ISBT Science Series (2018) 0, 1–9 CONGRESS REVIEW © 2018 International Society of Blood Transfusion DOI: 10.1111/voxs.12444 NONE TOO S.M.A.LL: the global challenge of severe malarial anaemia and its transfusion support Christine Cserti-Gazdewich University Health Network/University of Toronto, Toronto, ON, Canada Received: 4 July 2018, revised 1 August 2018, accepted 3 August 2018 In endemic areas, the burden of malaria and anaemia converge together upon children, with severe malarial anaemia (SMA) accounting disproportionately for demands on limited blood supplies. The attributable morbidity and mortality from SMA remain high, and improved outcomes hinge in part on the timeliness, sufficiency and safety of transfusion support. The pathogenesis of SMA is com- plex, and depreciation kinetics (towards syndrome-defining haemoglobin levels of <50 g/l) occur acutely or insidiously, and in relation to the parasite burden and host response. Beyond haemolysis of parasitized erythrocytes, mechanisms of bystander loss and reduced erythropoiesis figure prominently, with parallels to hyperhaemolysis syndrome. Involuntarily undertransfused children with SMA in low-income countries (LIC) differ from those adults in high-income countries (HIC) who deliberately renounce transfusion. Despite youth-related advantages in the power to adapt to anaemia, critical reductions in oxygen-carrying capacity illustrate the hierarchical impacts of organ anoxia, be it in terminal cardiorespi- ratory events or irreversible neurocognitive impairments in survivors. When resources permit, the dynamics of restored oxygen delivery by transfusion are particularly observable in SMA, as the triggers to transfuse are so much lower (and the odds of corresponding lactic acidosis are so much higher) than in HICs. Questions on the best haemotherapy approaches to SMA remain, be these in dosage, infusion rate, component preparation or matching options; these funda- mental concerns now transcend those related to storage duration. As a persisting global scourge, SMA therefore keeps driving and facing the mandate to bank life-preserving blood for those with the most to gain (and otherwise lose). Key words: blood groups, blood safety, blood supply, immunogenetics, malaria, transfusion medicine. Introduction: A global view on how anaemia and malaria converge Malarial anaemia is an ancient scourge that remains far from eliminated. Anaemia affects 1Á93 billion people or 27% of the world, with its first and third most common causes owing to iron deficiency (63%) and malaria (4%) [1], despite these being preventable [2]. Most (89%) of the global bur- den is in the developing world, comprising ~81 million malaria-attributed anaemia cases per year, and ~3 million associated years lived with disability (YLD), the absolute and relative numbers of which are not yet decreasing [1]. Six species of Plasmodial protozoans affect humans, the most impactful of which is P. falciparum[3, 4] on account of its worldwide distribution and range of red blood cell (RBC) involvement (Table 1). These parasites are transmitted by Anopheline mosquitoes, the paired reaches of which are tropical, although these once extended as far as temperate zones in the North American Great Lakes and Northern Europe prior to 20th century eradication [5]. Today, 3Á2 billion (or 42% of the world) remain at risk of malaria, with 300 million infections (in Correspondence: Christine Cserti-Gazdewich, 200 Elizabeth Street, UHN TGH BTL 3EC-306, Toronto ON, M5G-2C4, Canada E-mail: christine.cserti@uhn.ca 1