Anemia de celulas falciformes

AFIP ARCHIVES

971

From the Archives of the AFIP
Sickle Cell Anemia1
CME FEATURE
See accompanying test at http:// www.rsna.org /education /rg_cme.html

Gael J. Lonergan, Lt Col, USAF, MC ● David B. Cline, MAJ, MC, USA Susan L. Abbondanzo, MD Sickle cell anemia (SCA) is a disease caused by production of abnormal hemoglobin, which binds with other abnormal hemoglobin molecules within thered blood cell to cause rigid deformation of the cell. This deformation impairs the ability of the cell to pass through small vascular channels; sludging and congestion of vascular beds may result, followed by tissue ischemia and infarction. Infarction is common throughout the body in the patient with SCA, and it is responsible for the earliest clinical manifestation, the acute pain crisis, whichis thought to result from marrow infarction. Over time, such insults result in medullary bone infarcts and epiphyseal osteonecrosis. In the brain, white matter and gray matter infarcts are seen, causing cognitive impairment and functional neurologic deficits. The lungs are also commonly affected, with infarcts, emboli (from marrow infarcts and fat necrosis), and a markedly increased propensity forpneumonia. The liver, spleen, and kidney may experience infarction as well. An unusual but life-threatening complication of SCA is sequestration syndrome, wherein a considerable amount of the intravascular volume is sequestered in an organ (usually the spleen), causing vascular collapse; its pathogenesis is unknown. Finally, because the red blood cells are abnormal, they are removed from thecirculation, resulting in a hemolytic anemia. For the patient with SCA, however, the ischemic complications of the disease far outweigh the anemia in clinical importance.

LEARNING OBJECTIVES FOR TEST 5
After reading this article and taking the test, the reader will be able to: Describe the pathophysiology of hemoglobin and red blood cells in sickle cell anemia. Define the imaging features of thecommon sequelae of sickle cell anemia. Describe the role of imaging in the diagnosis and evaluation of suspected complications of sickle cell anemia.

Abbreviations: ACS acute chest disease, Hb S sickle cell hemoglobin, Hb SA sickle cell hemoglobin, RBC red blood cell, SCA sickle cell anemia

heterozygous sickle cell hemoglobin, Hb SS

homozygous

Index term: Sickle cell disease (SS, SC),10.651, 40.214, 40.651, 60.651, 76.651, 77.651, 81.651 RadioGraphics 2001; 21:971–994
1From the Department of Radiology and Nuclear Medicine, Uniformed Services University of the Health Sciences, Bethesda, Md (G.J.L.); Departments of Radiologic Pathology (G.J.L.) and Hematopathology (S.L.A.), Armed Forces Institute of Pathology, 14th St and Alaska Ave NW, Bldg 54, Rm M-121, Washington, DC20306-6000; and Department of Radiology, Walter Reed Army Medical Center, Washington, DC. Received December 15, 2000; revision requested December 28 and received January 26, 2001; accepted February 7. Address correspondence to G.J.L. (e-mail: lonergan@afip.osd.mil).

The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting theviews of the Departments of the Air Force, Army, or Defense.
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RSNA, 2001

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July-August 2001

RG f Volume 21

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Number 4

Introduction
Sickle cell anemia (SCA) is a hemolytic anemia characterized by abnormally shaped (sickled) red blood cells (RBCs), which are removed from the circulation and destroyed at increased rates, leading to anemia. Of greater clinical importance,the sickled RBCs cause vascular occlusion, which leads to tissue ischemia and infarction. The underlying abnormality in the RBC of SCA is the presence of abnormal sickle cell hemoglobin (Hb S), which, when deoxygenated, becomes relatively insoluble and forms aggregates with other hemoglobin molecules within the RBC. These aggregates develop into long chains, which distort the RBC into a sickled...