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Chapter 42 Sickle Cell Disease 605

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usually takes weeks. Therapy begins with gentle debridement to helplessness. Although some patients with SCD become addicted to
remove nonviable, superficial tissue from more vital areas. Wet-to-dry narcotics, this is uncommon and usually is the result of social influ-
dressings and DuoDerm hydrocolloid dressings facilitate devitaliza- ences rather than pain therapy. Well-adjusted patients have active
tion. When debridement is complete, zinc oxide–impregnated Unna coping strategies, family support, and support from the extended
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boots are used to promote healing. Bed rest speeds healing, and family unit common in African American society. Interventional
topical antibiotics may be required. It may be necessary to use elastic approaches should emphasize recognizing and reinforcing individual
wraps or leg elevation to control edema. Rapid healing of leg ulcers strengths; confronting pathologic behavior; and establishing coping
has been reported in patients treated with intravenous arginine butyr- skills through reinterpreting pain, diverting attention from pain, and
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ate. Oral zinc, local hyperbaric oxygen, chronic transfusion, using support systems. Attention to psychosocial concerns is vital
recombinant EPO, propionyl-L-carnitine, skin grafts, pentoxifylline, to the psychosocial well-being and integration into society of patients
and becaplermin (platelet-derived growth factor) may have therapeu- with SCD (see Chapter 90).
tic roles and should be considered in individual cases but have not
been formally tested for their effectiveness in accelerating resolution
of sickle cell–associated leg ulcers. Growth and Development
Myofascial syndromes consist of soft tissue swelling in subcutane-
ous edema that may have a peau d’orange appearance. These may be By age 2 years, children with SCD have detectable growth retardation
large or discrete lesions a few centimeters in diameter. These lesions that affects weight more than height and has no clear gender differ-
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are probably the result of dermal or subdermal vasoocclusion. Treat- ence. By adulthood, normal height is achieved, but weight remains
ment is symptomatic. lower than that of control participants. More severe growth delay is
noted in children with sickle cell anemia and sickle cell–β°-thalassemia;
Hb SC disease is associated with a less severe growth delay. Girls with
Cardiac Complications SCD have retarded sexual maturation that is greater in those with
sickle cell anemia and sickle cell–β°-thalassemia than those with Hb
+
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The chronic anemia of SCD is compensated by high cardiac output, SC disease and sickle cell–β -thalassemia ; it is associated with
which results in chronic chamber enlargement and cardiomegaly, and elevated gonadotropin levels for the stage of sexual development and
mild to moderate mitral and tricuspid regurgitation even in young delayed menarche. Boys also have delayed sexual maturation, which
children. The electrocardiogram shows evidence of left ventricular is more severe in those with sickle cell anemia than those with Hb
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hypertrophy and less often first-degree block and nonspecific ST-T SC disease. Retarded sexual maturation in boys can be attributable
wave changes. Left ventricular dilation correlates with age and to primary hypogonadism, hypopituitarism, or hypothalamic insuf-
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inversely correlates with total Hb. An age-dependent loss of cardiac ficiency. The etiology of these multiple endocrine deficiencies may
reserve may predispose to heart failure in adult patients stressed by relate to underlying sickle cell pathophysiology or iron overload and
fluid overload, transfusion, exacerbation of anemia, hypoxia, or emphasizes the importance of a comprehensive basic management
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hypertension. Cardiac function can be improved by transfusion. and disease modification approach as outlined earlier in this chapter.
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Acute myocardial infarction in the absence of coronary disease has Improved growth has been reported with HU, transfusion, folic
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been reported, and in one autopsy series, 9.7% of 72 consecutive acid supplementation, zinc supplementation, and nutritional
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patients with SCD had myocardial infarction. It appears that supplementation. When children have both SCD and hypersplen-
myocardial infarction may occur with normal coronary arteries as a ism, splenectomy may result in improved protein turnover, metabolic
result of increased oxygen demand exceeding limited oxygen-carrying rate, and growth parameters. 244
capacity or as a result of microcirculatory impairment. As mentioned
earlier, pulmonary hypertension (>30 mm Hg) is a relatively common
finding in patients with SCD and can be associated with right ven- VARIANT SICKLE CELL SYNDROMES
tricular hypertrophy. It has been suggested that the increased rate of
sudden death observed in SCD may be related to cardiac autonomic The sickle cell syndromes that result from inheritance of the sickle
dysfunction, as detected by abnormal heart rate variability in response cell gene in simple heterozygosity or in compound heterozygosity
to selected postural maneuvers. 236 with other mutant β-globin genes are sickle cell trait, Hb SC disease,
and sickle cell–β-thalassemia. These and other less common com-
pound heterozygosity syndromes are reviewed.
Multiorgan Failure
This disastrous acute event involves multiple organ systems, includ- Sickle Cell Trait
ing the lungs, brain, kidneys, liver, hematologic system, and heart,
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and usually leads to death. It may be precipitated by infection, The prevalence of sickle cell trait is approximately 8% to 10% in
vasoocclusion, or fat embolus and consists of a constellation of life- African Americans and as high as 25% to 30% in certain areas of
4
threatening processes, including hypoxemia, acidosis, inflammation, western Africa. Approximately 2.5 million people in the United
vascular permeability, severe anemia, disseminated intravascular States and 30 million in the world are heterozygous for the sickle
coagulation, renal failure, and hepatic failure. In addition to therapy cell gene. Sickle cell trait is largely a benign carrier condition with
specific for these processes, exchange transfusion, plasma infusion or no obvious laboratory hematologic manifestations under basal condi-
exchange, and corticosteroids should be considered. tions: RBC morphology, RBC indices, and the reticulocyte count
are normal, and ISCs are not seen on the peripheral blood smear.
The usual partition of Hb A and Hb S in sickle cell trait is 60 : 40
Psychosocial Issues owing to a greater posttranslational affinity of α chains for β than
A
6
S
for β chains. When α-thalassemia is coinherited with sickle cell
Modern insights into the psychosocial adjustment of patients with trait, the preferential affinity results in a decreased percentage of
SCD have provided a level of understanding that allows interventional Hb S relative to the number of α-globin genes deleted (i.e., αα/αα
therapy. Although most patients with SCD are generally well 40% Hb S; −α/αα 35% Hb S; −α/−α 29% Hb S; −−/−α 21%
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adjusted, there are risks of depression, low self-esteem, social isola- Hb S). 133
tion, poor family relationships, and withdrawal from normal daily There are a few clinical complications of sickle cell trait; splenic
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living. Particular stressors are recurrent and unpredictable pain and infarction occurs at high altitude. It is a cause of hematuria and
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the response to it, curtailed activity because of pain, misinterpretation hyposthenuria. The frequency of urinary tract infection may be
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of the meaning of pain, and depression leading to learned increased. There is an association with renal medullary carcinoma.