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Sickle Cell Disease
Published in Vincenzo Berghella, Maternal-Fetal Evidence Based Guidelines, 2022
An abnormal variant of hemoglobin is HbS, which occurs because of a single nucleotide mutation in which valine is substituted for glutamic acid at position 6 (E6V substitution). This substitution replaces a hydrophobic amino acid in place of a hydrophilic amino acid in the β-globin gene. This mutation does not change the morphology of hemoglobin under normal oxygen concentration, but allows HbS to polymerize when in conditions of low oxygen concentration. This polymerization triggers a cascade of repeated injury to the red-cell membrane, which causes the red blood cell to assume a characteristic sickle shape. The sickled red blood cells are brittle, causing increased hemolysis and difficulty passing through small capillaries, leading to vessel occlusion and ischemia. This tissue ischemia leads to acute and chronic pain, as well as to end-organ damage. As vaso-occlusion can occur in any vessel, this is a systemic disease that can affect multiple organs. The life span of a sickle cell is about 10–20 days compared to the 120 days life span of a normal red blood cell. This chronic hemolysis contributes to the anemia [1, 5, 6]. Dehydration, infection, decrease in oxygen tension, and acidosis, are common triggers of cell sickling and sickle cell crisis. Sickle cell crisis is a term used to label several different and independent acute conditions occurring in patients with sickle cell disease (vaso-occlusive crisis, aplastic crisis, hemolytic crisis).
Sickle cell disease
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
Marc R. Parrish, John C. Morrison
The occurrence of a vaso-occlusive crisis during labor offers additional challenges to the provider. Obviously, with painful uterine contractions, the diagnosis of a vaso-occlusive crisis may be more difficult. If delivery is expected within a short time, a simple transfusion of two units of leukocyte-reduced washed red cells can be considered. During labor, patients should remain in the lateral recumbent position and receive oxygen by tight-fitting face mask. Careful monitoring of maternal and fetal vital signs is essential. Usually, when crisis has been diagnosed during labor and late decelerations appear, infusion of blood products has been associated with resolution of suspected fetal hypoxemia. Maternal blood gas assessment, if necessary, is carried out, but invasive hemodynamic monitoring is avoided unless other concomitant disease processes such as preeclampsia, and so on, are present. Urinary catheters, as well as intrauterine catheters, are discouraged, because of their association with increased infection.
Rheology of the Hemolytic Anemias
Published in Gordon D. O. Lowe, Clinical Blood Rheology, 2019
The anemia of homozygous sickle cell disease (SS) is Theologically advantageous in that the viscosity of oxygenated blood, because of the low hematocrit, is approximately normal. This may provide some protection against large vessel occlusion, which as been described only occasionally.129 Capillary occlusion is usually considered to be the cause of tissue ischemia at the onset of a painful, vaso-occlusive crisis130 but whether this is caused by sickle cells obstructing the entrance to narrow capillaries, or whether impedance of blood flow starts in the postcapillary venules, because of the low oxygen tension, is not clear. A recent study, using laser Doppler velocimetry, has shown evidence of oscillatory flow in the microcirculation of the skin in the asymptomatic phase of sickle cell disease, demonstrating the potential importance of vasomotor activity in the terminal arterioles and precapillary sphincter region.131 Apart from uncertainty over the site of initial stasis, it is also uncertain whether capillary occlusion is caused by irreversibly sickled cells (ISC), which comprise a minority (1 to 30%) of circulating erythrocytes, or by the larger reversibly sickled cell (RSC) population.
Contributions of von Willebrand factor to clinical severity of sickle cell disease: a systematic review and metanalysis
Published in Hematology, 2022
T. U. Nwagha, Martins Nweke, E. D. Ezigbo
Sickle cell disease (SCD) is a group of autosomal recessive disorders characterized by phenotypic variations [1]. Two copies of a mutant -globin allele or an allele that specifies a deficient or faulty -globin allele cause SCD [2]. As a result, erythrocytes are rigid with increased expression of adhesion molecules. They adhere and occlude vessels, leading to ischemia/reperfusion injury with oxidative stress and damage-induced cell lysis [3]. These pathogenic mechanisms explain clinical symptoms such as chronic hemolytic anemia seen in sickle cell anemia, a subtype of SCD, and episodic vaso-occlusive crisis. Individuals with elevated hemolytic rates run the risk of developing a syndrome characterized by leg ulcers, pulmonary hypertension, priapism, and its resultant side effect of sexual dysfunction [4].
Clinical Features and Outcome of Sickle Cell Disease in a Tertiary Center in Northern Lebanon: A Retrospective Cohort Study in a Local, Hospital-Associated Registry
Published in Hemoglobin, 2021
Adlette Inati, Chadi Al Alam, Cristel El Ojaimi, Taghrid Hamad, Hemanth Kanakamedala, Virginia Pilipovic, Ramzieh Sabah
Sickle cell disease, a multi-system disorder caused by a single gene mutation, is characterized by hemolytic anemia, vaso-occlusion, endothelial dysfunction, organ failure, and significant lifetime morbidity and early mortality [1,2]. Sickle cell disease is a disorder of global importance with both economic and clinical significance [1]. Many children with sickle cell disease, specifically those born in underdeveloped countries, die undiagnosed or in early childhood from sepsis and/or acute splenic sequestration (ASS) due to a lack of access to medical care [3]. Others may die later from disease complications, including stroke, acute chest syndrome (ACS), and end-organ failure or from the consequences of under-recognized chronic iron overload resulting from blood transfusions [4]. Recurrent episodes of vaso-occlusive crisis (VOC), the clinical hallmark of sickle cell disease, are unpredictable and extremely painful events that can lead to serious acute and chronic complications and repeated inpatient hospitalization [5–8].
Refractory acquired thrombotic thrombocytopenic purpura in a patient with sickle cell trait successfully treated with caplacizumab
Published in Hematology, 2021
Vibhuti Aggarwal, Zachary Singer, Donna Ledingham, Ibraheem Othman
TTP can present similarly to a sickle cell crisis complicated by vaso-occlusion and multiorgan injury. A sickle cell vaso-occlusive crisis is commonly associated with pain in the back, legs, knees, arms, chest, or abdomen, often presenting bilaterally and with similar patterns in recurrent episodes [19]. In contrast, initial symptoms of TTP may include fatigue, dyspnea, petechiae, weakness, abdominal pain, or nausea and vomiting and is less likely to present with bony pain [20]. Treatment of multiorgan injury in the setting of a sickle cell vaso-occlusive crisis is incompletely understood. Small studies have supported the use of red blood cell transfusion for acute multiorgan injury; however, the optimal type (simple or exchange) and duration of transfusion are unknown [21]. TTP, however, requires immediate initiation of PEX to reduce morbidity and mortality, with adjunctive therapies such as glucocorticoids, rituximab and caplacizumab.