Sickle Cell Disease:
Clinical:
Sickle cell anemia affects 0.15% of the African-American population. It is a genetic disorder in which the amino acid valine is substituted for glutamic acid in the sixth position of the beta chain of hemoglobin. This amino acid substitution causes the red blood cells to "sickle" and elongate when deoxygenated- this decreases their pliability in the microciculation with resultant capillary obstruction, tissue ischemia, and infarction. Intrathoracic manifestations include:Pneumonia: Patients with sickle cell disease are 100 times more susceptible to pneumonia than the general population. Encapsulated organisms such as S. pneumoniae and H. influenzae are most common.
Hyperkinetic circulation: The underlying severe anemia is associated with a hyperkinetic physiology with recruitment of all pulmonary vessels. The resultant high cardiac output will favor myocardial dilatation and hypertrophy. Chest radiographs demonstrate multichamber cardiomegaly with equalization or cephalization of pulmonary blood flow. The perfusion pattern can mimick a left-to-right shunt, however, the vascular pedicle will be widened due to the increased blood volume.
H-shaped vertebrae: Microvascular occlusion results in infarction of the vertebral end-plates which produces a "step-off" deformity that produces an "H-shaped" appearance to the vertebra. The finding may be seen in only about 10% of sickle cell patients, but is felt to be pathognomonic [1].
Extramedullary hematopoiesis: Extramedullary hematopoiesis
appears
as unilateral or bilateral, smooth, sharply marginated paraspinal
and paracostal
masses without ersion of the vertebral bodies.
Gastrointestinal vaso-occlusive crisis: Vaso-occlusive episodes
of abdominal pain are attributed to microvascular occlusion of the
post capillary venules leading to infarcts in the mesentery and
abdominal viscera [2]. CT imaging will demonstrate segmental of
diffuse bowel wall thickening [2].
REFERENCES:
(1) J Thorac Imaging 1998; Leong CS, et al.
Thoracic manifestations of sickle cell disease. 13: 128-134
(2) AJR 2015; Gardner CS, Jaffe TA. CT of gastrointestinal
vasoocclusive crisis complicating sickle cell disease. 204:
994-999
