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.

Bone marrow transplantation corrects haemolytic anaemia in a novel ENU mutagenesis mouse model of TPI deficiency.

In this study, we performed a genome-wide N-ethyl-N-nitrosourea (ENU) mutagenesis screen in mice to identify novel genes or alleles that regulate erythropoiesis. Here, we describe a recessive mouse strain, called RBC19, harbouring a point mutation within the housekeeping gene, Tpi1, which encodes the glycolysis enzyme, triosephosphate isomerase (TPI). A serine in place of a phenylalanine at amino acid 57 severely diminishes enzyme activity in red blood cells and other tissues, resulting in a macrocytic haemolytic phenotype in homozygous mice, which closely resembles human TPI deficiency. A rescue study was performed using bone marrow transplantation of wild-type donor cells, which restored all haematological parameters and increased red blood cell enzyme function to wild-type levels after 7 weeks. This is the first study performed in a mammalian model of TPI deficiency, demonstrating that the haematological phenotype can be rescued.

Two novel mutations (p.(Ser160Pro) and p.(Arg472Cys)) causing glucose-6-phosphate isomerase deficiency are associated with erythroid dysplasia and inappropriately suppressed hepcidin.

Glucose-6-phosphate isomerase (GPI) deficiency, a genetic disorder responsible for chronic nonspherocytic hemolytic anemia, is the second most common red blood cell glycolytic enzymopathy. We report three patients from two unrelated families of Czech and Slovak origin with macrocytic hemolytic anemia due to GPI deficiency. The first patient had 15% of residual GPI activity resulting from two new heterozygous missense mutations c.478T>C and c.1414C>T leading to substitutions p.(Ser160Pro) and p.(Arg472Cys). Two other patients (siblings) inherited the same c.1414C>T p.(Arg472Cys) mutation in a homozygous constitution and lost approximately 89% of their GPI activity. Erythroid hyperplasia with dysplastic features was observed in the bone marrow of all three patients. Low hepcidin/ferritin ratio and elevated soluble transferrin receptor detected in our GPI-deficient patients suggest disturbed balance between erythropoiesis and iron metabolism contributing to iron overload.

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 adenylate kinase deficiency: characterization of recombinant mutant forms and relationship with nonspherocytic hemolytic anemia.

OBJECTIVE: Red cell adenylate kinase (AK) deficiency is a rare hereditary erythroenzymopathy associated with moderate to severe nonspherocytic hemolytic anemia and, in some cases, with mental retardation and psychomotor impairment. To date, diagnosis of AK deficiency depends upon demonstration of low enzyme activity in red blood cells and detection of mutations in AK1 gene. To investigate the molecular bases of the AK deficiency, we characterized five variants of AK1 isoenzyme-bearing mutations (118G>A, 190G>A, 382C>T, 418-420del, and 491A>G) found in AK-deficient patients with chronic hemolytic anemia. MATERIALS AND METHODS: The complete AK1 cDNA was obtained by standard procedures and using as template the reticulocyte RNA. The cDNA was cloned in a plasmid vector and the enzyme was expressed in Escherichia coli BL21(DE3)pLysS, and purified by standard protocols to homogeneity. DNA mutants bearing point mutations were obtained from the cloned wild-type cDNA using standard methods of site-directed mutagenesis, whereas the DNA mutant with deletion of codon 140 was obtained by a two-step method. RESULTS: Four mutant enzymes (Gly40Arg, Gly64Arg, Arg128Trp, Asp140del) were severely affected in activity, displaying a catalytic efficiency of four orders of magnitude lower than the wild-type; one (Tyr164Cys) was grossly perturbed in protein stability. CONCLUSIONS: The altered properties displayed by the mutant enzymes support the cause-effect relationship between AK1 mutations and hemolytic anemia.

Three cases of hereditary nonspherocytic hemolytic anemia associated with red blood cell glutathione deficiency.

Three unrelated Japanese patients with chronic nonspherocytic hemolytic anemia wer found to have marked deficiency of red blood cell (RBC) reduced glutathoine (GSH) (4.4%, 13.1%, and 6.9% of normal, respectively). A panel of RBC enzyme assays showed that one patient had decreased glutathione synthetase activity and the other two were moderately deficient in gamma-glutamylcystine synthetase. Some family members of each patient showed mild deficiency of the respective enzymes. RBCs of these patients also showed a decreased level of glutathione-S-transferase as in previously described GSH-deficient cases. Hemolytic anemia was their only manifestation, and neither 5-oxoprolinemia nor 5-oxoprolinuria, which are usually associated with to generalized type of glutathione synthetase deficiency, was noted in our patients.

Glucose-6-phosphate isomerase deficiency associated with nonspherocytic hemolytic anemia in the mouse: an animal model for the human disease.

The first two mutations causing hereditary glucose-6-phosphate isomerase (GPI) deficiency associated with chronic nonspherocytic hemolytic anemia in nonhuman mammals are described in the mouse. As in humans, the hemolytic syndrome, which is characterized by a diminished erythrocyte number, lower hematocrit, lower hemoglobin, higher number of reticulocytes and plasma bilirubin concentration, as well as increased liver- and spleen-somatic indices, was exclusively manifested in homozygous mutants. In comparison with wild type, heterozygous individuals exhibited neither hematologic differences nor alterations of other physiologic parameters, including plasma concentration of glucose, pyruvate and lactate, body weight, organo-somatic indices of liver, lung, kidney, spleen, and heart, as well as viability. Glycolytic intermediates, adenine nucleotides, and metabolic rate were not significantly altered in erythrocytes from heterozygotes. On the contrary, if allowance is made for the young erythrocyte population, homozygous mutant erythrocytes showed an increased concentration of glucose-6-phosphate and normal or decreased concentrations of glycolytic metabolites following the enzymatic block. The concentration of adenosine triphosphate and the glycolytic rate also appeared to be reduced. Homozygous anemic mice showed hepatosplenomegaly and typical adaptations to hypoxia, such as an elevated heart-somatic index and, for one mutant line, an enhanced lung-somatic index. Further, these animals were characterized by a marked reduction of body weight and an increase of lethality both correlated with the degree of enzyme deficiency in tissues. The latter findings were attributed to a reduced glycolytic capability of the whole organism caused by the enzyme defect in tissues, rather than representing secondary consequences of GPI deficiency in erythrocytes. The similarity in physicochemical and kinetic properties of the mutant murine proteins reported earlier with those of allozymes found in human GPI deficiency, as well as the comparable metabolic and physiologic consequences of this enzyme defect in mice and humans support that these murine mutants are excellent animal models for the human disease.

Combination of congenital nonspherocytic haemolytic anaemia and impairment of granulocyte function in severe glucosephosphate isomerase deficiency. A new variant enzyme designated GPI Calden.

In two siblings, children of non-consanguineous parents, glucosephosphate isomerase (GPI) deficiency was found to be the cause of recurrent haemolytic crises. Characterization of the variant enzyme found in both individuals revealed low specific activity in erythrocytes and leucocytes, increased electrophoretic mobility and pronounced thermolability. Evaluation of the electrophoretic data allows the conclusions that these siblings are compound heterozygous carriers of GPI deficiency. The new variant was designated GPI Calden. Further investigations revealed that isolated granulocytes of both siblings show marked reduction of bactericidal activity and decreased production of superoxide anion. With rare exceptions, deficiency of this enzyme was supposed to cause congenital nonspherocytic haemolytic anaemia only. Here we report on two siblings presenting with the characteristic haemolytic anaemia and a significant decrease in granulocyte function, both presumably as the result of GPI deficiency. Our data indicate that impairment of granulocyte function might be a more general feature of severe GPI deficiency than formerly noted.

Molecular basis of red cell enzymopathies associated with hereditary nonspherocytic hemolytic anemia.

In the past few years, very rapid advances have been made in the field of red cell enzymopathies associated with hereditary nonspherocytic hemolytic anemia, particularly in molecular basis. Nucleotide sequence and amino acid sequence of normal human red cell enzymes have been clarified in phosphofructokinase, aldolase, triosephosphate isomerase, phosphoglycerate kinase, pyruvate kinase, diphosphoglycerate mutase, glucose 6-phosphate dehydrogenase, adenylate kinase and adenosine deaminase. Furthermore, in aldolase-, triosephosphate isomerase-, diphosphoglycerate mutase-, glucose 6-phosphate dehydrogenase-, and adenylate kinase deficiency, single nucleotide changes which cause single amino acid substitutions and finally hemolysis, have been found.

Chronic nonspherocytic hemolytic anemia (CNSHA) and glucose 6 phosphate dehydrogenase (G6PD) deficiency in a patient with familial amyloidotic polyneuropathy (FAP). Molecular study of a new variant (G6PD Clinic) with markedly acidic pH optimum.

A new glucose-6-phosphate dehydrogenase (G6PD) variant with severe erythrocytic G6PD deficiency and a unique pH optimum is described in a young patient with chronic nonspherocytic hemolytic anemia (CNSHA) and familial amyloidotic polyneuropathy (FAP). Chronic hemolysis was present in the absence of infections, oxidant drugs or ingestion of faba beans. Residual enzyme activity was about 2.6% and 63% of normal activity in erythrocytes and leucocytes, respectively. A molecular study using standard methods showed G6PD in the patient to have normal electrophoretic mobility (at pH 7.0, 8.0 and 8.8), normal apparent affinity for substrates (Km, G6P and NADP) and a slightly abnormal utilization of substrate analogues (decreased deamino-NADP and increased 2-deoxyglucose-6-phosphate utilization). Heat stability was found to be markedly decreased (8% of residual activity after 20 min of incubation at 46 degrees C) and a particular characteristic of this enzyme was a biphasic pH curve with a greatly increased activity at low pH. Although molecular characteristics of this variant closely resemble those of G6PD Bangkok and G6PD Duarte, it can be distinguished from these and all other previously reported variants by virtue of its unusual pH curve. Therefore the present variant has been designated G6PD Clinic to distinguish it from other G6PD variants previously described.

Familial nonspherocytic hemolytic anemia in poodles.

Nonspherocytic hemolytic anemia, characterized by marked reticulocytosis, hepatosplenomegaly, hemosiderosis of reticuloendothelial organs and bone marrow myelofibrosis, and osteosclerosis, was diagnosed in 5 related Poodles. The unremitting anemia was clinically evident by 1 year of age, and was fatal as early as 3 years of age. Despite intense diagnostic endeavors including RBC fragility studies, RBC enzyme assays, and hemoglobin electrophoresis, the cause of this nonspherocytic hemolytic anemia remains to be determined.

Hereditary nonspherocytic hemolytic anemia due to a new hexokinase variant with reduced stability.

A 27-year-old woman with severe chronic hemolytic anemia was found to have reduced red cell hexokinase activity when the degree of reticulocytosis was considered. This enzyme had normal pH-dependent activity, normal Km for glucose, fructose, and mannose, normal Km for Mg adenosine triphosphate (ATP)2- and Ki for glucose-1,6-diphosphate. Furthermore, the pH-dependence and orthophosphate dependence of Ki for glucose-1,6-diphosphate were normal. However, this hexokinase was inactivated rapidly at 44 degrees C. No abnormalities were found in the red cell hexokinase isozymic pattern when it was compared with the profile obtained from cells of similar age. The hexokinase specific activity was reduced in all the red blood cell fractions obtained by density gradient ultracentrifugation; a marked difference in the distribution of cells through the gradient was evident. Among the glycolytic intermediates, a significant decrease of 2,3-diphosphoglycerate was evident. ATP and glucose 6-phosphate were also reduced when compared with cells of similar. Glucose consumption of the hexokinase-deficient cells decreased, but the rate of glucose metabolized through the hexose monophosphate shunt was unchanged. Although the total hexokinase activity in lymphocytes was only reduced by 37%, a marked hexokinase deficiency was detected in blood platelets (20% to 25% of normal activity). The parents and one of two siblings of the patient were heterozygous for the defect, with 66% to 74% of normal erythrocyte hexokinase activity and reduced heat stability of the enzyme. These results, when compared with those obtained in previously reported cases of hexokinase deficiency, provide further evidence of the broad phenotypic variability that characterizes this disorder. Furthermore, it is suggested that failure of energy generation is probably the primary cause of hemolytic anemia in hexokinase deficiency.

Platelet functions and energy metabolism in a patient with hexokinase deficiency.

We have studied the regeneration of adenosine triphosphate (ATP) in the glycolytic pathway in platelets with a 75% reduction in hexokinase (HK) activity and have investigated aggregation and Ca2+ secretion. HK-deficient platelets had a normal glycolytic flux in the resting state, but responded insufficiently to stimulation with thrombin (5 U/ml). In contrast, glycogen contents and glycogenolysis were normal. When the metabolic adenine nucleotides were labeled with 14C-adenine, the patient's platelets showed a normal adenylate energy charge and a normal level of 14C-ATP. However, the inhibitor of mitochondrial energy generation, CN-, induced a weaker fall in 14C-ATP in the patient's platelets than in the controls. Analysis of secretion markers revealed decreased amounts of granule-bound ATP and secretable Ca2+, whereas granule-bound adenosine diphosphate (ADP), beta-thromboglobulin, N-acetyl-beta-D-glucosaminidase, and beta-glucuronidase were within the normal range. Aggregation and Ca2+ secretion induced by 5 U/ml thrombin were normal and were not changed in the presence of inhibitors of mitochondrial and glycogenolytic energy generation. Aggregation was also normal at 0.1 U/ml thrombin and was independent of these inhibitors, but Ca2+ secretion was greatly impaired when mitochondrial and glycogenolytic ATP resynthesis was abolished. These findings indicate that a severe reduction in HK activity causes insufficient acceleration of the glycolytic flux during stimulation with thrombin. This leads to impaired dense granule secretion in conditions where secretion depends on concurrent ATP resynthesis and glycolysis is rate limiting.

Hereditary high-adenosine triphosphate syndrome: study of a new variant.

A new variant of hereditary hemolytic anemia in a family due to high adenosine triphosphate (ATP) is reported. The increase in ATP levels varied from 83 to 105% in the family members. Low 2,3-diphosphoglycerate levels and low 2,3-diphosphoglyceromutase activity were observed in three family members, with normal glucose-6-phosphate dehydrogenase and pyruvate kinase activity.

Three pyruvate kinase variants with increased affinity for PEP.

Three variants of pyruvate kinase are described which have marked reduction of activity associated with severe non-spherocytic haemolytic anaemia. Each variant shows a reduced K0.5 PEP (the value of the intercept of the abscissa on the Hill plot) and reduced Hill coefficient; FDP activation and ATP inhibition are less than normal and utilization of GDP is increased. The variants are slightly less inhibited by 2,3DPG than controls but require more FDP to relieve this inhibition. Cases 1 and 2 have decreased thermostability but case 3 is normal. The mutant enzymes are further distinguished by their affinity for FDP. Their kinetic and physicochemical properties are compared with other known cases with high affinity for PEP and discussed in terms of a R in equilibrium to T model model for allosteric enzymes.

Clinical features and biochemical aspects of red blood cells in Hb Hirosaki.

Hb Hirosaki is a new unstable variant in which CE 1 phenylalanine of alpha-chain is substituted by leucine. Seven patients with hemolytic anemia were found in one family and Hb Hirosaki was detected in four of them. In clinical feature some differences of severity were observed between child and adult patients. The child cases showed relatively severe symptoms with repeated hemolytic crises and drug sensitivity. Otherwise most of adult cases had only mild hemolytic process throughout their past life. The variety of clinical severity suggests that the expression of abnormal gene may be various in this disorder. The mode of inheritance seemed to be autosomal dominant and all the cases in this report were heterozygous state. Macrocytic and hypochromic anemia was characteristic in most cases and red blood cells containing Heinz bodies were dominant in peripheral blood from the splenectomized patients. Accelerated glycolysis and enhanced ATPase activity were outstanding features in the metabolism of erythrocyte in this disorder. The instability of reduced glutathione was also found in three of five cases.