Clinical Manifestations and Treatment. A child with sickle cell anemia is vulnerable to life-threatening infection by 4 months of age. By that time, splenic dysfunction is caused by sickling of the RBCs within the spleen, resulting in an inability to filter microorganisms from the bloodstream in most patients. Splenic dysfunction is followed, eventually, by splenic infarction, usually by 2 to 4 years of age. The loss of normal splenic function makes the patient susceptible to overwhelming infection by encapsulated organisms, especially Streptococcus pneumoniae and other pathogens (Table 150-8).The hallmark of infection is fever. A febrile patient with a sickle cell syndrome (temperature >38.5°C) must be evaluated immediately (see Chapter 96). Current precautions to prevent infections include prophylactic daily oral penicillin begun at diagnosis and vaccinations against pneumococcus, Haemophilus influenzae type b, hepatitis B virus, and influenza virus.
The anemia of hemoglobin SS disease is usually a chronic, moderately severe, hemolytic anemia that is not routinely transfusion dependent. The severity depends in part on the patient’s phenotype. Manifestations of chronic anemia include jaundice, pallor, variable splenomegaly in infancy, a cardiac flow murmur, and delayed growth and sexual maturation. Decisions about transfusion should be made on the basis of the patient’s clinical condition, the hemoglobin level, and the reticulocyte count.
Sickle cell disease is complicated by sudden, occasionally severe and life-threatening events caused by the acute intra-vascular sickling of the RBCs, with resultant pain or organ dysfunction (so-called crisis). In two different clinical situations, an acute, potentially life-threatening decline in the hemoglobin level may be superimposed on the chronic compensated anemia. Splenic sequestration crisis is a life-threatening, hyperacute drop in the hemoglobin level (blood volume) secondary to splenic pooling of the patient’s RBCs and sickling within the spleen. The spleen is moderately to markedly enlarged, and the reticulocyte count is elevated. In an aplastic crisis, parvovirus B19 infects RBC precursors in the bone marrow and induces transient RBC aplasia with reticulocytopenia and a rapid worsening of anemia because of the very short life span of sickle RBCs. Simple transfusion therapy is indicated for sequestration and aplastic crises when the anemia is symptomatic.
Vasoocclusive painful events may occur in any organ of the body and are manifested by pain and/or significant dysfunction (see Table 150-8). The acute chest syndrome is a vasoocclusive crisis within the lungs with evidence of a new infiltrate on chest radiograph. It is often associated with infection and infarction. The patient may first complain of chest pain but within a few hours develops cough, increasing respiratory and heart rates, hypoxia, and progressive respiratory distress. Physical examination reveals areas of decreased breath sounds and dullness on chest percussion. Treatment involves early recognition and prevention of arterial hypoxemia. Oxygen, fluids, judicious use of analgesic medications, antibiotics, bronchodilators, and RBC transfusion (rarely exchange transfusion) are indicated in therapy for acute chest syndrome. Incentive spirometry may help reduce the incidence of acute chest crisis in patients presenting with pain in the chest or abdomen.