SARS-CoV-2 Infection and Anemia-A Focus on RBC Deformability and Membrane Proteomics-Integrated Observational Prospective Study.

INTRODUCTION: The multifaceted impact of COVID-19 extends beyond the respiratory system, encompassing intricate interactions with various physiological systems. This study elucidates the potential association between SARS-CoV-2 infection and anemia, with a particular emphasis on the deformability of red blood cells (RBCs), stability of hemoglobin, enzymatic activities, and proteomic profiles. METHODS: The study encompasses a cohort of 74 individuals, including individuals positive for COVID-19, a control group, and patients with other viral infections to discern the specific effects attributable to COVID-19. The analysis of red blood cells was focused on deformability measured by osmotic gradient ektacytometry, hemoglobin stability, and glycolytic enzyme activity. Furthermore, membrane proteins were examined using advanced proteomics techniques to capture molecular-level changes. RESULTS: Findings from the study suggest a correlation between anemia and exacerbated outcomes in COVID-19 patients, marked by significant elevations in d-dimer, serum procalcitonin, creatinine, and blood urea nitrogen (BUN) levels. These observations suggest that chronic kidney disease (CKD) may play a role in the development of anemia in COVID-19 patients, particularly those of advanced age with comorbidities. Furthermore, the proteomic analyses have highlighted a complex relationship between omics data and RBC parameters, enriching our understanding of the mechanisms underlying the disease. CONCLUSIONS: This research substantiates the complex interrelationship between COVID-19 and anemia, with a specific emphasis on the potential repercussions of SARS-CoV-2 infection on RBCs. The findings contribute to the growing body of evidence supporting the extensive impact of COVID-19 on RBCs.

The Pyruvate Kinase Deficiency Global Longitudinal (Peak) Registry: rationale and study design.

INTRODUCTION: Pyruvate kinase (PK) deficiency is a rare, under-recognised, hereditary condition that leads to chronic haemolytic anaemia and potentially serious secondary complications, such as iron overload, cholecystitis, pulmonary hypertension and extramedullary haematopoiesis. It is an autosomal recessive disease caused by homozygous or compound heterozygous mutations in the PKLR gene. Due to its rarity and clinical heterogeneity, information on the natural history and long-term clinical course of PK deficiency is limited, presenting major challenges to patient management, the development of new therapies and establishing disease-specific treatment recommendations. The Pyruvate Kinase Deficiency Global Longitudinal (Peak) Registry is an initiative to address the gaps in the knowledge of PK deficiency. This manuscript describes the objectives, study design and methodology for the Peak Registry. METHODS AND ANALYSIS: The Peak Registry is an observational, longitudinal, global registry of adult and paediatric patients with a genetically confirmed diagnosis of PK deficiency. The Peak Steering Committee is composed of 11 clinicians and researchers with experience in the diagnosis and management of PK deficiency from 10 countries, a patient representative and representatives from the sponsor (Agios Pharmaceuticals). The registry objective is to foster an understanding of the longitudinal clinical implications of PK deficiency, including its natural history, treatments and outcomes, and variability in clinical care. The aim is to enrol up to 500 participants from approximately 60 study centres across 20 countries over 7 years, with between 2 and 9 years of follow-up. Data will include demographics, diagnosis history, genotyping, transfusion history, relevant clinical events, medications, emergency room visits and hospitalisations. ETHICS AND DISSEMINATION: Registry protocol and informed consent forms are approved by institutional review boards/independent ethics committees at each study site. The study is being conducted in accordance with the Declaration of Helsinki. Registry data will be published in peer-reviewed journal articles and conference publications. TRIAL REGISTRATION NUMBER: NCT03481738.

Concomitant Hereditary Spherocytosis and Pyruvate Kinase Deficiency in a Spanish Family with Chronic Hemolytic Anemia: Contribution of Laser Ektacytometry to Clinical Diagnosis.

Background: Hereditary spherocytosis (HS) and pyruvate kinase deficiency (PKD) are the most common causes of hereditary chronic hemolytic anemia. Here, we describe clinical and genetic characteristics of a Spanish family with concomitant ß-spectrin (SPTB) c.647G>A variant and pyruvate kinase (PKLR) c.1706G>A variant. Methods: A family of 11 members was studied. Hematological investigation, hemolysis tests, and specific red cell studies were performed in all family members, according to conventional procedures. An ektacytometric study was performed using the osmoscan module of the Lorca ektacytometer (MaxSis. RR Mechatronics). The presence of the SPTB and PKLR variants was confirmed by t-NGS. Results: The t-NGS genetic characterization of the 11 family members showed the presence of a heterozygous mutation for the ß-spectrin (SPTB; c.647G>A) in seven members with HS, three of them co-inherited the PKLR variant c.1706G>A. In the remaining four members, no gene mutation was found. Ektacytometry allowed a clear diagnostic orientation of HS, independently from the PKLR variant. Conclusions: This family study allows concluding that the SPTB mutation, (c.647G>A) previously described as likely pathogenic (LP), should be classified as pathogenic (P), according to the recommendations for pathogenicity of the American College of Medical Genetics and the Association for Molecular Pathology. In addition, after 6 years of clinical follow-up of the patients with HS, it can be inferred that the chronic hemolytic anemia may be attributable to the SPTB mutation only, without influence of the concomitant PKLR. Moreover, only the family members with the SPTB mutation exhibited an ektacytometric profile characteristic of HS.

Red cell ektacytometry in two patients with chronic hemolytic anemia and three new α-spectrin variants.

Red blood cell (RBC) morphology is, in general, the key diagnostic feature for hereditary spherocytosis (HS) and hereditary elliptocytosis (HE). However, in hereditary pyropoikilocytosis (HPP), the severe clinical form of HE, the morphological diagnosis is difficult due to the presence of a RBC morphological picture characterized by a mixture of elliptocytes, spherocytes, tear-drop cells, and fragmented cells. This difficulty increases in new-borns and/or patients requiring frequent transfusions, making impossible the prediction of the disease course or its severity. Recently, it has been demonstrated that the measurement of osmotic gradient ektacytometry (OGE), using a laser-assisted optical rotational ektacytometer LoRRca (MaxSis, RR Mechatronics), allows a clear differentiation between HS and HE, where the truncated osmoscan curve reflects the inability of the already elliptical cells to deform further under shear stress in the face of hypotonicity. In HPP, however, the RBCs appear to have a significantly decreased ability to maintain deformability in these conditions, and the classical trapezoidal profile of HE is less evident or indistinguishable from HS. Here, two unrelated patients with hereditary hemolytic anemia (HHA) due to HPP and HS, respectively, are described with the joint inheritance of a complex set of five genetic defects. Two of these defects are novel alpha-spectrin gene (SPTA1) variants, one is a microdeletion that removes the entire SPTA1 gene, and two are well-known low-expression polymorphic alleles: α-LELY and α-LEPRA. In the HPP patient (ID1), with many circulating spherocytes, the interactions between the two SPTA1 gene variants may lead, in addition to an elongation defect (elliptocytes), to a loss of membrane stability and vesiculation (spherocytes), and RBCs appear to have a significantly decreased ability to maintain deformability in hypotonic conditions. Due to this, the classical trapezoidal profile of HE may become less evident or indistinguishable from HS. The second patient (ID2) was a classical severe form of HS with the presence of more than 20% of spherocytes and few pincered cells. The severity of clinical manifestation is due to the coinheritance of a microdeletion of chromosome 1 that removes the entire SPTA1 gene with a LEPRA SPTA1 variant in trans. The diagnostic interest of both observations is discussed.

Blood Rheological Characterization of ß-Thalassemia Trait and Iron Deficiency Anemia Using Front Microrheometry.

The purpose of this work is to develop a hematocrit-independent method for the detection of beta-thalassemia trait (ß-TT) and iron deficiency anemia (IDA), through the rheological characterization of whole blood samples from different donors. The results obtained herein are the basis for the development of a front microrheometry point-of-care device for the diagnosis and clinical follow-up of ß-TT patients suffering hematological diseases and alterations in the morphology of the red blood cell (RBC). The viscosity is calculated as a function of the mean front velocity by detecting the sample fluid-air interface advancing through a microfluidic channel. Different viscosity curves are obtained for healthy donors, ß-TT and IDA samples. A mathematical model is introduced to compare samples of distinct hematocrit, classifying the viscosity curve patterns with respect to the health condition of blood. The viscosity of the fluid at certain shear rate values varies depending on several RBC factors such as shape and size, hemoglobin (Hb) content, membrane rigidity and hematocrit concentration. Blood and plasma from healthy donors are used as reference. To validate their potential clinical value as a diagnostic tool, the viscosity results are compared to those obtained by the gold-standard method for RBC deformability evaluation, the Laser-Optical Rotational Red Cell Analyzer (LoRRCA).

Immigration and screening programs for hemoglobinopathies in Italy, Spain and Turkey.

Sickle cell disease (SCD) and thalassemias are the most common monogenic diseases in the world. The number of migrants and refugees in Europe and Turkey, in the past decade, has increased dramatically due to war, violence or prosecutions in their homeland. Prevention and management of haemoglobin disorders is well established and managed in countries where these conditions were traditionally endemic or in countries that have a longstanding tradition of receiving migrants. Therefore, preventive and diagnostic programmes regarding hemoglobinopathies in immigrant populations have been implemented. The purpose of this paper it to report a summary of the experience gained in Italy, Spain and Turkey in migrants, asylum seekers and refugees.

Rare anemias in adolescents.

Anemia can be the consequence of a single disease or an expression of external factors mainly nutritional deficiencies. Genetic issues are important in the primary care of adolescents because a genetic diagnosis may not be made until adolescence when the teenager presents with the first signs or symptoms of the condition. This situation is relatively frequent for rare anemias (RA) an important, and relatively heterogeneous group of rare diseases (RD) where anemia is the first and most relevant clinical manifestation of the disease. RA are characterized by their low prevalence (< 1 per 10,000 individuals), and, in some cases, by their complex mechanism. For these reasons, RA are little known, even among health professionals, and patients tend to remain undiagnosed or misdiagnosed for long periods of time, making it impossible to know the prognosis of the disease or to carry out genetic counseling for future pregnancies. Since this situation is an important cause of anxiety for both adolescent patients and their families, the physician's knowledge of the natural history of a genetic disease will be the key factor for the anticipatory guidance for diagnosis and clinical follow-up. RA can be due to three primary causes: 1.Bone marrow erythropoietic defects, 2. Excessive destruction of mature red blood cells (hemolysis), and 3. Blood loss (bleeding). More than 80% of RAs are hereditary, and about 20% remain undiagnosed but when their first clinical manifestations appear during childhood or adolescence, they are frequently misdiagnosed with iron deficiency. For this reason, RA are today an important clinical and social health problem worldwide.

Characterization of hereditary red blood cell membranopathies using combined targeted next-generation sequencing and osmotic gradient ektacytometry.

Hereditary red blood cell (RBC) membranopathies are characterized by mutations in genes encoding skeletal proteins that alter the membrane complex structure. Hereditary spherocytosis (HS) is the most common inherited RBC membranopathy leading to hereditary hemolytic anemia with a worldwide distribution and an estimated prevalence, in Europe, of about 1:2000 individuals. The recent availability of targeted next generation sequencing (t-NGS) and its combination with RBC deformability measured with a laser-assisted optical rotational ektacytometer (LoRRca) has demonstrated to be the most powerful contribution to lower the percentage of hereditary hemolytic anemia undiagnosed cases. In order to know the kind and frequency of RBC membrane mutations in our geographical area (Catalonia) and to better understand their pathophysiology, 42 unrelated, non-transfusion-dependent (NTD) patients with hereditary hemolytic anemia have been studied by combining t-NGS and LoRRca. The osmoscan module of LoRRca provides three rheological profiles that reflect the maximal deformability (EImax), osmotic fragility (Omin), and hydration state (Ohyper) of RBCs and contribute to a better understanding of the contribution RBC rheology to the severity of anemia. From the 42 patients studied, 37 were suspected to be a RBC membrane defect due to phenotypic characteristics and abnormal RBC morphology and, from these, in 31 patients (83.8% of cases) the mutation was identified by t-NGS. No definite diagnosis was achieved in 11 patients (26.2% of cases), including 6 out of 37 cases, with suspected membranopathy, and 5 with unclassifiable HHA. In all these undiagnosed patients, the existence of hemoglobinopathy and/or enzymopathy was ruled out by conventional methods.

European expert network on rare communicable diseases and other rare diseases linked to mobility and globalisation focused on health care provision (EURaDMoG): a feasibility study.

INTRODUCTION: In the current mobility and globalization context, there is a growing need to identify potential changes on the pattern of diseases in the European Union (EU)/European Economic Area (EEA) and provide accurate diagnosis and treatment for the population. The pattern of rare communicable diseases that can affect people returning to EU/EEA from travel abroad, visiting EU/EEA or establishing in the EU/EEA is of special relevance. The objective of this manuscript is to give an overview about the EURaDMoG study and discuss the feasibility of establishing a European network on rare communicable diseases and other rare conditions linked to mobility and globalization. METHODS: We undertook a three-steps process where we first conducted a narrative review to estimate the prevalence and incidence and to list rare communicable and non-communicable diseases linked to mobility and globalization in the EU/EEA; second, we organized an international consultation workshop with experts in the diseases previously selected; and finally, the feasibility study analysed how successful a European expert network on rare diseases linked to mobility and globalization focused on health care provision would be, accounting for different operational and also sustainability criteria. RESULTS: First, considering the areas or topics that the network should cover, it was concluded that communicable and non-communicable rare diseases linked to mobility and globalization should be differentiated. Second, since all non-communicable rare diseases linked to mobility and globalization identified are already covered by different European Reference Networks (ERNs), there is no need for them to be included in a new European network. Three scenarios were considered for establishing a potential European network for rare communicable diseases linked to Mobility and Globalisation with a focus on Health Care provision: 1) To maintain the current situation "Status Quo" scenario; 2) to create a specific European expert network (EEN) on rare communicable diseases linked to mobility and globalisation; 3) to develop a new ERN on communicable rare diseases linked to mobility and globalisation. CONCLUSIONS: Since the focus is the provision of health care, an ERN could have the potential to better boost the quality of care being facilitated by technological tools and online platforms that permit the safe and ethically acceptable exchange of data. However, this potential new network should not eclipse current existing networks and they should be complementary.

Rare Anaemias, Sickle-Cell Disease and COVID-19.

For rare haematological diseases (RHD), the first question to be answered is if patients with be- nign red blood cell (RBC) defects like haemoglobinopathies, membranopathies and enzymopathies are more vulnerable to COVID-19 infection. Up to now, there is no yet literature on the subject, but, like in general population, the presence of comorbidities such as diabetes, heart disease, pulmonary hypertension, reduced kidney and/or liver function, worsen the effects of the infection. Splenectomy may be an additional risk factor.

The Multifacets of COVID-19 in Adult Patients: A Concise Clinical Review on Pulmonary and Extrapulmonary Manifestations for Healthcare Physicians.

COVID-19 is an infectious disease caused by the SARS-CoV-2 virus. Most people with COVID-19 have a mild to moderate respiratory illness; others experience severe illness, such as COVID-19 pneumonia. The first and most accessible diagnostic information is from symptoms and signs from clinical examination. Infected patients present with a variety of manifestations. Formal diagnosis requires laboratory analysis of nose and throat samples, or imaging tests like CT scans. Emerging data suggest that coronavirus disease 2019 (COVID-19) has extrapulmonary manifestations. Sometimes these extra-respiratory manifestations may be the initial or only symptom of COVID-19, prior to fever or respiratory manifestations. In summary, our concise review shows that there is a wide range of symptoms that can be presented by COVID-19 patients. Extra-respiratory manifestations of SARS-CoV-2 infection have recently been observed in the rapidly increasing number of COVID-19 cases. Considering the broad spectrum of clinical manifestations and the increasing worldwide burden of the disease, there is an urgent need to rapidly scale up the diagnostic capacity to detect COVID-19 and its complications.

Red Blood Cell Membrane Conductance in Hereditary Haemolytic Anaemias.

Congenital haemolytic anaemias are inherited disorders caused by red blood cell membrane and cytoskeletal protein defects, deviant hemoglobin synthesis and metabolic enzyme deficiencies. In many cases, although the causing mutation might be known, the pathophysiology and the connection between the particular mutation and the symptoms of the disease are not completely understood. Thus effective treatment is lagging behind. As in many cases abnormal red blood cell cation content and cation leaks go along with the disease, by direct electrophysiological measurements of the general conductance of red blood cells, we aimed to assess if changes in the membrane conductance could be a possible cause. We recorded whole-cell currents from 29 patients with different types of congenital haemolytic anaemias: 14 with hereditary spherocytosis due to mutations in α-spectrin, ß-spectrin, ankyrin and band 3 protein; 6 patients with hereditary xerocytosis due to mutations in Piezo1; 6 patients with enzymatic disorders (3 patients with glucose-6-phosphate dehydrogenase deficiency, 1 patient with pyruvate kinase deficiency, 1 patient with glutamate-cysteine ligase deficiency and 1 patient with glutathione reductase deficiency), 1 patient with ß-thalassemia and 2 patients, carriers of several mutations and a complex genotype. While the patients with ß-thalassemia and metabolic enzyme deficiencies showed no changes in their membrane conductance, the patients with hereditary spherocytosis and hereditary xerocytosis showed largely variable results depending on the underlying mutation.

The experience of a tertiary unit on the clinical phenotype and management of hypogonadism in female adolescents and young adults with transfusion dependent thalassemia.

BACKGROUND: Transfusion-dependent ß-thalassemia (TDT) is associated with several complications necessitating a multidisciplinary approach for diagnosis, treatment and follow-up. Hypogonadism in female TDT patients is one of the most common endocrine complications, requiring hormone replacement therapy (HRT) throughout reproductive life. Little is known about the balance of benefits versus risks of treatment with sex steroids. AIM: The aim of this manuscript is to review the action and the associated adverse effects of HRT in hypogonadal TDT females. DESIGN: Retrospective medical database records from a single centre, over a period of 38 years (January 1980 to June 2018), were reviewed. STUDY POPULATION: Forty-two cases of hypogonadism in TDT females followed in a pediatric and adolescent outpatient clinics, were in included in the study. METHODS: Auxological, clinical, laboratory, hormonal and imaging investigations were reviewed, as well as all adverse events registered during HRT. MAIN RESULTS: In general, HRT was safe for most patients. There were few minor side effects and a couple of rare but serious adverse events. CONCLUSIONS: The study provides a representative clinical profile of long-term effects of HRT in hypogonadal adolescents and young adult TDT women. Our results highlight also the need for further research in other areas for which HRT may have a role.  We hope this will contribute to a wider understanding, and potential improvement, of patient safety and quality of life.

Is Increased Intracellular Calcium in Red Blood Cells a Common Component in the Molecular Mechanism Causing Anemia?

For many hereditary disorders, although the underlying genetic mutation may be known, the molecular mechanism leading to hemolytic anemia is still unclear and needs further investigation. Previous studies revealed an increased intracellular Ca2+ in red blood cells (RBCs) from patients with sickle cell disease, thalassemia, or Gardos channelopathy. Therefore we analyzed RBCs' Ca2+ content from 35 patients with different types of anemia (16 patients with hereditary spherocytosis, 11 patients with hereditary xerocytosis, 5 patients with enzymopathies, and 3 patients with hemolytic anemia of unknown cause). Intracellular Ca2+ in RBCs was measured by fluorescence microscopy using the fluorescent Ca2+ indicator Fluo-4 and subsequent single cell analysis. We found that in RBCs from patients with hereditary spherocytosis and hereditary xerocytosis the intracellular Ca2+ levels were significantly increased compared to healthy control samples. For enzymopathies and hemolytic anemia of unknown cause the intracellular Ca2+ levels in RBCs were not significantly different. These results lead us to the hypothesis that increased Ca2+ levels in RBCs are a shared component in the mechanism causing an accelerated clearance of RBCs from the blood stream in channelopathies such as hereditary xerocytosis and in diseases involving defects of cytoskeletal components like hereditary spherocytosis. Future drug developments should benefit from targeting Ca2+ entry mediating molecular players leading to better therapies for patients.

Déficit de piruvato cinasa eritrocitaria en España: estudio de 15 casos / Red cell pyruvate kinase deficiency in Spain: A study of 15 cases

Antecedentes y objetivo: El déficit de piruvato cinasa (DPK) es una enfermedad hereditaria rara, que cursa con hemólisis crónica y anemia de intensidad variable. Su heterogeneidad genética es elevada, habiéndose descrito unas 240 mutaciones diferentes. Pacientes y metodología: Se han estudiado 15 pacientes con DPK en los que se ha secuenciado la totalidad del gen PKLR, incluyendo las regiones promotora, exónicas, intrónicas flanqueantes y 3’UTR. Resultados: Según la intensidad del cuadro clínico, los pacientes se han clasificado en 3 grandes grupos: I) grave y muy grave (8 pacientes); II) moderado (2 pacientes), y III) leve (5 pacientes). Se han identificado 18 alelos diferentes, de los que 6 son mutaciones nuevas, no descritas con anterioridad, siendo la mutación PKLRc.721G > T la más prevalente (26,67%), seguida de la mutación PKLR c.1456C > T (13,33%). Trece de los 15 pacientes mostraron un genotipo doble heterocigoto y 2 homocigoto. Conclusiones: En España, la heterogeneidad del patrón genético de la PKLR continúa siendo elevada, aunque algo diferente a la observada en un estudio anterior (1998). Se concluye que la secuenciación total del gen PKLR es imprescindible tanto para la caracterización de los pacientes como para la realización del consejo genético (AU)

Background and objective: Pyruvate kinase deficiency (PKD) is a rare, inherited disease causing chronic hemolysis and anemia of varying intensity. The genetic heterogeneity of PKD is high and, to this day, over 240 different mutations have been identified. Patients and methods: 15 unrelated patients affected by PKD have been studied. PKLR gene sequencing was performed by SANGER, including the determination of promoter regions, exonic, intronic flanking and 3’UTR. Results: Patients were classified into 3 groups based on the intensity of their clinical symptoms: I) severe and very severe (8 patients); II) moderate (2 patients), and III) mild (5 patients). Six out of the 18 alleles found were new mutations which had not been described previously, with the PKLR c.721G>T mutation being the most prevalent (26.67%), followed by the PKLR c.1456C>T mutation (13.33%). Conclusions: In Spain, the genetic heterogeneity of PKLR is still high but differs from that observed in the previous study carried out in 1998. Total PKLR gene sequencing is necessary for the characterization of all patients with PKD and for genetic counseling (AU)

Criteria for assigning laboratory measurands to models for analytical performance specifications defined in the 1st EFLM Strategic Conference.

This paper, prepared by the EFLM Task and Finish Group on Allocation of laboratory tests to different models for performance specifications (TFG-DM), is dealing with criteria for allocating measurands to the different models for analytical performance specifications (APS) recognized in the 1st EFLM Strategic Conference Consensus Statement. Model 1, based on the effect of APS on clinical outcome, is the model of choice for measurands that have a central role in the decision-making of a specific disease or clinical situation and where cut-off/decision limits are established for either diagnosing, screening or monitoring. Total cholesterol, glucose, HbA1c, serum albumin and cardiac troponins represent practical examples. Model 2 is based on components of biological variation and should be applied to measurands that do not have a central role in a specific disease or clinical situation, but where the concentration of the measurand is in a steady state. This is best achieved for measurands under strict homeostatic control in order to preserve their concentrations in the body fluid of interest, but it can also be applied to other measurands that are in a steady state in biological fluids. In this case, it is expected that the "noise" produced by the measurement procedure will not significantly alter the signal provided by the concentration of the measurand. This model especially applies to electrolytes and minerals in blood plasma (sodium, potassium, chloride, bicarbonate, calcium, magnesium, inorganic phosphate) and to creatinine, cystatin C, uric acid and total protein in plasma. Model 3, based on state-of-the-art of the measurement, should be used for all the measurands that cannot be included in models 1 or 2.

Red cell pyruvate kinase deficiency in Spain: A study of 15 cases. / Déficit de piruvato cinasa eritrocitaria en España: estudio de 15 casos.

BACKGROUND AND OBJECTIVE: Pyruvate kinase deficiency (PKD) is a rare, inherited disease causing chronic hemolysis and anemia of varying intensity. The genetic heterogeneity of PKD is high and, to this day, over 240 different mutations have been identified. PATIENTS AND METHODS: 15 unrelated patients affected by PKD have been studied. PKLR gene sequencing was performed by SANGER, including the determination of promoter regions, exonic, intronic flanking and 3'UTR. RESULTS: Patients were classified into 3 groups based on the intensity of their clinical symptoms: I) severe and very severe (8 patients); II) moderate (2 patients), and III) mild (5 patients). Six out of the 18 alleles found were new mutations which had not been described previously, with the PKLR c.721G>T mutation being the most prevalent (26.67%), followed by the PKLR c.1456C>T mutation (13.33%). CONCLUSIONS: In Spain, the genetic heterogeneity of PKLR is still high but differs from that observed in the previous study carried out in 1998. Total PKLR gene sequencing is necessary for the characterization of all patients with PKD and for genetic counseling.