Anticoagulants/therapeutic use , Antithrombin III , Antithrombin III Deficiency/complications , Antithrombin III Deficiency/drug therapy , Antithrombins/therapeutic use , Female , Heparin/therapeutic use , Humans , Pregnancy , Pregnant Women , Retrospective Studies , Risk Factors , Venous Thromboembolism/etiology , Venous Thromboembolism/prevention & controlABSTRACT
SETTING: In the article, we remember the role of antithrombin (AT) in hemostasis, escalation of AT-potential with heparin and difficulties with monitoring the effectiveness of LMWH therapy (low molecular weight heparin) in patients with AT deficiency. We pay most of our attention to hereditary AT deficiency and its thromboembolic risk in pregnancy. METHODS: In the introduction, the principle of AT function, its two main domains and the regulation of synthesis are cleared. We describe the causal mutations of hereditary AT deficiency in SERPINC1 gen and the relation to a thromboembolic risk. The general recommendations for patients with hereditary AT deficiency and pregnant women are mentioned. As the risk of thromboembolic disease is escalated in pregnancy, the LMWH should always be considered. There has been frequently observed that patients with AT deficiency do not elevate anti-Xa-levels when standard prophylactic LMWH doses are used. This fact well illustrates that heparin without AT may not inhibit the active coagulant factors efficiently enough. Therefore, if a high thromboembolic risk in the patient's anamnesis is present, the LMWH dosing should be escalated. In individual cases, concomitant administration of an antithrombin concentrate to the heparin treatment is recommended at the time of delivery or in the case of deep venous thrombosis. In this article, three cases of unusual pregnancy in patients with different types of AT deficiency are reported. The case reports are summarized from the Department of Hematology at Hospital Kolín, the Centre of Hemostasis and Thrombosis at Institute of Hematology and Blood Transfusion in Prague and from cooperating obstetrical departments in the Czech Republic. RESULTS: We demonstrated the threat of hereditary AT deficiency in three case reports. In one case, the estimated risk of thromboembolism type I of AT-deficiency (quantitative) was in a good correlation with real peripartal complications. In the next two cases with different types of AT deficiency, we showed surprising courses of complicated pregnancies. CONCLUSION: As it has been shown, it is not safe to estimate the risk of thromboembolism on the base of causal mutation for AT deficiency. For present clinical practice, we should still remember AT deficiency as a potentially very dangerous thromboembolic disorder for mother and fetus; thus, excellent cooperation of an obstetrician and a hematologist is necessary.
Subject(s)
Antithrombin III Deficiency , Antithrombin III Deficiency/complications , Antithrombin III Deficiency/genetics , Czech Republic , Female , Fetus , Heparin, Low-Molecular-Weight/therapeutic use , Humans , Mothers , PregnancySubject(s)
COVID-19/blood , Thrombophilia/blood , Thrombosis/blood , Adult , Aged , Antithrombin III/genetics , Antithrombin III Deficiency/blood , Antithrombin III Deficiency/complications , Antithrombin III Deficiency/genetics , COVID-19/complications , COVID-19/physiopathology , Cohort Studies , Factor V Deficiency/blood , Factor V Deficiency/complications , Factor V Deficiency/genetics , Female , Fibrin Fibrinogen Degradation Products , Humans , Hypoprothrombinemias/blood , Hypoprothrombinemias/complications , Hypoprothrombinemias/genetics , Intensive Care Units/statistics & numerical data , Logistic Models , Male , Middle Aged , Mortality , Pilot Projects , Protein C/genetics , Protein C Deficiency/blood , Protein C Deficiency/complications , Protein C Deficiency/genetics , Protein S/genetics , Protein S Deficiency/blood , Protein S Deficiency/complications , Protein S Deficiency/genetics , Respiratory Distress Syndrome/blood , Respiratory Distress Syndrome/physiopathology , SARS-CoV-2 , Severity of Illness Index , Thrombophilia/complications , Thrombophilia/genetics , Thrombophilia/physiopathology , Thrombosis/physiopathologySubject(s)
Antithrombin III Deficiency/genetics , Antithrombin III/genetics , Genetic Variation/genetics , Sinus Thrombosis, Intracranial/genetics , Antithrombin III Deficiency/complications , Antithrombin III Deficiency/diagnostic imaging , Child , Humans , Male , Pedigree , Sinus Thrombosis, Intracranial/complications , Sinus Thrombosis, Intracranial/diagnostic imagingSubject(s)
Antithrombin III Deficiency/drug therapy , Factor Xa Inhibitors/therapeutic use , Venous Thromboembolism/drug therapy , Antithrombin III Deficiency/complications , Factor Xa Inhibitors/adverse effects , Hemorrhage/chemically induced , Humans , Treatment Outcome , Venous Thromboembolism/etiologyABSTRACT
: The incidence of antithrombin III (AT III) deficiency is very rare. The most common complication of AT III deficiency is deep venous thrombosis, which causes a low incidence of intracranial sinus thrombosis. We presented a 31-year-old Chinese woman patient who had a family history of AT III deficiency admitted to our hospital. She had a history of pulmonary embolism. She took rivaroxaban for a long time to prevent thrombosis. After giving birth, she stopped taking the medication for half a year and suffered from drug withdrawal symptoms. Four months after drug withdrawal, she suddenly fell into a coma. After diagnosis, it was found to be caused by a subarachnoid hemorrhage. Finally, she was diagnosed with sagittal and transverse sinus thrombosis. After treatment with mechanical thrombectomy, she fully recovered. In sum, we concluded that mechanical thrombectomy was efficient for AT III deficiency and treating thrombosis.
Subject(s)
Antithrombin III Deficiency/complications , Mechanical Thrombolysis , Sinus Thrombosis, Intracranial/etiology , Sinus Thrombosis, Intracranial/therapy , Adult , Antithrombin III Deficiency/pathology , China/epidemiology , Factor Xa Inhibitors/therapeutic use , Female , Humans , Rivaroxaban/therapeutic use , Sinus Thrombosis, Intracranial/pathologyABSTRACT
The frequency of severe antithrombin deficiency (SAD) was examined in the hematopoietic disorder-, infectious-, and basic-types of the disseminated intravascular coagulation (DIC). A posthoc analysis of 3008 DIC patients (infectious-type, 1794; hematological disorder-type, 813; and basic-type, 401) from post-marketing surveillance data of thrombomodulin alfa was performed. The clinical features of patients and outcomes were compared between patients with and without SAD, using an antithrombin cutoff value of 50%. Patients with SAD accounted for 40.4% of infectious-type DIC, 8.0% of hematopoietic disorder-type DIC, and 26.7% of basic-type DIC. There was no significant difference in thrombin-antithrombin complex levels between patients with and without SAD. The decreased fibrinogen level and differences in clinical features were significantly greater but the increases in fibrinolytic markers were significantly lower in patients with SAD than in those without. The 28-day survival rate was significantly lower in patients with SAD than in those without. Severe antithrombin deficiency was observed in all types of DIC, including hematopoietic disorders. Both hypofibrinolysis and hypercoagulability in patients with SAD may cause multiple organ failure and poor outcomes.
Subject(s)
Antithrombin III Deficiency/complications , Disseminated Intravascular Coagulation/etiology , Fibrinolysis/genetics , Disseminated Intravascular Coagulation/pathology , Female , Humans , Male , Middle AgedABSTRACT
BACKGROUND: Antithrombin (AT) is the primary physiological anticoagulant of normal hemostasis. Hereditary AT deficiency, an autosomal dominant thrombotic disease caused by mutations in the AT gene (SERPINC1), is associated with venous thromboembolism. OBJECTIVE: We investigated the phenotypes, genotypes, and pathogenesis of hereditary AT deficiency in a 12-year-old boy (proband) who developed a pulmonary embolism and a subsequent deep vein thrombosis. METHODS: The AT activity and AT antigen level of the proband and his family members were measured. Mutation sites in all seven exons of SERPINC1 were identified. Analysis of conserved regions around codon 462 of the SERPINC1 gene and functional predictions were performed using bioinformatics tools. RESULTS: The proband, his father, and his paternal grandmother demonstrated reduced AT activity and antigen levels consistent with Type I AT deficiency. A novel heterozygous missense mutation, c.1385G>A (Cys462Tyr) was identified in all three symptomatic family members. This missense mutation causes disruption of the 279Cys-462Cys disulfide bond and leads to type â hereditary AT deficiency. CONCLUSION: A SERPINC1 missense mutation (Cys462Tyr) causing damage to the 279Cys-462Cys disulfide bond of the AT protein appears to be the cause of Type I AT deficiency in this family. These findings indicate one pathological mechanism associated with hereditary AT deficiency.