The pyruvate kinase (PK) to hexokinase enzyme activity ratio and erythrocyte PK protein level in the diagnosis and phenotype of PK deficiency.

Diagnosis of pyruvate kinase deficiency (PKD), the most common cause of hereditary non-spherocytic haemolytic anaemia, remains challenging in routine practice and no biomarkers for clinical severity have been characterised. This prospective study enrolled 41 patients with molecularly confirmed PKD from nine North American centres to evaluate the diagnostic sensitivity of pyruvate kinase (PK) enzyme activity and PK:hexokinase (HK) enzyme activity ratio, and evaluate the erythrocyte PK (PK-R) protein level and erythrocyte metabolites as biomarkers for clinical severity. In this population not transfused for ≥90 days before sampling, the diagnostic sensitivity of the PK enzyme assay was 90% [95% confidence interval (CI) 77-97%], whereas the PK:HK ratio sensitivity was 98% (95% CI 87-100%). There was no correlation between PK enzyme activity and clinical severity. Transfusion requirements correlated with normalised erythrocyte ATP levels (r = 0·527, P = 0·0016) and PK-R protein levels (r = -0·527, P = 0·0028). PK-R protein levels were significantly higher in the never transfused [median (range) 40·1 (9·8-73·9)%] versus ever transfused [median (range) 7·7 (0·4-15·1)%] patients (P = 0·0014). The PK:HK ratio had excellent sensitivity for PK diagnosis, superior to PKLR exon sequencing. Given that the number of PKLR variants and genotype combinations limits prognostication based on molecular findings, PK-R protein level may be a useful prognostic biomarker of disease severity and merits further study.

Laboratory approach to investigation of anemia with a focus on pyruvate kinase deficiency.

Anemia is a major health burden worldwide and affects approximately one-third of world's population. It is not a diagnosis; it is a manifestation of an underlying pathophysiology leading to either decreased hemoglobin (Hb), hematocrit (Hct), or red blood cells (RBCs). Iron deficiency anemia is still the most common cause of anemia worldwide. The symptoms are usually due to the underlying compensatory responses to decrease in oxygen delivery to the tissues. Laboratory investigation should start with complete blood count (CBC), reticulocyte count (RC), and peripheral smear evaluation. Further testing depends on these indices, that is, iron parameters and hemoglobinopathies/thalassemia evaluation in microcytic hypochromic anemia, vitamin B12, and folic acid level in macrocytic anemia. Increased RC denotes adequate bone marrow response and points toward hemolytic process and vice versa. Anemia diagnosis can be complex and confusing for the practicing physician. This review tries to give a practical simplistic approach to the diagnosis, focusing mainly on the basic parameters, that is, CBC, RC, and peripheral smear etc. Moreover, we have also tried to provide an update on the pyruvate kinase deficiency, as there has been recent exciting development in the management of these patients.

Development of an Automated Enzymatic Method to Quantify Pyruvate Kinase in Red Blood Cells.

BACKGROUND: Pyruvate kinase (PK) deficiency is the most common cause of nonspherocytic hemolytic anemia owing to defective glycolysis. This study developed and validated an automated method to measure PK activity in red blood cells (RBCs). METHODS: PK catalyzes the reaction of phosphoenolpyruvate with ADP to form pyruvate and ATP. The pyruvate is reduced in the presence of lactate dehydrogenase and NADH to produce lactate and NAD+. The rate of absorbance decrease at 340 nm is proportional to PK activity. PK and hemoglobin (Hb) measurements were performed on a Roche cobas c501 analyzer. After establishing a k-factor, accuracy, linearity, imprecision, sensitivity, and stability were validated and the reference interval was verified. RESULTS: The k-factor was -9477. Accuracy was evaluated by method comparison (n = 56). Linear regression yielded y = 1.0x - 0.57, and R2 of 0.93. Linearity was determined by combining a high sample with hemolyzing solution in 6 different ratios. Linear regression analysis yielded y = 1.02x - 2.68, and R2 of 1.0. The assay was linear to 87 U/dL. Precision was evaluated by testing hemolysates in 3 replicates/day for 10 days. Within-run imprecision was 1.9% and 2.5% and total imprecision was 4.0% and 5.6% at 14.0 and 8.1 U/g Hb, respectively. The limit of blank was 0.0, and the limit of detection was 1.0 U/dL. Stability was determined in 4 sample types at 3 different temperatures; the changes were all <10% when compared with t0. The current PK reference interval of 4.6 to 11.2 U/g Hb was verified. CONCLUSIONS: This automated assay for quantifying PK in RBCs has acceptable performance characteristics and is fit for intended use.

Safety and Efficacy of Mitapivat in Pyruvate Kinase Deficiency.

BACKGROUND: Pyruvate kinase deficiency is caused by mutations in PKLR and leads to congenital hemolytic anemia. Mitapivat is an oral, small-molecule allosteric activator of pyruvate kinase in red cells. METHODS: In this uncontrolled, phase 2 study, we evaluated the safety and efficacy of mitapivat in 52 adults with pyruvate kinase deficiency who were not receiving red-cell transfusions. The patients were randomly assigned to receive either 50 mg or 300 mg of mitapivat twice daily for a 24-week core period; eligible patients could continue treatment in an ongoing extension phase. RESULTS: Common adverse events, including headache and insomnia, occurred at the time of drug initiation and were transient; 92% of the episodes of headache and 47% of the episodes of insomnia resolved within 7 days. The most common serious adverse events, hemolytic anemia and pharyngitis, each occurred in 2 patients (4%). A total of 26 patients (50%) had an increase of more than 1.0 g per deciliter in the hemoglobin level. Among these patients, the mean maximum increase was 3.4 g per deciliter (range, 1.1 to 5.8), and the median time until the first increase of more than 1.0 g per deciliter was 10 days (range, 7 to 187); 20 patients (77%) had an increase of more than 1.0 g per deciliter in the hemoglobin level at more than 50% of visits during the core study period, with improvement in markers of hemolysis. The response was sustained in all 19 patients remaining in the extension phase, with a median follow-up of 29 months (range, 22 to 35). Hemoglobin responses were observed only in patients who had at least one missense PKLR mutation and were associated with the red-cell pyruvate kinase protein level at baseline. CONCLUSIONS: The administration of mitapivat was associated with a rapid increase in the hemoglobin level in 50% of adults with pyruvate kinase deficiency, with a sustained response during a median follow-up of 29 months during the extension phase. Adverse effects were mainly low-grade and transient. (Funded by Agios Pharmaceuticals; ClinicalTrials.gov number, NCT02476916.).

A New Variant of PKLR Gene Associated With Mild Hemolysis may be Responsible for the Misdiagnosis in Pyruvate Kinase Deficiency.

Pyruvate kinase deficiency (PKD) is the most common glycolytic defect leading to hemolytic anemia. PKD is caused by the mutations in the PKLR gene; however, the detection of a decreased PK activity should be first measured for rapid diagnosis. We report here the case of a 1-year-old girl with mild hemolysis and PKD. At the time of the study, the patient showed a hemoglobin level of 9.5 g/dL, mean corpuscular volume of 93 fL, reticulocyte of 6.7%, and lactate dehydrogenase of 218 IU/L. Peripheral blood smear showed polychromasia, anisocytosis, tear drop cells, fragmented eyrtrocytes, and target cells. When a biochemical analysis was performed in our patient and her parents who had consanguinity, a decreased PK activity was detected in the patient and her father. After the molecular study of PKLR gene, a new homozygote variant, c.1708G>T (pVal570Leu), was found in our patient and her father. Her father had a misdiagnosis of Gilbert syndrome because he had unconjugated hyperbilirubinemia and not anemia. Her mother was also a carrier of the mutation in heterozygous state. Patients presenting with hemolytic anemia, either severe or mild hemolytic anemia, should be screened for PKD in the first year of life. Patients with mild hemolytic findings can be followed-up with misdiagnoses.

Addressing the diagnostic gaps in pyruvate kinase deficiency: Consensus recommendations on the diagnosis of pyruvate kinase deficiency.

Pyruvate kinase deficiency (PKD) is the most common enzyme defect of glycolysis and an important cause of hereditary, nonspherocytic hemolytic anemia. The disease has a worldwide geographical distribution but there are no verified data regarding its frequency. Difficulties in the diagnostic workflow and interpretation of PK enzyme assay likely play a role. By the creation of a global PKD International Working Group in 2016, involving 24 experts from 20 Centers of Expertise we studied the current gaps in the diagnosis of PKD in order to establish diagnostic guidelines. By means of a detailed survey and subsequent discussions, multiple aspects of the diagnosis of PKD were evaluated and discussed by members of Expert Centers from Europe, USA, and Asia directly involved in diagnosis. Broad consensus was reached among the Centers on many clinical and technical aspects of the diagnosis of PKD. The results of this study are here presented as recommendations for the diagnosis of PKD and used to prepare a diagnostic algorithm. This information might be helpful for other Centers to deliver timely and appropriate diagnosis and to increase awareness in PKD.

[How I do in front of an hemolytic anemia of unknown etiology?] / Que faire devant une anémie hémolytique sans étiologie retrouvée ?

The most frequent causes of hemolytic anemias are immune or infectious diseases, drug induced hemolysis, thrombotic microangiopathies, hereditary spherocytosis, glucose-6-phosphate dehydrogenase or pyruvate kinase deficiencies, thalassemia's and sickle cell disease. Sometimes no cause is found because a rarer etiology is involved. The goal of this review is to remember some unfrequent constitutional or acquired causes and to point out difficulties to avoid wrong interpretations of analysis results.

Screening of hereditary spherocytosis and pyruvate kinase deficiency by automated blood count using erythrocytic and reticulocytic parameters.

INTRODUCTION: Development of additional parameters for complete blood count has emerged in recent hematology analyzers, leading to many publications. However, few studies have been conducted on advanced RBC parameters and hemolytic anemias. We investigated the interest of Sysmex unique parameters, MicroR and HypoHe, as well as the immature fraction of reticulocytes (IRF) in combination with complete blood and reticulocyte count, for screening hereditary spherocytosis (HS) and pyruvate kinase deficiency. METHODS: We analyzed 182 samples using Sysmex XE-5000 analyzers from a cohort of red cell disorder patients from the Rouen University Hospital. These included 47 HS, 17 pyruvate kinase deficiencies, sickle cell diseases and trait, ß-thalassemia minor, iron deficiencies, and 489 samples from a routine group. RESULTS: Combining five parameters (hemoglobin level, reticulocyte count, IRF, MicroR, and %HypoHe), we developed a specific screening tool for HS allowing a sensitivity of 100% and a specificity of 92.1% and a specific screening tool for pyruvate kinase deficiencies allowing a sensitivity of 100% and a specificity of 96.5%. These parameters were also found accurate in infants and in HS without anemia. CONCLUSION: We propose a costless, easy-to-use, and efficient approach to detect HS and pyruvate kinase deficiencies using Sysmex analyzers. These screening tools may help diagnosis of these disorders, help prevent complications, and result in a better management of these patients.

Cord blood transplantation in a young child with pyruvate kinase deficiency.

Unrelated cord blood transplantation (CBT) was performed for the treatment of pyruvate kinase (PK) deficiency in a female pediatric patient at the age of 1 year 7 months, who had been in severe and frequent transfusion-dependent hemolytic anemia, despite red blood cell (RBC) PK activity 5.52 IU/gHb. pyruvate kinase-liver and RBC (PK-LR) had a compound heterozygous mutation located on exon 8: c.1044G > T/c.1076G > A (K348N/R359H). Hemoglobin and RBC PK corrected to 13.5 g/dL and 9.00 IU/gHb, respectively, with gene correction at 6 months after CBT. CBT should be considered as an option for useful treatment in children with severe PK deficiency in the absence of HLA identical sibling with normal RBC PK activity.

Iron status in patients with pyruvate kinase deficiency: neonatal hyperferritinaemia associated with a novel frameshift deletion in the PKLR gene (p.Arg518fs), and low hepcidin to ferritin ratios.

Pyruvate kinase (PK) deficiency is an iron-loading anaemia characterized by chronic haemolysis, ineffective erythropoiesis and a requirement for blood transfusion in most cases. We studied 11 patients from 10 unrelated families and found nine different disease-causing PKLR mutations. Two of these mutations - the point mutation c.878A>T (p.Asp293Val) and the frameshift deletion c.1553delG (p.(Arg518Leufs*12)) - have not been previously described in the literature. This frameshift deletion was associated with an unusually severe phenotype involving neonatal hyperferritinaemia that is not typical of PK deficiency. No disease-causing mutations in genes associated with haemochromatosis could be found. Inappropriately low levels of hepcidin with respect to iron loading were detected in all PK-deficient patients with increased ferritin, confirming the predominant effect of accelerated erythropoiesis on hepcidin production. Although the levels of a putative hepcidin suppressor, growth differentiation factor-15, were increased in PK-deficient patients, no negative correlation with hepcidin was found. This result indicates the existence of another as-yet unidentified erythroid regulator of hepcidin synthesis in PK deficiency.

Erythrocyte glucose-6-phosphate dehydrogenase and pyruvate kinase activities in hemoglobin H disease.

Erythrocyte glucose-6-phosphate dehydrogenase (G6PD) and pyruvate kinase (PK) activities were studied in hemoglobin H (HbH) patients by spectrophotometric method, cytochemical method and the methemoglobin reduction (MR) test for the detection of heterozygous G6PD deficiency. G6PD deficiency was found in 7 of 64 cases (10.9%), including 3 cases of genotype alpha 1/alpha 2 and 4 cases of genotype alpha 1/CS. None of the HbH patients was found to be PK-deficient. Spectrophotometrically determined G6PD and PK activities were significantly higher in HbH patients than in normals (p less than 0.001), whereas the MR test yielded a significantly lower percentage of residual methemoglobin in HbH patients than in normals (p less than 0.05). All three methods were efficient in the detection of hemizygous G6PD deficiency in HbH patients, but not in G6PD-deficient females.

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.