[Pedigree Analysis and Molecular Mechanism Study of Hereditary Glanzmann Thrombasthenia Caused by Compound Heterozygous Mutation of the ITGA2B Gene].

Objective: The phenotype and genotype of a pedigree with Glanzmann thrombasthenia caused by compound heterozygous mutation in the ITGA2B gene and its molecular pathogenesis were explored. Methods: The platelet aggregation rate of the proband and his family was detected by using a platelet aggregation test with adenosine diphosphate, collagen, epinephrine, arachidonic acid, and ristocetin. The expression levels of CD41 (αⅡb), CD61 (ß3), and CD42b (GPⅠb) on the platelet surface was detected by flow cytometry. Gene sequencing technology was used for the genetic identification of the family. RT-PCR was used in the detection of mRNA splicing, and qRT-PCR was used in detecting the relative mRNA level of the ITGA2B gene. Bioinformatics analysis was used to evaluate the pathogenicity of mutation sites and their effects on protein structure and function. The expressions of total αⅡb and ß3 in platelets were analyzed by Western blot. Results: Except ristocetin, the other four inducers could not induce platelet aggregation in the proband. Flow cytometry showed that the expression levels of αⅡb and ß3 were only 0.25% and 9.76%, respectively, on the platelet surface of the proband, whereas GPⅠb expression was relatively normal. The expression levels of glycoproteins in the other family members were almost normal. c.480C>G and c.2929C>T mutations were detected in the proband through gene sequencing. The c.480C>G mutation was inherited from his mother, and the c.2929C>T mutation was inherited from his father. The RT-PCR and sequencing results showed that the c.480C>G mutation caused mRNA splicing in the proband and his mother, resulting in the deletion of 99 bases in c.476G-574A (p.S160-S192). qRT-PCR showed that the c.2929C>T variant reduced the mRNA level of the ITGA2B gene in the proband and his father. Bioinformatics analysis suggested that the c.480C>G mutation might form a binding sequence with hnRNP A1 protein and generate the 5'SS splice site. The three-dimensional structural model of the αⅡb subunit showed that the ß-propeller domain of the p.S160-S192 deletion lost two ß-strands and one α-helix in blade 2. The c.2929C>T nonsense mutation caused premature translation termination and produced a truncated protein with the deletion of p.R977-E1039, including the cytoplasmic domain, transmembrane domain, and a ß chain of the extracellular Calf-2 domain. The total αⅡb expression of the proband was absent, and the relative expression of ß3 was 11.36% of the normal level. Conclusion: The compound heterozygous mutation c.480C>G in exon 4 and c.2929C>T in exon 28 of the ITGA2B gene probably underlies Glanzmann thrombasthenia in this pedigree.

Should HLA and HPA-matched platelet transfusions for patients with Glanzmann Thrombasthenia or Bernard-Soulier syndrome be standardized care? A Dutch survey and recommendations.

BACKGROUND: Glanzmann thrombasthenia (GT) and Bernard-Soulier syndrome (BSS) patients require frequent platelet transfusions and hence have an increased risk for alloimmunization against donor Human Leukocyte Antigens (HLA) when no HLA-matching is performed. Knowing that Human Platelet Antigens (HPA) are located on the platelet glycoproteins that can be absent in these patients, preventive HPA-matching may also be considered. Uniform recommendations on this topic lack in transfusion guidelines making standard practice unclear, therefore, we aimed to provide a framework for matched platelet transfusions. STUDY DESIGN AND METHODS: We conducted a targeted literature search and a national survey of Dutch (pediatric) hematologists from July to September 2021. RESULTS: We found 20 articles describing platelet transfusion policies in 483 GT-patients and 29 BSS-patients, both adults and children. Twenty surveys were returned for full analysis. All responders treated patients with platelet disorders, including GT (n = 36 reported) and BSS (n = 29 reported). Of respondents, 75% estimated the risk of antibody formation as "likely" for HLA and 65% for HPA. Formation of HLA antibodies was reported in 5 GT and in 5 BSS-patients, including one child. Fifteen respondents gave preventive HLA-matched platelets in elective setting (75%). Three respondents additionally matched for HPA in GT-patients (15%). Main argument for matched platelet transfusions was preventing alloimmunization to safeguard the effectivity of 'random' donor-platelets in acute settings. CONCLUSION: Elective HLA-matching for GT and BSS-patients is already conducted by most Dutch (pediatric) hematologists. HPA-matching is mainly applied when HPA-antibodies are formed. Based on the current literature and the survey, recommendations are proposed.

A novel ITGA2B double cytosine frameshift variant (c.1986_1987insCC) leads to Glanzmann's thrombasthenia in a cat.

BACKGROUND: Glanzmann's thrombasthenia (GT) is a congenital platelet disorder affecting approximately 1:1 000 000 people globally and characterized by impaired platelet aggregation and clot retraction. Autosomal recessive, loss-of-function, variants in ITGA2B or ITGB3 of the αIIbß3 receptor cause the disease in humans. A cat affected by Glanzmann's and macrothrombocytopenia was presented to the UC Davis VMTH. HYPOTHESIS/OBJECTIVES: Severe thrombopathia in this cat has an underlying genetic etiology. ANIMALS: A single affected patient, 2 age-matched clinically healthy controls, and a geriatric population (n = 20) of normal cats. METHODS: Physical examination and clinical pathology tests were performed on the patient. Flow cytometry and platelet aggregometry analyses for patient phenotyping were performed. Patient and validation cohort gDNA samples were extracted for Sanger sequencing of a previously identified ITGA2B (c.1986delC) variant. Reverse transcriptase PCR was performed on patient and healthy control PRP samples to verify ITGA2B variant consequence. RESULTS: A novel c.1986_1987insCC autosomal recessive variant in ITGA2B was identified. This variant was absent in a population of 194 unrelated cats spanning 44 different breeds. Complete loss of ITGA2B transcript and protein expression was verified by RT-PCR and flow cytometry, explaining the underlying etiology of GT, and likely macrothrombocytopenia, in this cat. CONCLUSIONS AND CLINICAL IMPORTANCE: This study emphasizes the role of precision medicine in cardiovascular disease of cats and identified yet another variant that may be of utility for screening in the feline population. This study provides a small-volume, standardized, successful protocol for adequate platelet RNA isolation and subsequent molecular assessment of gene expression in cats.

Immune gene polymorphisms associated with poor response to platelet transfusion and recombinant factor VII administration in Glanzmann thrombasthenia.

INTRODUCTION: Poor response to platelet and recombinant factor VII administration is a major problem in patients with Glanzmann Thrombasthenia (GT). The risk factors associated with poor response to treatment in these patients are unknown. Some genetic variations of cytokines may contribute to therapy resistance. AIMS: We evaluated, for the first time, whether genetic polymorphisms on cytokine genes are related to poor treatment response in GT patients. METHODS: We enrolled 30 patients with GT (15 resistant and 15 non-resistant) and 100 healthy controls. Gene polymorphisms of IL-10 and TNF-α were analysed using TaqMan Realtime PCR, and IL-1, IL-1R1 and IL-1RN were investigated with the RFLP method. In-silico analyses were performed to predict the potential impact of these polymorphisms. RESULTS: In the resistant group, all patients had a variant of the IL-10 gene at the -1082 position (rs1800896), with a GG genotype that was significantly more frequent than the non-resistant group. Analysis between healthy controls and GT patients revealed a probable correlation between rs3783550, rs3783553, rs3917356 and rs2234463 and GT. The In-silico study indicated that TNF-α rs1800629 and IL-10 rs1800896 polymorphisms result in different allelic expressions which may contribute to poor response to therapy. CONCLUSIONS: These findings suggest that polymorphisms in the IL-10 and IL-1 receptor antagonist genes may play a role in poor therapy response in GT patients. In addition, some polymorphisms in IL-1α, IL1-ß, IL-1R1 and IL-R antagonists might be involved in the GT progression.

Frequency, clinical, and laboratory findings of platelet secretion disorders in patients referred to the specialized coagulation laboratory of the Iranian Blood Transfusion Organization.

OBJECTIVES: Platelet secretion disorders (PSDs) are a subgroup of platelet function disorders (PFDs) caused by defects in the content or release of platelet granules. These patients have a variable degree of mucocutaneous bleeding tendency. The diagnostic facilities of PSDs are imitated in Iran, even in specialized coagulation laboratories. The present study aims to estimate the frequency of PSDs among patients referred to the Iranian Blood Transfusion Organization (IBTO). METHODS: The research population includes all patients referred to the specialized coagulation laboratory of IBTO and requested platelet function and von Willebrand testing by their physicians. They were recruited between May 2022 and October 2022 if they were not diagnosed as having procoagulant defects, von Willebrand disease (VWD), Glanzmann thrombasthenia (GT), Bernard-Soulier syndrome (BSS), and platelet count <100 × 10 9 (except in the syndromic forms). Patients with a defect in response to at least two agonists in Light transmission aggregometry (LTA), one agonist in the ATP-secretion study, and/or impairment in the expression of CD62P are considered PSDs. RESULTS: Among 121 cases referred to our center over 6 months, 40 patients fulfilled the inclusion and exclusion criteria. Ten patients were diagnosed with PSDs. Six were classified as δ-platelet secretion disorders (δ-PSD), two α-platelet secretion disorders (α-PSD), and two αδ-platelet secretion disorders (αδ-PSD). CONCLUSIONS: The prevalence of PSDs in our population study was 25% (10/40), which seems highly prevalent. Therefore, expanding laboratory approaches to platelet function defects is necessary as a routine in our country.

Bleeding disorders in Saudi Arabia, causes and prevalence: a review.

As bleeding disorders are a worldwide health concern, Saudi Arabia is experiencing a notable prevalence of such disorders. Studying the frequency and cause of hemostatic disorders is the key to successful clinical interventions and instigating effective public policies that limit the spread of such disorders. The current review aims to highlight the major findings of the body of literature that has investigated the causes, prevalence, and major challenges associated with bleeding disorders in the country. The current review summarizes the major findings of different studies that have been conducted in Saudi Arabia regarding different bleeding disorders. Multiple causes and symptoms of bleeding disorders have been reported by different studies. Some studies investigated the genetic aspect of bleeding disorders and revealed specific mutations in coagulation factor genes influencing the symptoms of different bleeding disorders. Moreover, rare bleeding disorders such as Glanzmann thrombasthenia and Henoch-Schönlein purpura, have been reported in different regions of Saudi Arabia. Combining clinical presentations, genetic factors, and epidemiological data, the current review of the literature provides a comprehensive insight into bleeding disorders in the kingdom. This will help in advancing the diagnostic capabilities and genetic counseling enhancing management strategies and therapeutic interventions benefiting bleeding disorder patients and the kingdom.

Double jeopardy, glomangiopericytoma and Glanzmann thrombasthenia resulting in recurrent epistaxis: a case report.

Glanzmann thrombasthenia is a rare bleeding disorder induced by inherited defects of the platelet membrane αIIbß3 glycoprotein. Glomangiopericytoma, on the other hand, is a very rare sinonasal tumor demonstrating a perivascular myoid phenotype. We herein report the first described case in the literature of Glanzmann thrombasthenia and glomangiopericytoma. The patient is a 40-year-old man diagnosed with type 1 Glanzmann thrombasthenia who presented with repetitive and profuse posterior epistaxis initially managed with platelet transfusions and recombinant activated factor VII (rFVIIa). Due to the unresolved epistaxis, nasal endoscopy was performed revealing a vascularized tumor. Subsequently, a sphenopalatine artery embolization followed by a surgical excision of the tumor was performed. The pathology report diagnosis of the tumor was glomangiopericytoma. This case sheds the lights on a very rare cause of epistaxis in a patient with Glanzmann thrombasthenia, with a challenging multidisciplinary management. A local cause of epistaxis should always be considered even in case of a diagnosed bleeding disorder, especially when the bleeding is recurrent.

Utility of the international society on thrombosis and hemostasis-bleeding assessment tool in the diagnosis of patients who suspected of platelet function disorders.

The ISTH-BAT is a structured bleeding assessment tool to record and help diagnose patients with possible bleeding disorders. However, a few studies evaluated the utility of ISTH-BAT in diagnosing patients with platelet function defects (PFDs). In this study, we evaluated the diagnostic utility of ISTH-BAT in predicting PFDs among patients suspected of PFDs. Forty patients suspected of PFDs and 21 normal healthy controls were evaluated by the ISTH-BAT scoring system, light transmission aggregometry (LTA), ATP-releasing assays (lumi-aggregometry), and expression of CD62P for diagnosis of PFDs. Among 40 patients suspected of PFDs, 10 were diagnosed as PFDs using lumiaggregometry and CD62P. The ISTH-BAT score in patients suspected of PFDs [(6, interquartile range (IQR) 1-8] and patients with PFDs was significantly higher than the control group (0; IQR 0-0) ( P  < 0.001). Receiver operating characteristic curves indicate that ISTH-BAT is not able to discriminate patients with PFDs from those without PFDs (areas under the curve of 0.620 (95% confidence interval 0.415-0.825). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the ISTH-BAT in predicting the presence of PFDs, respectively, were 40, 73.3, 33.3, and 78.6% in the cut-off ISTH-BAT at least 4 in adult men, at least 6 in adult women, and at least 3 in children (age < 18). The ISTH-BAT scoring system has good discriminatory power in diagnosing patients with PFDs from healthy controls but is ineffective in differentiating them from those without PFDs.

Targeted long-read sequencing identifies and characterizes structural variants in cases of inherited platelet disorders.

BACKGROUND: Genetic diagnosis of inherited platelet disorders (IPDs) is mainly performed by high-throughput sequencing (HTS). These short-read-based sequencing methods sometimes fail to characterize the genetics of the disease. OBJECTIVES: To evaluate nanopore long-read DNA sequencing for characterization of structural variants (SVs) in patients with IPDs. METHODS: Four patients with a clinical and laboratory diagnosis of Glanzmann thrombasthenia (GT) (P1 and P2) and Hermansky-Pudlak syndrome (HPS) (P3 and P4) in whom HTS missed the underlying molecular cause were included. DNA was analyzed by both standard HTS and nanopore sequencing on a MinION device (Oxford Nanopore Technologies) after enrichment of DNA spanning regions covering GT and HPS genes. RESULTS: In patients with GT, HTS identified only 1 heterozygous ITGB3 splice variant c.2301+1G>C in P2. In patients with HPS, a homozygous deletion in HPS5 was suspected in P3, and 2 heterozygous HPS3 variants, c.2464C>T (p.Arg822∗) and a deletion affecting 2 exons, were reported in P4. Nanopore sequencing revealed a complex SV affecting exons 2 to 6 in ITGB3 (deletion-inversion-duplication) in homozygosity in P1 and compound heterozygosity with the splice variant in P2. In the 2 patients with HPS, nanopore defined the length of the SVs, which were characterized at nucleotide resolution. This allowed the identification of repetitive Alu elements at the breakpoints and the design of specific polymerase chain reactions for family screening. CONCLUSION: The nanopore technology overcomes the limitations of standard short-read sequencing techniques in SV characterization. Using nanopore, we characterized novel defects in ITGB3, HPS5, and HPS3, highlighting the utility of long-read sequencing as an additional diagnostic tool in IPDs.

Multidisciplinary management of a pregnancy complicated by Glanzmann thrombasthenia: A case report.

BACKGROUND: Glanzmann thrombasthenia (GT) is a rare, autosomal recessive disorder of platelet glycoprotein IIb-IIIa receptors. Pregnant patients with GT are at increased risk of maternal and fetal bleeding. There is a paucity of literature on the peripartum management of patients. CASE DESCRIPTION: We present the antepartum through the postpartum course of a patient with GT who was managed by a multidisciplinary approach that included communication across maternal-fetal medicine, hematology, transfusion medicine, and anesthesiology services. In addition to routine prepartum obstetric imaging and hematologic laboratory studies, we proactively monitored the patient for anti-platelet antibodies every 4-6 weeks to gauge the risk for neonatal alloimmune thrombocytopenia. Furthermore, we prioritized uterotonics, tranexamic acid, and transfusion of HLA-matched platelets to manage bleeding for mother and fetus intrapartum through the postpartum periods. CONCLUSION: To date, there are limited guidelines for managing bleeding or preventing alloimmunization during pregnancy in patients with GT. Here, we present a complex case with aggressive management of bleeding prophylactically for the mother while serially monitoring both mother and fetus for peripartum bleeding risks and events. Moreover, future studies warrant continued evaluation of these approaches to mitigate increased bleeding risks in subsequent pregnancies.

Glanzmann's thrombasthenia associated with gastrointestinal angiodysplasias successfully treated with bevacizumab.

Glanzmann's Thrombasthenia (GT) is a rare hemorrhagic condition caused by a platelet surface receptor disorder of the glycoprotein (GP) IIb/IIIa. Symptoms of GT are various forms of hemorrhages, such as purpura, epistaxis and menorrhagia. Gastrointestinal bleeding (GIB) is a rare expression of the condition and may occur due to traumas in the GI tract or as a consequence of gastrointestinal angiodysplasia (GIADs). In this case report, we present a middle-aged woman with recurrent GIB consequent to GIADs with persistent melena and iron deficiency anemia. After several unsuccessful therapeutic interventions, the patient was studied by the hereditary hemorrhagic telangiectasia's (HHT - Osler-Weber-Rendu disease) unit, where she received bevacizumab, showing a complete improvement in symptoms as well as a reduction in her GIADs. This case shows that bevacizumab could be a possible line of treatment for patients with coagulation disorders with GIADs.

Effect of c.1431C > T mutation, a causative mutation of Glanzmann's thrombasthenia, on ITGB3 splicing, gene and protein expression.

BACKGROUND/AIM: Recently, it was reported that the non-synonymous c.1431C > T (p. G477=) mutation of the integrin subunit ß3 (ITGB3) gene is the cause of Glanzmann's thrombasthenia (GT). However, the functional consequences of this mutation on the ITGB3 gene and protein expression remain to be elucidated. Therefore, this study was conducted to cover this scientific shortage. METHODS: Peripheral blood samples were collected from Chinese family members (parents and proband and his sister), and DNA was extracted and sequenced using whole-exome and Sanger sequencing. The effect of c.1431C > T mutation on the splicing of mRNA was verified by the in vitro minigene assay and the three variants that resulted from the mutation were cloned into a phage vector and pEGFP-C1 vector, and ITGB3 gene and protein expression was detected in the transfected 293 T cells using qPCR and Western blotting. RESULTS: Minigene splicing assay showed that c.1431C > T mutation causes three kinds of alternative splicing; (1) a 95 bp deletion in the middle of exon10, (2) a 155 bp deletion (95 bp deletion in the middle of exon10 plus a 60 bp deletion in the right side of exon10), and (3) a 261 bp deletion in the right side of exon10. The in vitro expression assay showed that the c.1431C > T variant did not affect the ITGB3 mRNA levels, but directly led to protein truncation and declined expression. CONCLUSION: Due to its significant impact on protein expression, c.1431C > T mutation in ITGB3 could be considered a pathogenic variant of GT. This could enrich the ITGB3 mutation spectrum and provide a base for the genetic diagnosis of GT.

A lethal case of massive hemorrhage after percutaneous liver biopsy in a patient with thrombasthenia.

Percutaneous needle liver biopsy is an important procedure in the diagnosis of and assessment of the severity of liver diseases. Although liver biopsy is considered to be a relatively safe procedure, there are occasional cases of death due to massive bleeding after liver biopsy. Thrombasthenia is a disease in which bleeding occurs in the mucosa and skin due to platelet dysfunction. A 60-year-old female was admitted for a liver biopsy for further investigation after an abnormal liver function test. She was diagnosed with thrombasthenia and was being treated with oral tranexamic acid and carbazochrome. Blood tests showed little decrease of platelet count and no abnormalities of blood coagulability. Approximately ten hours after the liver biopsy, the patient complained of nausea and lightheadedness, followed by decreased blood pressure and decreased consciousness. An emergent abdominal CT scan showed a large amount of blood in the abdominal cavity. The patient died despite multidisciplinary treatment, and a forensic autopsy was performed. At internal examination, approximately 2,620 mL of dark red blood was accumulated in the abdominal cavity. A puncture wound led 1.8 cm into the liver from the surface of the liver, and no major vascular damage was observed. The cause of death was considered to be blood loss due to bleeding from the puncture wound. Even if the platelet count is normal, such as in a case of thrombasthenia, the risk of bleeding should not be underestimated. Careful attention should be paid when performing liver biopsy in a patient with risk factors.

SINE-VNTR-Alu retrotransposon insertion as a novel mutational event underlying Glanzmann thrombasthenia.

BACKGROUND: Glanzmann thrombasthenia (GT) is an autosomal recessive platelet aggregation disorder caused by mutations in ITGA2B or ITGB3. OBJECTIVES: We aimed to assess the phenotype and investigate the genetic etiology of a GT pedigree. METHODS: A patient with bleeding manifestations and mild mental retardation was enrolled. Complete blood count, coagulation, and platelet aggregation tests were performed. Causal mutations were identified via whole exome and genome sequencing and subsequently confirmed through polymerase chain reaction and Sanger sequencing. The transcription of ITGB3 was characterized using RNA sequencing and reverse transcription polymerase chain reaction. The αⅡb and ß3 biosynthesis was investigated via whole blood flow cytometry and in vitro studies. RESULTS: GT was diagnosed in a patient with defective platelet aggregation. Novel compound heterozygous ITGB3 variants were identified, with a maternal nonsense mutation (c.2222G>A, p.Trp741∗) and a paternal SINE-VNTR-Alu (SVA) retrotransposon insertion. The 5' truncated SVA element was inserted in a sense orientation in intron 11 of ITGB3, resulting in aberrant splicing of ITGB3 and significantly reducing ß3 protein content. Meanwhile, both the expression and transportation of ß3 were damaged by the ITGB3 c.2222G>A. Almost no αⅡb and ß3 expressions were detected on the patient's platelets surface. CONCLUSION: Novel compound heterozygous ITGB3 mutations were identified in the GT pedigree, resulting in defects of αⅡbß3 biosynthesis. This is the first report of SVA retrotransposon insertion in the genetic pathogenesis of GT. Our study highlights the importance of combining multiple high-throughput sequencing technologies for the molecular diagnosis of genetic disorders.

Emergency management of patients with Glanzmann thrombasthenia: consensus recommendations from the French reference center for inherited platelet disorders.

Glanzmann thrombasthenia (GT) is a genetic bleeding disorder characterised by severely reduced/absent platelet aggregation in response to multiple physiological agonists. The severity of bleeding in GT varies markedly, as does the emergency situations and complications encountered in patients. A number of emergency situations may occur in the context of GT, including spontaneous or provoked bleeding, such as surgery or childbirth. While general management principles apply in each of these settings, specific considerations are essential for the management of GT to avoid escalating minor bleeding events. These recommendations have been developed from a literature review and consensus from experts of the French Network for Inherited Platelet Disorders, the French Society of Emergency Medicine, representatives of patients' associations, and Orphanet to aid decision making and optimise clinical care by non-GT expert health professionals who encounter emergency situations in patients with GT.

Molecular dynamics simulations corroborate recombinant expression studies carried out on three αIIb ß-propeller mutations reported in Indian Glanzmann thrombasthenia patients.

Mutations in the αIIb ß-propeller domain have long been known to disrupt heterodimerization and intracellular trafficking of αIIbß3 complexes leading to diminished surface expression and/or function, resulting in Glanzmann thrombasthenia. Our previous study on three ß-propeller mutations, namely G128S, S287L, and G357S, showed variable defects in protein transport correlated with the patient's clinical phenotypes. Pulse-chase experiments revealed differences in αIIbß3 complex maturation among the three mutations. Hence, the current study aims to correlate conformational changes caused by each one of them. Evolutionary conservation analysis, stability analysis, and molecular dynamics simulations of the three mutant structures were carried out. Stability analysis revealed that, while G128S and G357S mutations destabilized the ß-propeller structure, S287L retained the stability. Wild-type and mutant ß-propeller structures, when subjected to molecular dynamics simulations, confirmed that G128S and G357S were both destabilizing in nature when compared with the wild-type and S287L based on several parameters studied, like RMSD, RMSF, Rg, FEL, PCA, secondary structure, and hydrogen bonds. In our previous study, we demonstrated that mutant S287L αIIbß3 complexes were more stable than the wild-type αIIbß3 complexes, as evidenced in pulse-chase experiments. These findings corroborate variable intracellular fates of mutant αIIbß3 complexes as a result of these ß-propeller mutations.

Monozygotic twin cases of endometriosis with Glanzmann thrombasthenia: a case report and review of literature.

BACKGROUND: Glanzmann thrombasthenia (GT) is a rare bleeding disorder with a high prevalence in communities where consanguineous marriages are mainstream. Endometriosis is a chronic inflammatory disease, and its risk increases in women with menstrual periods of longer than six days. The phenotypic expression of endometriosis is determined by the frequency and rate of the menstrual flow, as well as genetic and environmental factors. RESULT AND CASE PRESENTATION: 14-year-old monozygotic twin sisters with GT who developed ovarian endometriosis were referred to Hazrat Rasoul Hospital due to severe dysmenorrhea. In ultrasonic examination, endometrioma cysts were reported in both patients. They both went under endometrioma cystectomy, and the bleeding was managed using antifibrinolytic drugs, followed by recombinant activated coagulation factor VII. Both were discharged after 3 days. In the ultrasound examination performed one year after the surgery, ovaries were normal in the first twin, while the second twin had a 28 × 30 hemorrhagic cyst in the left ovary. DISCUSSION AND CONCLUSION: Menstrual bleeding and genetic factors are two theories that could be related to GT and endometriosis association, and GT could be considered a risk factor for endometriosis.