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

Abstract

Background: Familial distal renal tubular acidosis (dRTA) associated with mutations of solute carrier family 4 membrane − 1 (SLC4A1) gene could co-exist with red cell membrane abnormality, Southeast Asian ovalocytosis (SAO). Although this association is well described in Southeast Asian countries, it is less frequently found in Sri Lanka. Case presentation: We describe six patients who had dRTA co-existing with SAO. All of them initially presented with severe hypokalemia and paralysis. They presented within a period of six months to the Teaching Hospital Anuradhapura, Sri Lanka. All had metabolic acidosis indicated by low serum bicarbonate. Three of them were having underlying chronic kidney disease as well. Those three patients had mixed high and normal anion gap metabolic acidosis indicated by low delta ratio. In all dRTA was confirmed by presence of normal anion gap, hyperchloraemia, high urine pH and positive urine anion gap. Examination of blood films of all of them revealed presence of stomatocytes and macro-ovalocytosis compatible with SAO. In relation to complications of dRTA, two patients had medullary nephrocalcinosis. Three patients had biochemical evidence of osteomalacia, with two of them having radiological evidence of diffuse osteosclerosis. One patient had secondary hyperparathyroidism and a pathological fracture. Conclusions: Erythrocyte in SAO is exceptionally rigid and this abnormality is said to be evolved as it protects against Plasmodium vivax malaria and cerebral malaria cause by Plasmodium falciparum. Although two families of SAO was described earlier, SAO and dRTA combination was reported only once in a patient from Anuradhapura district. Distal renal tubular acidosis, SAO combination and its related complications including nephrocalcinosis, chronic kidney disease and metabolic bone disease was not described in Sri-Lankan literature. This case series emphasize the importance of investigating recurrent/ chronic hypokalemia to diagnose dRTA and its associations, as early correction of acidosis could prevent development of chronic kidney disease and metabolic bone disease.

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

“…South-East Asian Ovalocytosis has been reported from Sri Lanka previously. This is the first study reporting the significance of south-east Asian ovalocytosis in Sri Lankan pregnant women [73,74]. One per cent of anaemic first trimester women had this condition.…”

Reticulocyte Maturation and Variant Red Blood Cells

“…The MCV for the heterozygous SAO sample was in fact lower than the standard range (78fL). MCVs for SAO RBCs in the literature vary enormously and this is because very often SAO is reported in conjunction with other conditions, e.g., thalassemia, where the MCV is low ( Yamsri et al, 2021 ) or distal renal tubular acidosis where the MCV is high ( Gunaratne et al, 2020 ). However, it is clear from heterozygous SAO RBC films that the double stoma, macro-ovalocytes are large (100-120fL; Garnett and Bain, 2013 ).…”

Respiratory muscle paralysis in a patient with hypokalemia associated with Southeast Asian ovalocytosis: A case report

“…In Sri Lanka, there is a cluster of the population with renal tubular acidosis associated with southeast Asian ovalocytosis especially concentrated in North Central province (6). Exact data is lacking about the incidence and prevalence of southeast Asian ovalocytosis among Sri Lankan population.…”