[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.

Autoimmune haemolytic anaemias: A retrospective study of 93 patients

INTRODUCTION

Autoimmune haemolytic anaemia (AIHA) is an infrequent and heterogeneous disease in its pathophysiology and clinical behaviour, therefore it is generally managed empirically.

PATIENTS AND METHODS

We conducted an observational, retrospective and multicentre study of 93 patients diagnosed with AHAI in 9 Spanish hospitals between 1987 and 2017, with a median follow-up of 28 months.

RESULTS

Median age of 67 years; 85% AHAI for hot antibodies and 64% primary AHAI. The lowest haemoglobin values at diagnosis related to patients under 45 years of age and serological type IgG+C. Of the patients, 92% received first line treatment, 54% second line, and 27% third line. The warm AHAI were treated in first line with steroids, with overall responses of 83% and complete of 58%. Rituximab in monotherapy or in association with steroids was administered to 34 patients with overall responses close to 100% (complete responses 40-60%), relegating splenectomy to the third line. The immunosuppressive treatment was administered in patients with autoimmune diseases or in corticoid-dependent patients.

DISCUSSION

We found high rates of response to steroids, with very prolonged treatments that cause side effects and corticoid dependence in a third of patients. The combination of steroids with rituximab in the first line, could be indicated in patients with low levels of haemoglobin and serological type IgG+C. The high relapse rates make necessary the development of randomised studies with new drugs or the combination with existing ones, which allow longer response times and with fewer side effects.

Thrombotic Risk Detection in Patients with Polycythemia Vera: The Predictive Role of DNMT3A/TET2/ASXL1 Mutations

The development of thrombotic events is common among patients with polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). We studied the influence of pathogenic mutations frequently associated with myeloid malignancies on thrombotic events using next-generation sequencing (NGS) in an initial cohort of 68 patients with myeloproliferative neoplasms (MPN). As expected, the presence of mutations in DNMT3A, TET2, and ASXL1 (DTA genes) was positively associated with age for the whole cohort (p = 0.025, OR: 1.047, 95% CI: 1.006-1.090). Also, while not related with events in the whole cohort, DTA mutations were strongly associated with the development of vascular events in PV patients (p = 0.028). To confirm the possible association between the presence of DTA mutation and thrombotic events, we performed a case-control study on 55 age-matched patients with PV (including 12 PV patients from the initial cohort, 25 with event vs. 30 no event). In the age-matched case-control PV cohort, the presence of ≥1 DTA mutation significantly increased the risk of a thrombotic event (OR: 6.333, p = 0.0024). Specifically, mutations in TET2 were associated with thrombotic events in the PV case-control cohort (OR: 3.56, 95% CI: 1.15-11.83, p = 0.031). Our results suggest that pathogenic DTA mutations, and particularly TET2 mutations, may be an independent risk factor for thrombosis in patients with PV. However, the predictive value of TET2 and DTA mutations in ET and PMF was inconclusive and should be determined in a larger cohort.

Phenotype of mutations in the promoter region of the β-globin gene

BACKGROUND

β⁺-Thalassaemia is characterised by reduced production of β chains, which decrease can be caused by mutations in the promoter region (CACCC or TATA box), and is classified as mild or silent depending on the extent of β-globin chain reduction. In both cases, homozygotes or compound heterozygotes for these mutations usually have thalassaemia intermedia. Frequently the diagnosis is made in adulthood or even in old age. A total of 37 alterations in the promoter region have been described so far.

AIMS

In this report we describe the mutations found in the promoter region of the β-globin gene in a single hospital in Madrid.

METHODS

Between 1998 and 2015, more than 9000 blood samples were analysed for full blood count and underwent haemoglobin electrophoresis and high performance liquid chromatography. Genetic analysis of the β and Gγ-globin genes was carried out by automatic sequencing and, in the case of α genes, by multiplex PCR.

RESULTS

35 samples showed mutation in the promoter region of the β-globin gene, with a total of six different mutations identified: one in the distal CACCC box, two in the proximal CACCC box, three in the ATA box.

CONCLUSIONS

Any alterations in the proximal CACCC and TATA boxes lead to a moderate decrease in synthesis of the β-globin chain, which has been demonstrated in cases of thalassaemia intermedia that have presented in the second decade of life with a moderate clinical course.

High resolution melting analysis: a rapid and accurate method to detect CALR mutations

Background

The recent discovery of CALR mutations in essential thrombocythemia (ET) and primary myelofibrosis (PMF) patients without JAK2/MPL mutations has emerged as a relevant finding for the molecular diagnosis of these myeloproliferative neoplasms (MPN). We tested the feasibility of high-resolution melting (HRM) as a screening method for rapid detection of CALR mutations.

Methods

CALR was studied in wild-type JAK2/MPL patients including 34 ET, 21 persistent thrombocytosis suggestive of MPN and 98 suspected secondary thrombocytosis. CALR mutation analysis was performed through HRM and Sanger sequencing. We compared clinical features of CALR-mutated versus 45 JAK2/MPL-mutated subjects in ET.

Results

Nineteen samples showed distinct HRM patterns from wild-type. Of them, 18 were mutations and one a polymorphism as confirmed by direct sequencing. CALR mutations were present in 44% of ET (15/34), 14% of persistent thrombocytosis suggestive of MPN (3/21) and none of the secondary thrombocytosis (0/98). Of the 18 mutants, 9 were 52 bp deletions, 8 were 5 bp insertions and other was a complex mutation with insertion/deletion. No mutations were found after sequencing analysis of 45 samples displaying wild-type HRM curves. HRM technique was reproducible, no false positive or negative were detected and the limit of detection was of 3%.

Conclusions

This study establishes a sensitive, reliable and rapid HRM method to screen for the presence of CALR mutations.

[Hemoglobin Stanleyville II [alpha78(EF7)Asn --> Lys]. First case described in Spain]

BACKGROUND AND OBJECTIVE

Structural hemoglobinopathies are the result of mutations in the genes of globin, which determine a qualitative alteration in the expression of these genes. Most alterations do not originate any significant change, and correspond to silent or asymptomatic forms. This study proves a new case of hemoglobin (Hb) Stanleyville II.

PATIENTS AND METHOD

The propositus was a 72 years old Caucasian woman, from the Canary Islands. Her hematological data were: Hb 14.3 g/dl; hematocrit 44.4%; mean corpuscular volume 85.8 fl; mean corpuscular hemoglobin 27.7 pg; red cell distribution width 15.1%; reticulocytes 1.2%; HbA2 3.1% and HbF 1.6%. Electrophoretic studies in cellulose acetate electrophoresis at alkaline pH = 8.6 and isoelectrofocusing showed an anomalous Hb similar to HbS. The anomalous Hb did not appear in agar citrate electrophoresis (pH 6.0). The analysis by reverse phase high performance liquid chromatography for globin chains showed an X anomalous after A.

RESULTS

Molecular analysis by sequentiation of the polymerase chain reaction products genes 1 and 2 showed the mutation AAC --> AAA at CD78 of second gene 2 in heterozygote state, which leads the change of asparagine to lysine.

CONCLUSIONS

The substitution of an amino acid with neutral charge like asparagine for another one with positive charge like lysine in the segment EF, which corresponds to the external surface of the tertiary structure of the chain of globin, determines the change of charge in the chain. This allows an easy differentiation by electrophoretic and chromatographic methods. Nevertheless, owing to its position in the chain, which is not critique for the stability, solubility and affinity for the oxygen allows for silent or asymptomatic forms. The Hb Stanleyville II had been described before in black families of the Congo, Uganda, USA, Alsace and Brazil. This case represents the first case described in Spain.

Renin expression in hematological malignancies and its role in the regulation of hematopoiesis

It has been demonstrated that some myeloid blasts express renin, but normal bone marrow (BM) does not display this expression. The aim of the present work was to analyze the renin expression in different hematological malignancies and different myeloid cell lines. We investigated the expression of renin by RT-PCR in BM from patients with hematological malignancies (106 patients), in nine normal BM from healthy donors and in leukemic cell lines (K562, KU812, MEG-01, U-937 and HL60), as well in K562 cell line subjected to differentiation treatments. We have observed renin expression in cells from acute myeloid leukemia (AML), chronic myelogenous leukemia (CML) and acute lymphoblastic leukemia (ALL) cases. The highest frequency was observed in AML-non acute promyelocytic leukemia(APL) cases (47.2% of the cases). The disappearance of this expression was associated with the status of complete remission of AML. Renin is expressed in some myeloid human leukemia cell lines such as K562, KU812 and MEG-01. However, when K562 cells were treated with inducers of growth inhibition and/or differentiation, the expression did not disappear, indicating that renin expression is associated with a blastic phenotype rather than with cell proliferation. The obtained findings suggest that the renin expression could have a role on the disease development and could be used as an aberrant marker of leukemia.