[Sickle-cell disease: geographical distribution and population estimates]

Neonatal Screening for Sickle Cell Disease in Congo

INTRODUCTION

Sickle cell disease is an autosomal recessive inherited disorder due to the mutation of a gene coding for the globin beta chain. The aim of this study is to update the epidemiological data on hemoglobinoses, in particular sickle cell disease in newborns in Congo.

MATERIALS AND METHODS

This was a descriptive cross-sectional study, conducted from October 1, 2019, to March 31, 2020, throughout the Congolese national territory. It involved all full-term newborns, without distinction of nationality, aged 5 days or less, and whose parents consented to participate in the study. The blood samples, taken at the heel and collected on Whatman blotting paper, were analyzed using the HPLC Variant NBS machine.

RESULTS

In 2897 newborns (NN) screened, hemoglobin abnormalities were found in 603 NN (20.81%). The mean age of these newborns was 1 day (extremes 0 and 5 days). The male-to-female ratio was 1.03. Abnormal hemoglobins were mainly Hb S (n = 597 (97.71%)); Hb C (n = 5 (0.82%)); and variants (n = 7 (1.15%)). The national prevalence of major sickle cell (MSC) syndromes and sickle cell trait was 1.35% and 19.43%, respectively. The prevalence ranged from 1.77% to 2.56% for MSS in four departments and from 20.5% to 25.8% for the sickle cell trait in six other departments.

CONCLUSION

Data on homozygous sickle cell disease remain consistent with previous studies. However, further studies should clarify the molecular anomalies of the variants observed in our samples.

Nanoscale adhesion profiling and membrane characterisation in sickle cell disease using hybrid atomic force microscopy-IR spectroscopy

Sickle cell disease (SCD) presents a significant global health problem. At present there is no effective treatment, with most being supportive for its associated complications such as the vaso-occlusive crises that result from increased cell adhesion. Hypoxic sickle cells have previously shown greater phosphatidylserine (PS) exposure and oxidative damage, as well as being notably "stickier" suggesting that increased cell cohesion and adhesion to the blood vessel endothelium is a possible mechanism for vaso-occlusion. The present work uses the hybrid technique of atomic force microscopy nano-infrared spectroscopy (AFM-IR) to probe changes to the coefficient of friction and C-O IR intensity in SCD on a nanoscale for dried red blood cells (RBCs) fixed under conditions of hypoxia and correlates these observations with adhesive interactions at the membrane. Using functionalised AFM tips, it has been possible to probe adhesive interactions between hydrophilic and hydrophobic moieties exposed at the surface of the dried RBCs fixed under different oxygenation states and for different cell genotypes. The results are consistent with greater PS-exposure and oxidative damage in hypoxic sickle cells, as previously proposed, and also show strong correlation between localised oxidative damage and increased adhesion. A mechanistic explanation involving significant lipid tail disruption as a result of oxidative action, in combination with differing concentrations of externalised PS lipids, is proposed to explain the observed adhesion behaviour of each type of cell.

Hematologist and transplant physicians: How and where to meet for the best of sickle cell disease patients?

Despite huge progress in the fields of newborn screening, encapsulated bacterial infection prophylaxis, immunization, and supportive care in general, people suffering from sickle cell anemia still continue to have a shorter life expectancy and a poorer quality of life due to painful vaso-occlusive events and strokes during childhood, and later, cardiac, pulmonary, and renal injuries, including in Western and high-income countries. From the 2000s, allogeneic stem cell transplantation for severe sickle cell disease from a sibling donor provided the best results-overall as well as disease-free survival-never obtained for any other disease. Nevertheless, this only curative option is proposed to few patient numbers, including in Western countries with high-level medical equipment development, with discrepancies between (i) patients and family, (ii) physicians and care centers dedicated to sickle cell disease, and (iii) hematopoietic stem cell transplant teams. Due to these discrepancies and in order to provide the same quality of discussion and treatment choice for every sickle cell disease patient, we developed a National French multidisciplinary pluri-annual meeting dedicated to sickle cell disease patients and transplantation. We report here our experience of such a meeting.

Stage-dependent fate of Plasmodium falciparum-infected red blood cells in the spleen and sickle-cell trait-related protection against malaria

Background

Sickle-cell trait (HbAS) reduces falciparum malaria risk and suppresses parasitaemia. Although several candidate mechanisms have been proposed, their epidemiological, clinical and experimental correlates have not been adequately explained. To explore the basis for generally lower parasitaemias and delayed malaria episodes in children with HbAS, it is hypothesized here that their spleen-dependent removal of ring-infected red blood cells (RBCs) is more efficient than in children with normal haemoglobin A (HbAA).

Methods

The mechanical splenic retention of Plasmodium falciparum-infected RBCs from subjects with HbAS or HbAA was investigated using two physiologically relevant methods: microsphiltration and ex vivo spleen perfusion. P. falciparum-infected RBCs obtained from in vitro cultures and from patients were used in either normoxic or hypoxic conditions. The effect of sickling in ring-infected HbAS RBCs was also investigated.

Results

When a laboratory-adapted parasite strain was analysed, ring-infected HbAA RBCs were retained in microsphilters at similar or greater levels than ring-infected HbAS RBCs, under normoxic (retention rate 62.5 vs 43.8 %, P < 0.01) and hypoxic (54.0 vs 38.0 %, P = 0.11) conditions. When parasitized RBCs from Malian children were analysed, retention of ring-infected HbAA and HbAS RBCs was similar when tested either directly ex vivo (32.1 vs 28.7 %, P = 0.52) or after one re-invasion in vitro (55.9 vs 43.7 %, P = 0.30). In hypoxia, sickling of uninfected and ring-infected HbAS RBCs (8.6 vs 5.7 %, P = 0.51), and retention of ring-infected HbAA and HbAS RBCs in microsphilters (72.5 vs 68.8 %, P = 0.38) and spleens (41.2 vs 30.4 %, P = 0.11), also did not differ. Retention of HbAS and HbAA RBCs infected with mature P. falciparum stages was greater than 95 %.

Conclusions

Sickle-cell trait is not associated with higher retention or sickling of ring-infected RBCs in experimental systems reflecting the mechanical sensing of RBCs by the human spleen. As observed with HbAA RBCs, HbAS RBCs infected with mature parasites are completely retained. Because the cytoadherence of HbAS RBCs infected with mature parasites is impaired, the very efficient splenic retention of such non-adherent infected RBCs is expected to result in a slower rise of P. falciparum parasitaemia in sickle-cell trait carriers.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-016-1522-0) contains supplementary material, which is available to authorized users.

Heart valve surgery in patients with homozygous sickle cell disease: A management strategy

Background:

Patients with the homozygous sickle cell disease have increased perioperative mortality. Some indications like heart valve surgery, may justify an exchange blood transfusion to reduce the proportion of hemoglobin S (HbS) and complications.

Subjects and Methods:

We report two female cases aged 20 and 27, of African origin with homozygous sickle cell anemia who underwent heart valve surgery to treat mitral valve regurgitation. This presentation describes the perioperative considerations including anesthesia and postoperative care.

Results:

A partial exchange blood transfusion decreased HbS levels from respectively, 90% and 84%, 9% to 27% and 34%, and simultaneously treated the anemia. Neither sickling crisis nor acidosis occurred in any patient, and no special postoperative complication occurred. Average hospital stay was 10 days. Currently, the two patients remain alive and free of cardiac symptoms.

Discussion:

Although the presence of sickle cell disorders is associated with increased risk of sickling and thus vaso-occlusive complications, they should not be taken as a contraindication for heart valve surgery. Nevertheless, monitoring of certain parameters such as venous, arterial oxygen content, pH, and body temperature is mandatory for a better outcome. Furthermore, preoperative exchange transfusion has a positive influence on the outcome of surgery and on the survival of patients undergoing heart valves surgery. Avoiding intraoperative hypoxia, hypothermia, and vaso-constrictive agents, minimizing HbS levels with preoperative exchange transfusion, and ensuring a stress-free environment with the judicious use of sedatives made surgery relatively safe in these cases.