https://www.labmed.theclinics.com/article/S0272-2712(14)00100-0/pdf

Clinical Utility of Reticulocyte Parameters

The reticulocyte count reflects the erythropoietic activity of the bone marrow and is thus useful in both the diagnosis of anemias and in monitoring bone marrow response to therapy. Starting in the mid-1990s, automated flow-cytometric analysis has replaced traditional microscopic quantitation of reticulocytes. Reticulocyte analysis now includes measurements mRNA content and the maturity of reticulocytes, cell volume, hemoglobin concentration and content. The immature reticulocyte fraction is a reliable early predictor of hematopoietic engraftment following allogeneic stem cell transplantation, while the reticulocyte hemoglobin content provides an indirect measure of the functional iron available for new red blood cell production over the previous 3-4 days. Especially in anemic newborns, reticulocyte analysis is useful to help clinicians follow erythropoietic changes, to monitor response to recombinant human erythropoietin therapy, to gauge transfusion needs, and to evaluate jaundice. Despite improved accuracy and precision, significant problems still persist in maintaining adequate levels of precision and comparability across different laboratories. In the absence of better laboratory standardization, having a single reference range for the parameters provided by flow-cytometric studies of reticulocytes remains problematic.

Automated reticulocyte counting: state of the art and clinical applications in the evaluation of erythropoiesis

Glycolysis is the most important source of energy in red cells and working muscles. Inherited defects of glycolysis can cause hemolytic anemia, neurologic abnormalities, and myopathy with exercise ...

https://www.nejm.org/doi/pdf/10.1056/NEJM199604253341705

Inherited Metabolic Myopathy and Hemolysis Due to a Mutation in Aldolase A

Most of the metabolic needs of erythrocytes are covered by glycolysis, the oxidative pentose phosphate pathway and the glutathione cycle. Hereditary enzyme deficiencies of all these pathways have been identified, among which glucose-6-phosphate isomerase (GPI) deficiency is the second most frequent erythroenzymopathy in glycolysis, being associated with non-spherocytic haemolytic anaemia of variable severity. This autosomal recessive genetic disorder may be associated in some cases with neurological impairment. GPI is a dimeric enzyme that catalyses the reversible interconversion of fructose-6-phosphate and glucose-6-phosphate. Virtually all the mutant gene products reported are characterized by marked instability and normal substrate affinities, but altered catalytic activity and electrophoretic migration rates. At the nucleotide level, 29 mutations have been reported. This chapter reviews (a) the clinical pattern of the condition; (b) biochemical and molecular studies; (c) structure-function relationships; (d) the molecular basis of neurological dysfunctions sometimes associated with GPI deficiency; and (e) the correlation between the severity of the anaemia and the molecular defect.

Glucose-6-phosphate isomerase deficiency

The authors report a case of hydrops fetalis due to severe pyruvate kinase deficiency, the most unusual clinical manifestation of this disease.

/pdf/hydrops-fetalis-associated-with-erythrocyte-pyruvate-kinase-eudv0wzn7j.pdf

Hydrops fetalis associated with erythrocyte pyruvate kinase deficiency.

The separation of red blood cells into reticulocytes and young and old erythrocytes enables investigations of fractions with different contents of reticulocytes. Activities of hexokinase, glucose phosphate isomerase, phosphofructokinase, pyruvate kinase and glucose-6-phosphate dehydrogenase showed a linear relationship to reticulocyte counts. The dependence of these enzyme activities on the age of the red blood cells exhibited a strong decline from the reticulocyte to the young erythrocyte stage followed by only little further loss of activity, thus leading to a biphasic decay of enzyme activities. By linear regression analysis enzyme activities in erythrocytes (AE) and reticulocytes (AR) could be evaluated. The activity of a given enzyme in the reticulocyte exceeded that of the erythrocyte; the quotient AR/AE represents the decline of enzyme activity from the reticulocyte to the erythrocyte stage. This value AR/AE is 16.7 for pyruvate kinase and 9.4 for hexokinase and thus considerably higher than that for the other enzymes investigated (glucose phosphate isomerase: 2.9, phosphofructokinase: 4.3, glucose-6-phosphate dehydrogenase: 4.5). In patients suffering from erythrocyte enzymopathies, the AR/AE for pyruvate kinase was 16.2 and thus almost identical to the normal enzyme. Calibration curves where the enzyme activity is plotted versus the fraction of reticulocytes enable the determination of normal activity of a given erythrocyte enzyme depending on the content of reticulocytes in red blood cell suspensions. Thus an unambiguous diagnosis of enzyme defects irrespective of reticulocyte counts becomes possible.

G De Maeyer

Papers

On the diagnosis of erythrocyte enzyme defects in the presence of high reticulocyte counts.