Successful management of severe Kell alloimmunization in pregnancy with intravenous immune globulin.

Hemolytic Disease of the Fetus and Newborn (HDFN) is a condition that affects 1 to 2 out of 1000 patients during pregnancy (1). When an alloantibody is present, it is essential to identify its nature in order to organize appropriate follow-up. Kell-mediated HDFN is rare; it occurs in about 5% of Kell alloimmunized pregnant women. It is important to note that in case of anti-Kell immunization, the severity of HDFN is not correlated with maternal antibody titers, and anemia tends to occur earlier and more severely. Therefore, early diagnosing and management of this condition is crucial. In the management of severe fetal anemia due to Kell immunization, available treatments include in utero transfusion (IUT), immunoglobulin therapy. Other alternative treatments exist, such as plasmapheresis. Intravenous immunoglobulin (IVIG), a noninvasive therapeutic approach, acts through multiple mechanisms. IVIG has been evaluated in cases of RhD immunization with high maternal antibody titers and a history of pregnancies involving early hydrops or intrauterine death. Regarding the potential benefits of intravenous IgG therapy, it may delay the need for early IUT, reduce the overall reliance on IUT, and have a positive impact on obstetric outcomes. This case of IV IgG therapy of anti-Kell immunization offers a thought-provoking avenue for future exploration.

Erythropoietin downregulates red blood cell clearance, increasing transfusion efficacy in severely anemic recipients.

Red blood cells (RBC) transfusion is used to alleviate symptoms and prevent complications in anemic patients by restoring oxygen delivery to tissues. RBC transfusion efficacy, that can be measured by a rise in hemoglobin (Hb) concentration, is influenced by donor-, product-, and recipient-related characteristics. In some studies, severe pre-transfusion anemia is associated with a greater than expected Hb increment following transfusion but the biological mechanism underpinning this relationship remains poorly understood. We conducted a prospective study in critically ill patients and quantified Hb increment following one RBC transfusion. In a murine model, we investigated the possibility that, in conjunction with the host erythropoietic response, the persistence of transfused donor RBC is improved to maintain a highest RBC biomass. We confirmed a correlation between a greater Hb increment and a deeper pre-transfusion anemia in a cohort of 17 patients. In the mouse model, Hb increment and post-transfusion recovery were increased in anemic recipients. Post-transfusion RBC recovery was improved in hypoxic mice or those receiving an erythropoiesis-stimulating agent and decreased in those treated with erythropoietin (EPO)-neutralizing antibodies, suggesting that EPO signaling is necessary to observe this effect. Irradiated recipients also showed decreased post-transfusion RBC recovery. The EPO-induced post-transfusion RBC recovery improvement was abrogated in irradiated or in macrophage-depleted recipients, but maintained in splenectomized recipients, suggesting a mechanism requiring erythroid progenitors and macrophages, but which is not spleen-specific. Our study highlights a physiological role of EPO in downregulating post-transfusion RBC clearance, contributing to maintain a vital RBC biomass to rapidly cope with hypoxemia.

Fat emboli and critical illness-associated cerebral microbleeds (CICMs) in a patient with sickle cell disease: Do these 2 entities coexist?

We report the case of a 30-year-old female patient with sickle cell disease presenting with an acute chest syndrome and neurological deterioration. Cerebral magnetic resonance imaging revealed a handful of foci of diffusion restriction and numerous microbleeds with marked involvement of corpus callosum and subcortical white matter, with relative sparing of the cortex and deep white matter. Corpus callosum-predominant and juxtacortical microbleeds have been typically documented in cerebral fat embolism syndrome, but also in the so-called "critical-illness-associated cerebral microbleeds", a recently described entity associated with respiratory failure. We discussed whether these 2 entities may coexist.

An Unusual Case of Delayed Hemolytic Transfusion Reaction With Hyperhemolysis Syndrome Due to Anti-Jkb and Anti-Fya Alloantibodies.

Delayed hemolytic transfusion reaction (DHTR) is a complication appearing a few days to weeks due to alloimmunization following packed red blood cells (RBCs) transfusion, a pregnancy, or transplantation. Hyperhemolysis syndrome (HS) is a severe form of DHTR defined by a drop of hemoglobin to a level lower than before the transfusion, reflecting a destruction of the patient's own RBCs not presenting the targeted antigen as well as the transfused RBCs. Usually seen in sickle cell disease (SCD) patients, HS remains very rare in patients without a hematologic disorder. We report the case of an 82-year-old Caucasian woman who presented with a DHTR with HS after being transfused packed RBC twice in the context of rectal bleeding. The patient was not known for any hemoglobinopathy and did not have a history of massive transfusions nor multiple pregnancies putting her at risk of alloimmunization. Our patient developed anti-C, anti-Fya and anti-Jkb antibodies, known to be harmful antibodies. First line of treatment after avoidance of further transfusions is intravenous immunoglobulins for 3 to 5 days and high-dose corticosteroids. Exceptional in the non-SCD population, this complication should be recalled by clinicians as it can be fatal if not treated appropriately. We performed a review of the literature using the words "delayed hemolytic transfusion reaction" and "hyperhemolysis syndrome" for similar cases. Finally, we describe how to diagnose, manage, and prevent this potentially fatal complication, which is still underrecognized even within the SCD population.

Rapid clearance of storage-induced microerythrocytes alters transfusion recovery.

Permanent availability of red blood cells (RBCs) for transfusion depends on refrigerated storage, during which morphologically altered RBCs accumulate. Among these, a subpopulation of small RBCs, comprising type III echinocytes, spheroechinocytes, and spherocytes and defined as storage-induced microerythrocytes (SMEs), could be rapidly cleared from circulation posttransfusion. We quantified the proportion of SMEs in RBC concentrates from healthy human volunteers and assessed correlation with transfusion recovery, investigated the fate of SMEs upon perfusion through human spleen ex vivo, and explored where and how SMEs are cleared in a mouse model of blood storage and transfusion. In healthy human volunteers, high proportion of SMEs in long-stored RBC concentrates correlated with poor transfusion recovery. When perfused through human spleen, 15% and 61% of long-stored RBCs and SMEs were cleared in 70 minutes, respectively. High initial proportion of SMEs also correlated with high retention of RBCs by perfused human spleen. In the mouse model, SMEs accumulated during storage. Transfusion of long-stored RBCs resulted in reduced posttransfusion recovery, mostly due to SME clearance. After transfusion in mice, long-stored RBCs accumulated predominantly in spleen and were ingested mainly by splenic and hepatic macrophages. In macrophage-depleted mice, splenic accumulation and SME clearance were delayed, and transfusion recovery was improved. In healthy hosts, SMEs were cleared predominantly by macrophages in spleen and liver. When this well-demarcated subpopulation of altered RBCs was abundant in RBC concentrates, transfusion recovery was diminished. SME quantification has the potential to improve blood product quality assessment. This trial was registered at www.clinicaltrials.gov as #NCT02889133.