Clonal PIGA mosaicism and dynamics in paroxysmal nocturnal hemoglobinuria.
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ABSTRACT:
SUBMITTER: Clemente MJ
PROVIDER: S-EPMC8694093 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundParoxysmal nocturnal hemoglobinuria (PNH) is an acquired pluripotent hematopoietic stem cell disorder associated with an increase in the number of glycosyl-phosphatidyl inositol (GPI)-deficient blood cells. We investigated PNH clonal proliferation in the three cell lineages-granulocytes, T lymphocytes, and red blood cells (RBCs)-by analyzing PIGA gene mutations and T-cell receptor (TCR) clonality.MethodsFlow cytometry was used on peripheral blood samples from 24 PNH patients to measure the GPI-anchored protein (GPI-AP) deficient fraction in each blood cell lineage. PIGA gene mutations were analyzed in granulocytes and T lymphocytes by Sanger sequencing. A TCR clonality assay was performed in isolated GPI-AP deficient T lymphocytes.ResultsThe GPI-AP deficient fraction among the three lineages was the highest in granulocytes, followed by RBCs and T lymphocytes. PIGA mutations were detected in both granulocytes and T lymphocytes of 19 patients (79.2%), with a higher mutation burden in granulocytes. The GPI-AP deficient fractions of granulocytes and T lymphocytes correlated moderately (rs=0.519, P=0.049) and strongly (rs=0.696, P=0.006) with PIGA mutation burden, respectively. PIGA mutations were more frequently observed in patients with clonal rearrangements in TCR genes (P=0.015). The PIGA mutation burden of T lymphocytes was higher in patients with clonal TCRB rearrangement.ConclusionsPIGA mutations were present in approximately 80% of PNH patients. PNH clone size varies according to blood cell lineage, and clonal cells may obtain proliferation potential or gain a survival advantage over normal cells.
| S-EPMC6502953 | biostudies-literature
Project description:Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal blood disorder characterized by hemolysis and a high risk of thrombosis, that is due to a deficiency in several cell surface proteins that prevent complement activation. Its origin has been traced to a somatic mutation in the PIG-A gene within hematopoietic stem cells (HSC). However, to date the question of how this mutant clone expands in size to contribute significantly to hematopoiesis remains under debate. One hypothesis posits the existence of a selective advantage of PIG-A mutated cells due to an immune mediated attack on normal HSC, but the evidence supporting this hypothesis is inconclusive. An alternative (and simpler) explanation attributes clonal expansion to neutral drift, in which case selection neither favours nor inhibits expansion of PIG-A mutated HSC. Here we examine the implications of the neutral drift model by numerically evolving a Markov chain for the probabilities of all possible outcomes, and investigate the possible occurrence and evolution, within this framework, of multiple independently arising clones within the HSC pool. Predictions of the model agree well with the known incidence of the disease and average age at diagnosis. Notwithstanding the slight difference in clonal expansion rates between our results and those reported in the literature, our model results lead to a relative stability of clone size when averaging multiple cases, in accord with what has been observed in human trials. The probability of a patient harbouring a second clone in the HSC pool was found to be extremely low ([Formula: see text]). Thus our results suggest that in clinical cases of PNH where two independent clones of mutant cells are observed, only one of those is likely to have originated in the HSC pool.
| S-EPMC6023248 | biostudies-literature
Project description:Paroxysmal nocturnal hemoglobinuria (PNH) is a rare bone marrow failure disorder that manifests with hemolytic anemia, thrombosis, and peripheral blood cytopenias. The absence of two glycosylphosphatidylinositol (GPI)-anchored proteins, CD55 and CD59, leads to uncontrolled complement activation that accounts for hemolysis and other PNH manifestations. GPI anchor protein deficiency is almost always due to somatic mutations in phosphatidylinositol glycan class A (PIGA), a gene involved in the first step of GPI anchor biosynthesis; however, alternative mutations that cause PNH have recently been discovered. In addition, hypomorphic germ-line PIGA mutations that do not cause PNH have been shown to be responsible for a condition known as multiple congenital anomalies-hypotonia-seizures syndrome 2. Eculizumab, a first-in-class monoclonal antibody that inhibits terminal complement, is the treatment of choice for patients with severe manifestations of PNH. Bone marrow transplantation remains the only cure for PNH but should be reserved for patients with suboptimal response to eculizumab.
| S-EPMC4215311 | biostudies-literature
Project description:Phosphatidylinositol glycan class A (PIGA) is involved in the first step of glycosylphosphatidylinositol (GPI) biosynthesis. Many proteins, including CD55 and CD59, are anchored to the cell by GPI. Loss of CD55 and CD59 on erythrocytes causes complement-mediated lysis in paroxysmal nocturnal hemoglobinuria (PNH), a disease that manifests after clonal expansion of hematopoietic cells with somatic PIGA mutations. Although somatic PIGA mutations have been identified in many PNH patients, it has been proposed that germline mutations are lethal. We report a family with an X-linked lethal disorder involving cleft palate, neonatal seizures, contractures, central nervous system (CNS) structural malformations, and other anomalies. An X chromosome exome next-generation sequencing screen identified a single nonsense PIGA mutation, c.1234C>T, which predicts p.Arg412(?). This variant segregated with disease and carrier status in the family, is similar to mutations known to cause PNH as a result of PIGA dysfunction, and was absent in 409 controls. PIGA-null mutations are thought to be embryonic lethal, suggesting that p.Arg412(?) PIGA has residual function. Transfection of a mutant p.Arg412(?) PIGA construct into PIGA-null cells showed partial restoration of GPI-anchored proteins. The genetic data show that the c.1234C>T (p.Arg412(?)) mutation is present in an affected child, is linked to the affected chromosome in this family, is rare in the population, and results in reduced, but not absent, biosynthesis of GPI anchors. We conclude that c.1234C>T in PIGA results in the lethal X-linked phenotype recognized in the reported family.
| S-EPMC3276655 | biostudies-literature
Project description:Pregnancies in paroxysmal nocturnal hemoglobinuria (PNH) are associated with increased morbidity and mortality. Retrospective studies suggest that outcome has improved with the advent of the complement inhibitor eculizumab. To substantiate this assumption we analyzed the data from patients treated in our department since 2009. All patients were included in the International PNH registry and followed prospectively. We identified 16 pregnancies in 9 patients with classical PNH, and two pregnancies in two patients with aplastic anemia (AA)-PNH. In classical PNH, 13 pregnancies were supported by eculizumab. Breakthrough hemolysis occurred in six pregnancies, necessitating an increase in the biweekly eculizumab dose from 900 mg to 1,200-1,800 mg. Red blood cell transfusions were given in six and platelet transfusions in two pregnancies. A Budd-Chiari syndrome and cholecystitis complicated the course of two pregnancies. Four of 13 pregnancies supported by eculizumab ended in spontaneous abortion or stillbirth, and one was prematurely terminated because of fetal trisomy 21. None of the three pregnancies not supported by eculizumab had a successful outcome. Half the deliveries were preterm. None of the patients died, and, in all but one patient, the post-partum period was uneventful. Both pregnancies in patients with AA-PNH took a favorable course. Our results confirm low maternal mortality and frequent breakthrough hemolysis in pregnant PNH patients receiving eculizumab. Fetal mortality and the rate of preterm delivery were higher than reported previously, possibly related to the use of registry data that are likely to reduce the risk of publication and recall biases.
| S-EPMC7546795 | biostudies-literature
Project description:Clinical and hematological parameters in six cases of paroxysmal nocturnal hemoglobinuria (PNH) are presented. The mean delay in diagnosis after onset of symptoms was 3.7 years. Initial diagnoses considered were: (a) hematuria; (b) iron-deficiency; hemolytic; megaloblastic or refractory anemia and (c) myelodysplastic syndrome. Clinical features included; reddish urine (5/6), unexplained abdominal pain (4/6) and pallor (6/6). Laboratory investigations showed anemia (6/6), leucopenia (3/6), thrombocytopenia (3/6), unconjugated hyperbilirubinemia at some stage (6/6), and bone marrow erythroid hyperplasia (6/6). Complications encountered were (a) gall stones needing cholecystectomy, hemosiderosis and proximal tubular acidosis in 1 case, (b) disseminated tuberculosis in 1 case and (c) abortion with congestive cardiac failure in one. PNH may present with atypical features and tests for hemosiderinuria, sucrose lysis test and HAM's test are required to establish the diagnosis.
| S-EPMC5529684 | biostudies-literature
Project description: Not available
| S-EPMC8672449 | biostudies-literature
Project description:Somatic mutation of PIGA in hematopoietic stem cells causes deficiency of glycosyl phosphatidylinositol-anchored proteins in paroxysmal nocturnal hemoglobinuria (PNH) that underlies the intravascular hemolysis but does not account for expansion of the PNH clone. Immune mechanisms may mediate clonal selection but appear insufficient to account for the clonal dominance necessary for PNH to become clinically apparent. Herein, we report 2 patients with PNH whose PIGA-mutant cells had a concurrent, acquired rearrangement of chromosome 12. In both cases, der(12) had a break within the 3' untranslated region of HMGA2, the architectural transcription factor gene deregulated in many benign mesenchymal tumors, that caused ectopic expression of HMGA2 in the bone marrow. These observations suggest that aberrant HMGA2 expression, in concert with mutant PIGA, accounts for clonal hematopoiesis in these 2 patients and suggest the concept of PNH as a benign tumor of the bone marrow.
| S-EPMC1895453 | biostudies-literature
Project description:Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, life-threatening hematologic stem cell disorder characterized by hemoglobinuria, thrombosis, and tendency for bone marrow failure. The rare incidence of PNH in children, its nonspecific clinical presentation, and occasional absence of hemoglobinuria make the diagnosis challenging. We present a case of a 17-year-old boy who was hospitalized with a history of recurrent abdominal pain, fever, and dark-colored urine. Laboratory tests revealed anemia, thrombocytopenia, and elevated inflammatory markers. Urinalysis was positive for protein and red blood cells, too many to be counted. Complement studies were within normal limits. Abdominal computed tomography showed a segment of the small bowel with wall thickening and signs of possible microperforation. Exploratory laparotomy revealed necrosis of the small bowel, and histological evaluation was suggestive of an autoimmune process with small vessel vasculitis. Bone marrow biopsy showed hypocellular marrow with a decreased number of myeloid cells, normal number of megakaryocytes, and signs of erythroid hyperplasia. Flow cytometry detected deficiency of CD59 leading to the diagnosis of PNH. The patient was treated with eculizumab infusions resulting in significant improvement. This case highlights the need for high clinical suspicion for rare entities such as PNH in patients presenting without hemoglobinuria.
| S-EPMC6590537 | biostudies-literature
Project description:Complement C5 inhibition is the standard of care (SoC) for patients with paroxysmal nocturnal hemoglobinuria (PNH) with significant clinical symptoms. Constant and complete suppression of the terminal complement pathway and the high serum concentration of C5 pose challenges to drug development that result in IV-only treatment options. Crovalimab, a sequential monoclonal antibody recycling technology antibody was engineered for extended self-administered subcutaneous dosing of small volumes in diseases amenable for C5 inhibition. A 3-part open-label adaptive phase 1/2 trial was conducted to assess safety, pharmacokinetics, pharmacodynamics, and exploratory efficacy in healthy volunteers (part 1), as well as in complement blockade-naive (part 2) and C5 inhibitor-treated (part 3) PNH patients. Twenty-nine patients were included in part 2 (n = 10) and part 3 (n = 19). Crovalimab concentrations exceeded the prespecified 100-µg/mL level and resulted in complete and sustained terminal complement pathway inhibition in treatment-naive and C5 inhibitor-pretreated PNH patients. Hemolytic activity and free C5 levels were suppressed below clinically relevant thresholds (liposome assay <10 U/mL and <50 ng/mL, respectively). Safety was consistent with the known profile of C5 inhibition. As expected, formation of drug-target-drug complexes was observed in all 19 patients switching to crovalimab, manifesting as transient mild or moderate vasculitic skin reactions in 2 of 19 participants. Both events resolved under continued treatment with crovalimab. Subcutaneous crovalimab (680 mg; 4 mL), administered once every 4 weeks, provides complete and sustained terminal complement pathway inhibition in patients with PNH, warranting further clinical development (ClinicalTrials.gov identifier, NCT03157635).
| S-EPMC7082616 | biostudies-literature