Satheesh Chonat

Clinical spectrum of pyruvate kinase deficiency: Data from the pyruvate kinase deficiency natural history study

An international, multicenter registry was established to collect retrospective and prospective clinical data on patients with pyruvate kinase (PK) deficiency, the most common glycolytic defect causing congenital nonspherocytic hemolytic anemia. Medical history and laboratory and radiologic data were retrospectively collected at enrollment for 254 patients with molecularly confirmed PK deficiency. Perinatal complications were common, including anemia that required transfusions, hyperbilirubinemia, hydrops, and prematurity. Nearly all newborns were treated with phototherapy (93%), and many were treated with exchange transfusions (46%). Children age 5 years and younger were often transfused until splenectomy. Splenectomy (150 [59%] of 254 patients) was associated with a median increase in hemoglobin of 1.6 g/dL and a decreased transfusion burden in 90% of patients. Predictors of a response to splenectomy included higher presplenectomy hemoglobin (P = .007), lower indirect bilirubin (P = .005), and missense PKLR mutations (P = .0017). Postsplenectomy thrombosis was reported in 11% of patients. The most frequent complications included iron overload (48%) and gallstones (45%), but other complications such as aplastic crises, osteopenia/bone fragility, extramedullary hematopoiesis, postsplenectomy sepsis, pulmonary hypertension, and leg ulcers were not uncommon. Overall, 87 (34%) of 254 patients had both a splenectomy and cholecystectomy. In those who had a splenectomy without simultaneous cholecystectomy, 48% later required a cholecystectomy. Although the risk of complications increases with severity of anemia and a genotype-phenotype relationship was observed, complications were common in all patients with PK deficiency. Diagnostic testing for PK deficiency should be considered in patients with apparent congenital hemolytic anemia and close monitoring for iron overload, gallstones, and other complications is needed regardless of baseline hemoglobin. This trial was registered at www.clinicaltrials.gov as #NCT02053480.

Atypical haemolytic uraemic syndrome in a patient with sickle cell disease, successfully treated with eculizumab

Keywords: sickle cell disease; atypical haemolytic uraemic syndrome; eculizumab; thrombotic microangiopathy; complement mutations

Genotype-phenotype correlations in hereditary elliptocytosis and hereditary pyropoikilocytosis.

Hereditary elliptocytosis (HE) and hereditary pyropoikilocytosis (HPP) are heterogeneous red blood cell (RBC) membrane disorders that result from mutations in the genes encoding α-spectrin (SPTA1), β-spectrin (SPTB), or protein 4.1R (EPB41). The resulting defects alter the horizontal cytoskeletal associations and affect RBC membrane stability and deformability causing shortened RBC survival. The clinical diagnosis of HE and HPP relies on identifying characteristic RBC morphology on peripheral blood smear and specific membrane biomechanical properties using osmotic gradient ektacytometry. However, this phenotypic diagnosis may not be readily available in patients requiring frequent transfusions, and does not predict disease course or severity. Using Next-Generation sequencing, we identified the causative genetic mutations in fifteen patients with clinically suspected HE or HPP and correlated the identified mutations with the clinical phenotype and ektacytometry profile. In addition to identifying three novel mutations, gene sequencing confirmed and, when the RBC morphology was not evaluable, identified the diagnosis. Moreover, genotypic differences justified the phenotypic differences within families with HE/HPP.

Recipient priming to one RBC alloantigen directly enhances subsequent alloimmunization in mice

Individuals that become immunized to red blood cell (RBC) alloantigens can experience an increased rate of antibody formation to additional RBC alloantigens following subsequent transfusion. Despite this, how an immune response to one RBC immunogen may impact subsequent alloimmunization to a completely different RBC alloantigen remains unknown. Our studies demonstrate that Kell blood group antigen (KEL) RBC transfusion in the presence of inflammation induced by poly (I:C) (PIC) not only enhances anti-KEL antibody production through a CD4+ T-cell-dependent process but also directly facilitates anti-HOD antibody formation following subsequent exposure to the disparate HOD (hen egg lysozyme, ovalbumin, fused to human blood group antigen Duffy b) antigen. PIC/KEL priming of the anti-HOD antibody response required that RBCs express both the KEL and HOD antigens (HOD × KEL RBCs), as transfusion of HOD RBCs plus KEL RBCs or HOD RBCs alone failed to impact anti-HOD antibody formation in recipients previously primed with PIC/KEL. Transfer of CD4+ T cells from PIC/KEL-primed recipients directly facilitated anti-HOD antibody formation following (HOD × KEL) RBC transfusion. RBC alloantigen priming was not limited to PIC/KEL enhancement of anti-HOD alloantibody formation, as HOD-reactive CD4+ T cells enhanced anti-glycophorin A (anti-GPA) antibody formation in the absence of inflammation following transfusion of RBCs coexpressing GPA and HOD. These results demonstrate that immune priming to one RBC alloantigen can directly enhance a humoral response to a completely different RBC alloantigen, providing a potential explanation for why alloantibody responders may exhibit increased immune responsiveness to additional RBC alloantigens following subsequent transfusion.

Transfusion-transmitted malaria masquerading as sickle cell crisis with multisystem organ failure.

Fever accompanying vaso‐occlusive crisis is a common presentation in patients with sickle cell disease (SCD) and carries a broad differential diagnosis. Here, we report a case of transfusion‐transmitted malaria in a patient with SCD presenting with acute vaso‐occlusive crisis and rapidly decompensating to multisystem organ failure (MSOF).

Evaluation and Treatment of Thrombotic Thrombocytopenic Purpura

Thrombotic thrombocytopenic purpura (TTP) is a rare blood disorder, characterized by microangiopathic hemolytic anemia, thrombocytopenia, and varying degrees of organ ischemia from microvascular occlusion. This is an aggressive form of thrombotic microangiopathy (TMA), resulting from severe deficiency of ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin motifs 13) activity. The deficiency is either congenital (cTTP) in 5% of cases from biallelic (homozygous or compound heterozygous) mutations involving ADAMTS13 or acquired (immune-mediated TTP) in 95% of subjects due to autoantibodies against ADAMTS13. Though it is a rare disease, mortality during acute presentation remains very high. Therefore, TTP requires prompt diagnosis and immediate institution of lifesaving treatment modalities. This complex multisystem disorder is reviewed here with a focus on the diagnosis and clinical management of immune-mediated TTP, including emerging disease-modifying therapies.

Alu element insertion in PKLR gene as a novel cause of pyruvate kinase deficiency in Middle Eastern patients

Pyruvate kinase deficiency (PKD) is the most frequent red blood cell enzyme abnormality of the glycolytic pathway and the most common cause of hereditary nonspherocytic hemolytic anemia. Over 250 PKLR‐gene mutations have been described, including missense/nonsense, splicing and regulatory mutations, small insertions, small and gross deletions, causing PKD and hemolytic anemia of variable severity. Alu retrotransposons are the most abundant mobile DNA sequences in the human genome, contributing to almost 11% of its mass. Alu insertions have been associated with a number of human diseases either by disrupting a coding region or a splice signal. Here, we report on two unrelated Middle Eastern patients, both born from consanguineous parents, with transfusion‐dependent hemolytic anemia, where sequence analysis revealed a homozygous insertion of AluYb9 within exon 6 of the PKLR gene, causing precipitous decrease of PKLR RNA levels. This Alu element insertion consists a previously unrecognized mechanism underlying pathogenesis of PKD.

Contribution of alternative complement pathway to delayed hemolytic transfusion reaction in sickle cell disease

Transfusion of red blood cells (RBC) remains a primary treatment modality in patients with sickle cell disease (SCD). Repeated exposure to alloantigens on transfused RBCs can lead to alloantibody formation that can increase the risk of delayed hemolytic transfusion reaction (DHTR).[1][1] The

Prevalence and management of iron overload in pyruvate kinase deficiency: report from the Pyruvate Kinase Deficiency Natural History Study

Pyruvate kinase (PK) deficiency is the most common red cell glycolytic enzyme defect causing hereditary non-spherocytic hemolytic anemia. Current treatments are mainly supportive and include red cell transfusions and splenectomy.[1][1] Regular red cell transfusions are known to result in iron

Congenital dyserythropoietic anaemia type I diagnosed in a young adult with a history of splenectomy in childhood for presumed haemolytic anaemia

A 27-year-old African-American man presented with what was interpreted as non-immune haemolytic anaemia. He reported frequent transfusions in childhood until he underwent splenectomy at 11 years of age; he had a history of short stature treated with growth hormone in childhood and of posterior spinal fusion for scoliosis. He had recently been diagnosed with pulmonary hypertension by right heart catheterisation. A full blood count showed Hb 76 g/l, MCV 93.6 fl, MCHC 326 g/l, RDW 41.7% and absolute reticulocyte count 365 9 10/l. A peripheral blood film (top left) showed marked anisopoikilocytosis and polychromasia, macrocytes, target cells and occasional nucleated red cells. Elongated erythrocytes, appearing as double target cells (arrows), and erythrocytes with ‘double-dimple’ (arrowhead), previously seen in patients with congenital dyserythropoietic anaemia type-I (CDA-I) enrolled in the CDA Registry for North America (NCT02964494), were also noted. Genetic testing revealed twoCDAN1mutations in the patient: c.3389C>T; p.P1130L and c.2868+1C>T (top right). The patient’s mother carried only c.3389C>T, indicating that the two CDAN1 mutations in the patient are in trans. Bone marrow studies, performed at 7 and 11 years of age, had demonstrated marked erythroid hyperplasia and dyserythropoiesis with occasional binucleated erythroblasts (bottom left), although not in a number satisfying the diagnostic criteria for CDA-I. Retrospective review revealed rare but characteristic erythroblasts with chromatin bridges (bottom right). On further evaluation, he was found to have severe iron overload (liver iron concentration by Ferriscan 28 mg/g dry weight) while magnetic resonance imaging revealed multiple paraspinal and posterior mediastinalmasses representing extramedullary erythropoiesis. CDA-I is an autosomal recessive disease presenting typically in infancy or early childhood with congenital macrocytic anaemia that has features of haemolysis but suboptimal reticulocytosis, indicating ineffective erythropoiesis, which causes iron overload disproportionate to transfusion history. Diagnostic haematopathological criteria include 3–7% binucleated erythroblasts in the bone marrow and internuclear chromatin bridges. Mutations in CDAN1 and C15orf41 are causative. The disease may be transfusion-dependent; splenectomy does not sufficiently improve anaemia, but several patients have been treated successfully with interferon alpha. Rare patients have atypical features, such as the infrequent binucleated erythroblasts in this case. A high index of suspicion and use of genetic sequencing studies can accelerate diagnosis, optimise treatment and prevent life-threatening complications, such as severe iron-overload and pulmonary hypertension.