A case series of distal renal tubular acidosis, Southeast Asian ovalocytosis and metabolic bone disease

The in vitro red blood cell microvesiculation exerts procoagulant activity of blood cell storage in Southeast Asian ovalocytosis

Southeast Asian ovalocytosis (SAO) is characterized by the misfolding of band 3 protein in red blood cells (RBC). The abnormal structure of the band 3 protein results in dysmorphic RBC and related functions. Previous data showed that in vitro storage under hypothermic conditions alters band 3 protein structure and function. Microvesiculation includes shedding of RBC membranes, called RBC-derived microparticles/extracellular vesicles (RMP/EVs), and storage lesions. Unfortunately, there is no evidence of RBC microvesiculation under in vitro storage conditions in heterozygous SAO individuals. This study determined the generation of REVs and procoagulant activity during the storage of SAO blood samples in southern Thailand. Venous blood was collected from eight SAO and seven healthy individuals, preserved in citrate phosphate dextrose-adenine 1 (CPDA-1) at 4 °C for 35 days. The absolute numbers of REVs and PS-expressing RBCs were analyzed using flow cytometry. The procoagulant activity of the produced extracellular vesicles was determined by a clotting time assay. The results showed a significant increase in the number of REVs and PS-expressing RBCs in the SAO blood samples. Significantly correlated PS externalization and procoagulant activity were observed in the SAO blood samples. These lines of evidence indicate that the abnormality of the Band 3 protein is possibly involved in aberrant microvesiculation, exerting procoagulant activity in vitro. Increased pools of REV production and abnormal storage lesions in SAO blood samples should be a concern. Notably, the mechanisms underlying membrane vesiculation depend on the extent of blood cell storage under hypothermic conditions.

Reticulocyte Maturation and Variant Red Blood Cells

The bone marrow produces billions of reticulocytes daily. These reticulocytes mature into red blood cells by reducing their plasma membrane by 20% and ejecting or degrading residual internal organelles, membranes and proteins not required by the mature cell. This process occurs by autophagy, protein degradation and vesiculation but is not well understood. We previously reported that Southeast Asian Ovalocytic RBCs demonstrate incomplete reticulocyte maturation and we have now extended this study to a number of other variant RBCs. By comparing the profile of a pure reticulocyte preparation of cultured red cells with these variant cells, we show that the largest of these cells, the overhydrated hereditary stomatocytosis cells, are the least mature, they barely reduced their plasma membrane and contain large amounts of proteins that should have been reduced or removed. Intermediate sized variant RBCs appear to be more mature but retain some endoplasmic reticulum and residual membrane proteins. We propose that the size and composition of these variant cell types correlate with the different stages of reticulocyte maturation and provide insight into the reticulocyte maturation process.

Prevalence and aetiologies of anaemia among first trimester pregnant women in Sri Lanka; the need for revisiting the current control strategies

BACKGROUND

The Sustainable development goals, which focus strongly on equity, aim to end all forms of malnutrition by 2030. However, a significant cause of intergenerational transfer of malnutrition, anaemia in pregnancy, is still a challenge. It is especially so in the low- and middle-income settings where possible context-specific aetiologies leading to anaemia have been poorly explored. This study explores the prevalence of etiological factors significantly contributing to anaemia in pregnancy in Sri Lanka, a lower-middle-income country with a high prevalence of malnutrition albeit robust public health infrastructure.

METHODS

All first-trimester pregnant women registered in the public maternal care programme in the Anuradhapura district from July to September 2019 were invited to participate in Rajarata Pregnancy Cohort (RaPCo). After a full blood count analysis, high-performance liquid chromatography, peripheral blood film examination, serum B12 and folate levels were performed in anaemic participants, guided by an algorithm based on the red cell indices in the full blood count. In addition, serum ferritin was tested in a random subsample of 213 participants. Anaemic women in this subsample underwent B12 and folate testing.

RESULTS

Among 3127 participants, 14.4% (95%CI 13.2-15.7, n = 451) were anaemic. Haemoglobin ranged between 7.4 to 19.6 g/dl. 331(10.6%) had mild anaemia. Haemoglobin ≥13 g/dl was observed in 39(12.7%). Microcytic, normochromic-normocytic, hypochromic-normocytic and macrocytic anaemia was observed in 243(54%), 114(25.3%), 80(17.8%) and two (0.4%) of full blood counts in anaemic women, respectively. Microcytic anaemia with a red cell count ≥5 * 106 /μl demonstrated a 100% positive predictive value for minor haemoglobinopathies. Minor hemoglobinopathies were present in at least 23.3%(n = 105) of anaemic pregnant women. Prevalence of iron deficiency, B12 deficiency and Southeast Asian ovalocytosis among the anaemic was 41.9% (95%CI 26.4-59.2), 23.8% (95%CI 10.6-45.1) and 0.9% (95%CI 0.3-2.3%), respectively. Folate deficiency was not observed.

CONCLUSION

Even though iron deficiency remains the primary cause, minor hemoglobinopathies, B 12 deficiency and other aetiologies substantially contribute to anaemia in pregnancy in this study population. Public health interventions, including screening for minor hemoglobinopathies and multiple micronutrient supplementation in pregnancy, should be considered in the national programme for areas where these problems have been identified.