TAILIEUCHUNG - Chapter 099. Disorders of Hemoglobin (Part 5)

Sickle Cell Syndromes The sickle cell syndromes are caused by a mutation in the β-globin gene that changes the sixth amino acid from glutamic acid to valine. HbS (α2β26 Glu→Va1) polymerizes reversibly when deoxygenated to form a gelatinous network of fibrous polymers that stiffen the RBC membrane, increase viscosity, and cause dehydration due to potassium leakage and calcium influx (Fig. 99-3). These changes also produce the sickle shape. Sickled cells lose the pliability needed to traverse small capillaries. They possess altered sticky membranes (especially reticulocytes) that are abnormally adherent to the endothelium of small venules. These abnormalities provoke unpredictable. | Chapter 099. Disorders of Hemoglobin Part 5 Sickle Cell Syndromes The sickle cell syndromes are caused by a mutation in the 0-globin gene that changes the sixth amino acid from glutamic acid to valine. HbS a2026 Glu Val polymerizes reversibly when deoxygenated to form a gelatinous network of fibrous polymers that stiffen the RBC membrane increase viscosity and cause dehydration due to potassium leakage and calcium influx Fig. 99-3 . These changes also produce the sickle shape. Sickled cells lose the pliability needed to traverse small capillaries. They possess altered sticky membranes especially reticulocytes that are abnormally adherent to the endothelium of small venules. These abnormalities provoke unpredictable episodes of microvascular vasoocclusion and premature RBC destruction hemolytic anemia . Hemolysis occurs because the spleen destroys the abnormal RBC. The rigid adherent cells also clog small capillaries and venules causing tissue ischemia acute pain and gradual end-organ damage. This venoocclusive component usually dominates the clinical course. Prominent manifestations include episodes of ischemic pain . painful crises and ischemic malfunction or frank infarction in the spleen central nervous system bones liver kidneys and lungs Fig. 99-3 . Figure 99-3 Pathophysiology of sickle cell crisis. Several sickle syndromes occur as the result of inheritance of HbS from one parent and another hemoglobinopathy such as 0 thalassemia or HbC a2026 Glu- Lys from the other parent. The prototype disease sickle cell anemia is the homozygous state for HbS Table 99-2 . Table 99-2 Clinical Features of Sickle Hemoglobinopathies Conditio n Clinical Abnormalities Hemoglo bin Level g L g dL MC V fL Hemoglo bin Electrophoresis Sickle cell trait None rare painless hematuria Normal Nor mal Hb S A 40 60 Sickle cell anemia Vasoocclu sive crises with infarction of spleen brain 70-100 7-10 80- 100 Hb S A 100 0 Hb F .

• Y học thường thức
• Disorders of Hemoglobin
• bệnh học và điều trị
• bài giảng bệnh học
• tài liệu học ngành y
• Harrisons Internal Medicine
• BMC Musculoskeletal Disorders
• Intertrochanteric fractures
• Unstable fractures
• Hemoglobin drop
• Perioperative complications
• AO classification
• medical books
• pharmacology
• epidemiologic
• Obstetrics
• anatomy
• Preventing Morbidity
• Multidisciplinary Care
• Total knee arthroplasty
• Sedative hypnotics
• Post operative complications
• Orthopaedic surgery
• Locomotive syndrome risk
• Musculoskeletal organs
• Glycated hemoglobin
• Total protein
• Tranexamic acid
• Intravenous injection
• Topical injection
• Articular cartilage
• Synovial cells
• Thrombospondin motifs
• Aggrecan degradation
• Early stage osteoarthritis