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sickle_cell

sickle cell disease (SCD)

introduction

  • sickle cell disease is a hereditary autosomal dominant haemoglobinopathy due to homozygous HbS which usually presents in childhood
  • the gene is present in 8% (2 million) of black Americans who thus have sickle cell trait but only 30,000 have homozygous HbS, thus sickle cell disease occurs in 1 in 500 African Americans
  • sickle cell trait is high in parts of Africa (reaching 30% is some areas) and other regions where malaria is endemic (Sicily, Greece, southern Turkey, and India) as sickle cell trait offers survival benefit in malaria prone regions.

clinical features

  • painful vaso-occlusive crises
    • the most common and most distinguishing clinical manifestation of SCD
    • triggered by:
      • hypoxia
      • dehydration and acidosis
      • changes in body temperature
  • acute and chronic pain in any body part due to infarctions
    • bone pain from infarction of marrow
    • hand-foot syndrome
      • dactylitis presenting as bilateral painful and swollen hands and/or feet in children
    • avascular necrosis of the femoral or humeral head
    • chronic leg ulcers
  • chronic, haemolytic anaemia
  • functional hyposplenism
    • high risk of invasive pneumococcal disease and infections by other encapsulated bacteria
    • dult infections are predominately with gram-negative organisms, especially Salmonella
  • aplastic crisis
    • serious complication due to infection with B19V
  • splenic sequestration
    • onset of life-threatening anemia with rapid enlargement of the spleen and high reticulocyte count
  • growth retardation, delayed sexual maturation, being underweight
  • acute chest syndrome:
    • young children present with chest pain, fever, cough, tachypnea, leukocytosis, and pulmonary infiltrates in the upper lobes
    • adults are usually afebrile, SOB with severe chest pain, with multilobar/lower lobe disease
  • pulmonary hypertension
  • eye: ptosis, retinal vascular changes, proliferative retinitis
  • urologic:
    • kidneys lose concentrating capacity
      • median age at the time of renal failure in patients with SCD is 23 years
      • median survival time after the diagnosis of ESRD is about 4 years
      • median age of death is 27 years, despite dialysis treatment
    • priapism is a well-recognized complication
sickle_cell.txt · Last modified: 2013/06/07 01:32 by gary1