Mortality among US veterans with a physician-documented diagnosis of pyruvate kinase deficiency

Real-world studies of pyruvate kinase (PK) deficiency and estimates of mortality are lacking. This retrospective observational study aimed to identify patients with PK deficiency and compare their overall survival (OS) to that of a matched cohort without PK deficiency. Patients with ≥1 diagnosis code related to PK deficiency were selected from the US Veterans Health Administration (VHA) database (01/1995-07/2019); patients with a physician-documented diagnosis were included (PK deficiency cohort; index: date of first diagnosis code related to PK deficiency). Patients in the PK deficiency cohort were matched 1:5 to patients from the general VHA population (non-PK deficiency cohort; index: random visit date during match's index year). OS from index was compared between the two cohorts. Eighteen patients in the PK deficiency cohort were matched to 90 individuals in the non-PK deficiency cohort (both cohorts: mean age 57 years, 94% males; median follow-up 6.0 and 8.0 years, respectively). At follow-up, patients in the non-PK deficiency cohort had significantly longer OS than the PK deficiency cohort (median OS: 17.1 vs. 10.9 years; hazard ratio: 2.3; p = 0.0306). During their first-year post-index, 75% and 40% of the PK deficiency cohort had laboratory-confirmed anemia and iron overload, respectively. Among patients who died, cause of death was highly heterogeneous. These results highlight the increased risk of mortality and substantial clinical burden among patients with PK deficiency. While the intrinsic characteristics of the VHA database may limit the generalizability of the results, this is the first real-world study to characterize mortality in patients with PK deficiency.

Diagnosis and management of pyruvate kinase deficiency: international expert guidelines

Pyruvate kinase (PK) deficiency is the most common cause of chronic congenital non-spherocytic haemolytic anaemia worldwide, with an estimated prevalence of one in 100 000 to one in 300 000 people. PK deficiency results in chronic haemolytic anaemia, with wide ranging and serious consequences affecting health, quality of life, and mortality. The goal of the International Guidelines for the Diagnosis and Management of Pyruvate Kinase Deficiency was to develop evidence-based guidelines for the clinical care of patients with PK deficiency. These clinical guidelines were developed by use of GRADE methodology and the AGREE II framework. Experts were invited after consideration of area of expertise, scholarly contributions in PK deficiency, and country of practice for global representation. The expert panel included 29 expert physicians (including adult and paediatric haematologists and other subspecialists), geneticists, laboratory specialists, nurses, a guidelines methodologist, patients with PK deficiency, and caregivers from ten countries. Five key topic areas were identified, the panel prioritised key questions, and a systematic literature search was done to generate evidence summaries that were used in the development of draft recommendations. The expert panel then met in person to finalise and vote on recommendations according to a structured consensus procedure. Agreement of greater than or equal to 67% among the expert panel was required for inclusion of a recommendation in the final guideline. The expert panel agreed on 31 total recommendations across five key topics: diagnosis and genetics, monitoring and management of chronic complications, standard management of anaemia, targeted and advanced therapies, and special populations. These new guidelines should facilitate best practices and evidence-based PK deficiency care into clinical practice.

Neonatal Thrombocytopenia as a Presenting Finding in de novo Pyruvate Kinase Deficiency

Thrombocytopenia is a common laboratory abnormality encountered in critically ill neonates. The broad differential for thrombocytopenia, and its association with potentially severe neonatal pathology, often presents a diagnostic dilemma prompting extensive evaluation. Hemolysis due to red cell enzymopathies is a rare cause of neonatal thrombocytopenia that is typically brief and self-limiting. Here, we present a case of thrombocytopenia, refractory to transfusion, associated with anemia and hyperbilirubinemia in a neonate with pyruvate kinase deficiency (PKD) arising from compound heterozygous PKLR mutations. The nature of the thrombocytopenia in this patient created considerable diagnostic uncertainty, which was ultimately resolved by whole-exome sequencing. This case emphasizes that inherited red cell defects, such as PKD, are important to consider in cases of neonatal thrombocytopenia.

Pyruvate kinase deficiency mimicking congenital dyserythropoietic anemia type I

BACKGROUND

Pyruvate kinase (PK) deficiency is the most common enzyme abnormality in the glycolytic pathway. Here, we describe two siblings with PK deficiency that mimicked congenital dyserythropoietic anemia (CDA) type I.

CASE

The siblings were referred to our hospital for evaluation of anemia when they were newborns. Their PK enzyme activities were normal. Their bone marrow aspirations and electron microscopies showed CDA-like findings. A CDA panel with next-generation sequencing showed no mutation. Though their PK enzyme levels were normal, a molecular study of the PKLR gene showed a homozygous variant c.1623G > C (p.Lys541Asn) in exon 12 of our patients.

CONCLUSIONS

Although the diagnosis of pyruvate kinase deficiency is difficult, it can be confused with many other diagnoses. Bone marrow findings of these cases are similar to congenital dyserythropoietic anemia. In patients with normal pyruvate kinase enzyme levels, the diagnosis cannot be excluded and genetic analysis is required.

[Consensus document for the diagnosis and treatment of pyruvate kinase deficiency]

Pyruvate kinase (PK) deficiency is the second most frequent enzymopathy and the most common cause of chronic hereditary non-spherocytic haemolytic anaemia. Its global prevalence is underestimated due to low clinical suspicion of mild cases, associated with difficulties in the performance and interpretation of PK enzymatic activity assays. With the advent of next generation sequencing techniques, a better diagnostic approach is achieved. Treatment remains based on red blood cell transfusions and splenectomy, with special attention to iron overload, not only in transfusion-dependent patients. Nowadays, allogeneic hematopoietic stem cell transplantation is the only curative treatment, recommended only in selected cases of severely affected patients with an HLA-identical donor. Novel pharmacological and gene therapies are in clinical trials, with promising results. In this article, the Spanish Erythropathology Group reviews the current situation of PK deficiency, paying special attention to the usefulness of different diagnostic techniques and to actual and emerging treatments.

Molecular heterogeneity of pyruvate kinase deficiency

Red cell pyruvate kinase (PK) deficiency is the most common glycolytic defect associated with congenital non-spherocytic hemolytic anemia. The disease, transmitted as an autosomal recessive trait, is caused by mutations in the PKLR gene and is characterized by molecular and clinical heterogeneity; anemia ranges from mild or fully compensated hemolysis to life-threatening forms necessitating neonatal exchange transfusions and/or subsequent regular transfusion support; complications include gallstones, pulmonary hypertension, extramedullary hematopoiesis and iron overload. Since identification of the first pathogenic variants responsible for PK deficiency in 1991, more than 300 different variants have been reported, and the study of molecular mechanisms and the existence of genotype-phenotype correlations have been investigated in-depth. In recent years, during which progress in genetic analysis, next-generation sequencing technologies and personalized medicine have opened up important landscapes for diagnosis and study of molecular mechanisms of congenital hemolytic anemias, genotyping has become a prerequisite for accessing new treatments and for evaluating disease state and progression. This review examines the extensive molecular heterogeneity of PK deficiency, focusing on the diagnostic impact of genotypes and new acquisitions on pathogenic non-canonical variants. The recent progress and the weakness in understanding the genotype-phenotype correlation, and its practical usefulness in light of new therapeutic opportunities for PK deficiency are also discussed.

Epidemiological Study of Hereditary Hemolytic Anemia in the Korean Pediatric Population during 1997-2016: a Nationwide Retrospective Cohort Study

BACKGROUND

Hereditary hemolytic anemia (HHA) is a rare disease characterized by premature red blood cell (RBC) destruction due to intrinsic RBC defects. The RBC Disorder Working Party of the Korean Society of Hematology established and updated the standard operating procedure for making an accurate diagnosis of HHA since 2007. The aim of this study was to investigate a nationwide epidemiology of Korean HHA.

METHODS

We collected the data of a newly diagnosed pediatric HHA cohort (2007-2016) and compared this cohort's characteristics with those of a previously surveyed pediatric HHA cohort (1997-2006) in Korea. Each participant's information was retrospectively collected by a questionnaire survey.

RESULTS

A total of 369 children with HHA from 38 hospitals distributed in 16 of 17 districts of Korea were investigated. RBC membranopathies, hemoglobinopathies, RBC enzymopathies, and unknown etiologies accounted for 263 (71.3%), 59 (16.0%), 23 (6.2%), and 24 (6.5%) of the cases, respectively. Compared to the cohort from the previous decade, the proportions of hemoglobinopathies and RBC enzymopathies significantly increased (P < 0.001 and P = 0.008, respectively). Twenty-three of the 59 hemoglobinopathy patients had immigrant mothers, mostly from South-East Asia.

CONCLUSION

In Korea, thalassemia traits have increased over the past 10 years, reflecting both increased awareness of this disease and increased international marriages. The enhanced recognition of RBC enzymopathies is due to advances in diagnostic technique; however, 6.5% of HHA patients still do not have a clear diagnosis. It is necessary to improve accessibility of diagnosing HHA.

Congenital Hemolytic Anemia

Red blood cell (RBC) destruction can be secondary to intrinsic disorders of the RBC or to extrinsic causes. In the congenital hemolytic anemias, intrinsic RBC enzyme, RBC membrane, and hemoglobin disorders result in hemolysis. The typical clinical presentation is a patient with pallor, anemia, jaundice, and often splenomegaly. The laboratory features include anemia, hyperbilirubinemia, and reticulocytosis. For some congenital hemolytic anemias, splenectomy is curative. However, in other diseases, avoidance of drugs and toxins is the best therapy. Supportive care with transfusions are also mainstays of therapy. Chronic hemolysis often results in the formation of gallstones, and cholecystectomy is often indicated.

Anemia in the Neonate: The Differential Diagnosis and Treatment

Anemia is a common problem in the neonatal period. Presenting symptoms may suggest numerous possible diagnoses ranging from anemia seen as a normal part of development to anemia due to critical pathology. An illustrative case is presented to highlight the appropriate evaluation of the neonate with significant anemia. Several important features of the evaluation of neonatal anemia are highlighted. The constellation of signs and symptoms that occur in conjunction with the anemia are critical for the evaluation. The evaluation should be performed in a step-wise process that starts by eliminating common causes of anemia. Manual review of the peripheral blood smear with a hematologist can be helpful.

Molecular and clinical heterogeneity in pyruvate kinase deficiency in India

We studied the PK-LR gene in 10 unrelated Indian patients with congenital haemolytic anemia associated with erythrocyte pyruvate kinase deficiency. The patients had a variable presentation ranging from a very mild compensated hemolysis to severe anemia. Nine different mutations were detected among the 20 mutated alleles identified: one deletion (c.1042-1044del) p.Lys348del and eight single-nucleotide (nt) substitutions resulting in amino acid exchanges c.397A>G (p.Asn133Asp), c.992A>G (p.Asp331Gly), c.1072G>A (p.Gly358Arg), c.1076G>A (p.Arg359His), c.1219G>A (p.Glu407Lys), c.1241C>T (p.Pro414Leu), c.1436G>A (p.Arg479His) and c.1529G>A (p.Arg510Gln) were identified. Although all the exons, the flanking regions and the promoter region were sequenced in all cases, we failed to detect the second expected mutation in two subjects. Two mutations [c.397A>G; c.1241C>T] were novel. These novel missense mutations involved highly conserved amino acids. Two mutations were identified for the first time in the homozygous state globally (c1042-1044del; c.1072G>A) and two other mutations were identified for the first time in our population (c.1076G>A; c.1529G>A). This study along with our earlier report suggests that the most frequent mutations in India would appear to be c.1436G>A (18.33%), followed by c.992A>G (11.66%) and c.1456C>T (11.66%). Structural implications of amino acid substitutions were correlated with the clinical phenotypes seen.

A case of hereditary spherocytosis misdiagnosed as pyruvate kinase deficient hemolytic anemia

BACKGROUND

Hereditary spherocytosis (HS) and pyruvate kinase (PK) deficiency are the most common causes of congenital hemolytic anemia. We describe a case of HS with defective PK activity initially misdiagnosed as PK deficiency.

METHODS

Hematologic investigation, SDS-PAGE analysis of red cell membrane proteins and sequencing of the PKLR gene were performed.

RESULTS

The molecular characterization of the PKLR gene showed a heterozygous mutation 994G > A (Gly332Ser) associated with the promoter substitution -148C > T, whose role in the pathophysiology of PK deficiency is debated. Further investigations revealed spectrin deficiency; the family study demonstrated that the hemolysis was exclusively attributable to HS.

CONCLUSIONS

The present case pinpoints to the need for extensive family investigations to correctly diagnose chronic hemolytic anemia, in particular when molecular characterization does not fully explain the clinical phenotype.

Screening for disorders of pyruvate metabolism by measuring the ratio of the rates of lactate production and pyruvate decarboxylation in cultured skin fibroblasts

We assayed the rates of lactate production from [1-14C]pyruvate and decarboxylation of [1-14C]pyruvate in cultured skin fibroblasts from 8 patients with disorders of pyruvate metabolism and 16 control subjects. The disorders of pyruvate metabolism could be more readily detected by measuring the ratio between the rates of lactate production and pyruvate decarboxylation by cultured skin fibroblasts than by measuring either the rate in isolation.

Diagnosis of pyruvate kinase deficiency in a transfusion-dependent patient with severe hemolytic anemia

In a 2-yr old girl a hemolytic anemia was present since birth requiring multiple blood transfusions. Pyruvate kinase deficiency was suspected on the basis of a marginal enzyme activity, but could not be established due to the presence of massive numbers of donor cells in her peripheral blood. However, by density fractionation we succeeded in the isolation of a small fraction of the patient's own cells, in which a severe pyruvate kinase deficiency could be detected. In contrast hexokinase and glucose-6-phosphate dehydrogenase activities were extremely high, which is indicative that a very immature cell population is present in this fraction. In immunofluorescence studies a clear crossreaction was apparent with anti M2-type pyruvate kinase antibodies, whereas only a faint reaction with anti L-type could be detected. Despite the presence of a slight amount of L-type immunoreactive material, the residual activity in the patient's cell fraction could only be attributed to M2-type pyruvate kinase as was shown by cellulose acetate electrophoresis.

Determination of [U-13C]glucose turnover into various metabolite pools for the differential diagnosis of lactic acidemias

Stable-isotope tracer experiments performed in vitro are evaluated for their utility in differentiating between pyruvate dehydrogenase and cytochrome oxidase deficiencies, two of several enzyme defects commonly associated with the lactic acidemias. Fibroblasts of enzyme-deficient individuals and of age-matched controls are grown in medium containing [U-13C]glucose. Direct analysis of cells and conditioned culture medium provides only minor differences in the organic acid/amino acid GC-MS profiles, making differentiation of enzyme defects difficult by this method. However, differences have been found in the glucose turnover into various cell metabolites, making differentiation of these two enzyme defects possible. The cellular pool of glutamic acid experiences 13C-enrichment in both the control and cytochrome oxidase deficient lines, but not in the pyruvate dehydrogenase-deficient line. The cellular pool of an unknown, possibly an aminopentose sugar, on the other hand, experiences 13C-enrichment in the pyruvate dehydrogenase and control lines, but not in the cytochrome oxidase line. These observations, as well as other differences in the extent of enrichment into various metabolite pools, suggest that this stable-isotope approach, in vitro, is feasible and may allow these two enzyme defects to be differentiated in a definitive manner. Such stable-isotope experiments are easy to carry out with cultured cells and are inexpensive. Applications of the technique to other genetic disorders might be appropriate.