Clinical biomarkers in sickle cell disease

Sickle cell disease (SCD) is a hereditary blood disorder caused by a single gene. Various blood and urine biomarkers have been identified in SCD which are associated with laboratory and medical history. Biomarkers have been proven helpful in identifying different interconnected disease-causing mechanisms of SCD, including hypercoagulability, hemolysis, inflammation, oxidative stress, vasculopathy, reperfusion injury and reduced vasodilatory responses in endothelium, to name just a few. However, there exists a need to establish a panel of validated blood and urine biomarkers in SCD. This paper reviews the current contribution of biochemical markers associated with clinical manifestation and identification of sub-phenotypes in SCD.     

Nutrition and sickle cell disease

A common observation in sickle cell disease is growth retardation, in particular, wasting. Wasting is associated with increased hospitalization and possibly poorer clinical outcomes. Therefore understanding the mechanism of wasting is crucial and reducing the degree of wasting by improving the nutritional status, holds the potential for modifying the course of the disease.     

Red blood cell lactate transport in sickle disease and sickle cell trait.

This study determined and compared rates and mechanisms of lactate transport in red blood cells (RBCs) of persons with 1) sickle cell disease (HbSS), 2) sickle cell trait (HbAS), and 3) a control group (HbAA). Blood samples were drawn from 30 African-American volunteers (10 HbSS, 10 HbAS, 10 HbAA). Lactate influx into RBCs was measured by using [14C]lactate at six (2, 5, 10, 15, 25, and 40 mM) unlabeled lactate concentrations. The monocarboxylate transporter pathway was blocked by p-chloromercuriphenylsulfonic acid to determine its percent contribution to total lactate influx. Generally, total lactate influx into RBCs from the HbSS group was significantly greater than influx into RBCs from HbAS or HbAA, with no difference between HbAS and HbAA. Faster influx into HbSS RBCs was attributed to increased monocarboxylate transporter activity [increased apparent Vmax (V'max)]. V'max (4.7 +/- 0.6 micromol x ml(-1) x min(-1)) for HbSS RBCs was significantly greater than V'max of HbAS RBCs (2.9 +/- 1.5 micromol x ml(-1) x min(-1)) and HbAA RBCs (2.0 +/- 0.5 micromol x ml(-1) x min(-1)). Km (42.8 +/- 8 mM) for HbSS RBCs was significantly greater than Km (27 +/- 12 mM) for HbAA RBCs. We suspect that elevated erythropoietin levels in response to chronic anemia and/or pharmacological treatment (erythropoietin injections, hydroxyurea ingestion) is the underlying mechanism for increased lactate transport capacity in HbSS RBCs.     

Brill-Zinsser disease: report of a case in Canada

This report documents the occurrence of Brill-Zinsser disease in a 48-year-old woman who experienced typhus fever in a German concentration camp. This is the first report of a case of recrudescent typhus in a European immigrating to Canada following World War II. The last reported case of Brill-Zinsser disease in Canada occurred in 1953.     

Cutaneous relapse in Hodgkin's disease: a case report

BACKGROUND: Skin involvement in Hodgkin's disease is rare, can be seen in advanced stages of the disease and indicates a poor prognosis. CASE: A young male presented with multiple nodular lesions on the chest wall and matted cervical lymph nodes. Aspiration smears from skin lesions showed atypical mononuclear cells with a prominent nucleolus, many lymphocytes and plasma cells. Smears from the lymph nodes showed classical Reed-Sternberg cells in a polymorphous background. The cytologic diagnosis of Hodgkin's lymphoma was entertained and later confirmed on skin biopsy. Past history revealed that the patient had been diagnosed with Hodgkin's disease and treated for it 2 years earlier, but had been lost to follow-up during treatment. CONCLUSION: Cutaneous Hodgkin's disease should always be considered in smears from skin lesions showing atypical mononuclear cells in a polymorphous background, even in the absence of a definitive clinical diagnosis at the time of presentation.     

Erythrocyte membrane abnormalities in sickle cell disease

A large fraction of circulating sickle red cells contain one or more large vesicles which are not found in normal erythrocytes. These vesicles contain very high levels of Ca2+, and probably account for the long-known elevation of cellular Ca2+ in sickle cells. These vesicles contain the plasma membrane CaATPase and leak Ca2+ by a nitrendipine-sensitive pathway. The question of whether an abnormal endocytic process occurs in sickle cells which could give rise to these vesicles was examined using the nonspecific endocytic marker Lucifer yellow (LY). The kinetics of formation of LY-labeled endocytic vesicles in sickle cells includes a slow component which is not found in normal (or sickle) reticulocytes. In addition, the number of sickle cells in which endocytosis can be demonstrated with this nonspecific marker consistently exceeds the number which can be labeled with markers of the receptor-mediated endocytic process. The results suggest that a slow, abnormal endocytosis takes place in sickle cells which may be the source of the Ca2(+)-containing vesicles, and therefore of the elevated Ca2+ levels characteristic of the circulating cells in this disease.     

Hypercoagulability in sickle cell disease and beta-thalassemia

Sickle cell disease (SCD) and beta-thalassemia (also referred to as beta-thalassemia) are common hereditary hemoglobinopathies with differing pathophysiologies and clinical courses. However, patients with both diseases exhibit increased platelet and coagulation activation, as well as decreased levels of natural anticoagulant proteins. In addition, they are characterized by thrombotic complications that may share a similar pathogenesis. The pathogenesis of hypercoagulability is likely multifactorial, with contributions from the abnormal red blood cell (RBC) phospholipid membrane asymmetry, ischemia-reperfusion injury, and chronic hemolysis with resultant nitric oxide depletion. More studies are needed to better define the contribution of hemostatic activation to the pathophysiology of SCD and beta-thalassemia. Furthermore, adequately controlled studies using anticoagulants and antiplatelet agents are warranted to define the role of hypercoagulability in specific complications of these diseases.     

Erythrocyte aging in sickle cell disease.

Physiological removal of old erythrocytes from the circulation by macrophages is initiated by binding of autologous IgG to senescent cell antigen (SCA). SCA is generated from the anion exchanger band 3. This process is accompanied by a number of alterations in the function and structure of band 3. We measured these aging-related parameters in erythrocytes from individuals with sickle cell anemia. Most sickle erythrocytes have characteristics that are also found in senescent normal erythrocytes, such as an increased density and considerable concentrations of cell-bound IgG. Together with the concomitant changes in structure and function of band 3, these data suggest that most sickle erythrocytes have undergone a process of accelerated aging. Preliminary results indicate that this process is reversed upon vitamin E supplementation. These data show that the erythrocyte aging paradigm may provide a useful conceptual framework for the study of the pathophysiology and the evalution of therapeutic intervention in sickle cell disease, and support the view that oxidation can generate neoantigens that are recognized by autoantibodies.     

Autonomic nervous system dysfunction: Implication in sickle cell disease

Sickle cell disease is an inherited hemoglobinopathy caused by a single amino acid substitution in the β chain of hemoglobin that causes the hemoglobin to polymerize in the deoxy state. The resulting rigid, sickle-shaped red cells obstruct blood flow causing hemolytic anemia, tissue damage, and premature death. Hemolysis is continual. However, acute exacerbations of sickling called vaso-occlusive crises (VOC) resulting in severe pain occur, often requiring hospitalization. Blood rheology, adhesion of cellular elements of blood to vascular endothelium, inflammation, and activation of coagulation decrease microvascular flow and increase likelihood of VOC. What triggers the transition from steady state to VOC is unknown. This review discusses the interaction of blood rheological factors and the role that autonomic nervous system (ANS) induced vasoconstriction may have in triggering crisis as well as the mechanism of ANS dysfunction in SCD.     

Metastatic balloon cell melanoma: a case report

BACKGROUND: The protean morphology of malignant melanoma is diagnostically challenging. Balloon cell melanoma is a histologic variant composed predominantly or entirely of large cells with abundant, vacuolated cytoplasm. It shares the cytologic features of the other subcategories of malignant melanoma, such as discohesion, nuclear pleomorphism and intranuclear cytoplasmic pseudoinclusions, but generally lacks melanin pigment and, as the name would suggest, is characterized by the presence of numerous cytoplasmic vacuoles. CASE: A 55-year-old man presented with an enlarged right cervical lymph node. Clinically and radiographically this mass was considered to be metastatic; however, the patient had no known primary neoplasm. Fine needle aspiration biopsy (FNAB) and cytologic examination showed numerous discohesive, variably sized, malignant cells with abundant, vacuolated cytoplasm and pleomorphic nuclei with irregular nuclear contours, macronucleoli and frequent intranuclear cytoplasmic pseudoinclusions. Pigment was not identified. These features, along with strong immunohistochemical positivity for S-100, HMB-45 and Melan-A, suggested the diagnosis of balloon cell melanoma. A right parotidectomy and lymph node dissection were performed, and histologic tissue evaluation confirmed the diagnosis. CONCLUSION: This case of lymph node balloon cell melanoma metastasis was diagnosed by FNAB.     

Gene therapy for sickle cell disease: An update

Sickle cell disease (SCD) is one of the most common life-threatening monogenic diseases affecting millions of people worldwide. Allogenic hematopietic stem cell transplantation is the only known cure for the disease with high success rates, but the limited availability of matched sibling donors and the high risk of transplantation-related side effects force the scientific community to envision additional therapies. Ex vivo gene therapy through globin gene addition has been investigated extensively and is currently being tested in clinical trials that have begun reporting encouraging data. Recent improvements in our understanding of the molecular pathways controlling mammalian erythropoiesis and globin switching offer new and exciting therapeutic options. Rapid and substantial advances in genome engineering tools, particularly CRISPR/Cas9, have raised the possibility of genetic correction in induced pluripotent stem cells as well as patient-derived hematopoietic stem and progenitor cells. However, these techniques are still in their infancy, and safety/efficacy issues remain that must be addressed before translating these promising techniques into clinical practice.     

Linus Pauling and sickle cell disease

The 1949 paper by Linus Pauling et al. [Science 110 (1949) 543–548] describing the discovery of sickle cell anemia as the first molecular disease had a major impact on biology and medicine. Inspired by the scholarly works of John Edsall on the history of hemoglobin research, I present a brief retrospective analysis of Pauling's paper. This is followed by some personal recollections of Edsall and Pauling.