Page 2490 - Hematology_ Basic Principles and Practice ( PDFDrive )

2222 Part XIII Consultative Hematology

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radiographic features are present. Other rare manifestations of HSP system thrombi may result. To prevent these complications, the
include neurologic, cardiac, and pulmonary events. hematocrit level should be maintained around 60% through the use
Anemia occasionally develops as a result of gastrointestinal (GI) of exchange transfusions. Small aliquots of the patient’s blood are
tract blood loss or decreased RBC production caused by renal failure. slowly removed and replaced by equal volumes of plasma or 5%
The leukocyte count is normal. Despite the impressive purpura, the albumin. Care should be taken to remove blood slowly because vas-
platelet count is normal or increased with normal platelet function. cular collapse, cyanosis, stroke, and seizures have been reported with
Coagulation factor levels usually are normal, although transient too rapid an exchange. Apheresis (erythrocytapheresis) also has been
decreases in factor XIII activity and vitamin K deficiency from severe shown to be an effective means of decreasing viscosity in patients with
vasculitis-induced intestinal malabsorption have been reported. Signs polycythemia.
of increased fibrinolysis, as evidenced by elevation of D-dimer and Infants with CCHD are at risk of developing iron-deficiency
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other markers, have been described. Bleeding in the GI tract; the anemia. The deficiency may result from the combination of poor iron
lungs; or, rarely, the central nervous system is caused by a necrotizing stores at birth (especially in premature infants), increased iron needed
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vasculitis and not a hemostatic defect. Hypercoagulability does not for enhanced erythropoiesis, poor iron intake because of poor feeding,
play a role with normal frequency of MTHFR, prothrombin, and and ongoing iron losses as a consequence of phlebotomy or exchange
factor V Leiden gene mutations. 140 transfusion. These children may exhibit symptoms of iron deficiency
HSP is considered an IgA-mediated inflammation of small vessels. (irritability, anorexia, poor weight gain) or worsening cyanosis. The
Biopsy of skin or other involved tissue reveals a leukocytoclastic hemoglobin may be normal for age but inappropriately low for the
vasculitis. Immune complexes of IgA with complement, IgG, or IgM degree of hypoxemia. Low RBC indices and hypochromic, microcytic
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have been found circulating in the serum and deposited in blood RBCs are the best indices of iron deficiency in this setting. Children
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vessel walls of the kidneys and in intestinal and skin lesions. The with polycythemia who have iron-deficiency anemia are at increased
mechanism of production, accumulation, and deposition of IgA risk for cerebral vein thrombosis because of the poor deformability
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immune complexes in the blood vessel is unclear. It has been sug- of the iron-deficient RBCs, which further increases blood viscosity.
gested that HSP may be a systemic form of IgA nephropathy, although To prevent this complication and to allow for maximal tissue oxy-
this is controversial. 143,144 Both disorders have identical features on genation, all infants should be fed iron-rich infant formula and
renal biopsy and are characterized by mesangial proliferation, occa- receive iron replacement therapy as needed to normalize RBC indices.
sional focal sclerosis, and crescent formation. 145 Hemolytic anemia, characterized by mechanical destruction of RBCs
Treatment is mainly supportive, although corticosteroids have and manifested by the presence of schistocytes in the peripheral blood
been found to provide symptomatic relief with severe joint, scrotal, smear, is occasionally seen after the placement of prosthetic heart
or abdominal pain. 146,147 They do not alter skin involvement or valves.
prevent renal involvement. Recent studies have suggested that Routine screening of patients with CHD has demonstrated coagu-
corticosteroids plus azathioprine, cyclosporin A, or cyclophosphamide lation abnormalities in 20% to 59% of children with acyanotic
may have a role in the management of severe renal involvement. 148–152 defects and in 40% to 50% of those with cyanotic heart disease (Table
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Rituximab has been reported to be effective in decreasing the symp- 152.3). Only 11% of children with CCHD have any clinical evi-
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toms of three patients with severe, refractory chronic HSP. The dence of bleeding preoperatively. However, children with underlying
prognosis is good for full recovery, except in children with renal hemostatic defects have a greater frequency and severity of postopera-
failure. tive bleeding. 157,158 Presurgical screening tests should include at least
a platelet count, platelet function assay (e.g., closure time), PT, and
aPTT. Further investigations may be indicated if there is a history of
CARDIOPULMONARY DISEASE bleeding or abnormal results on screening tests. Acquired von Will-
ebrand syndrome has been reported in patients with CHD and is
Congenital Heart Disease
Congenital heart disease (CHD) occurs in about 1% of live births.
Structural heart malformation usually follows predictable patterns TABLE Coagulation Abnormalities in Congenital Heart
such that six defects account for 70% of all cardiac disorders: ven- 152.3 Disease
tricular septal defect, atrial septal defect, tetralogy of Fallot, patent
ductus arteriosus, pulmonary stenosis, and aortic stenosis. Children Incidence (%)
with cardiac abnormalities may be acyanotic or cyanotic, depending Abnormality Acyanotic CHD Cyanotic CHD
on the underlying lesion. Hematologic abnormalities occur most Prolonged bleeding time 11 28
often in children with cyanotic critical congenital heart disease
(CCHD). Polycythemia is the bone marrow response to chronic Prolonged PT 20
hypoxemia in patients with CCHD. The decreased arterial oxygen Prolonged aPTT 19
content stimulates erythropoietin production, which in turn increases Thrombocytopenia 12–40 0–36
erythropoiesis. The resultant increased RBC mass increases the
oxygen-carrying capacity of the blood, resulting in improved tissue Abnormal platelet aggregation 14 38–70
oxygenation. With adequate compensation, erythropoietin levels fall Increased fibrinolysis 12 0–10
to normal, and higher RBC production is maintained. A second Abnormal clot retraction 10
compensatory mechanism is an increase in 2,3-diphosphoglycerate Low fibrinogen 16 12
(2,3-DPG) levels in the RBCs when the arterial oxygen tension is less
than 70 mmHg. The higher 2,3-DPG level causes a right shift of the Increased fibrin split products Occasionally
oxyhemoglobin curve, resulting in greater oxygen release to the Decreased factors II, V, VII, Occasionally
tissues. VIII, IX, X, XI, XII
Polycythemia in cyanotic children is beneficial up to a point. Decreased protein C 25 a
Because the relationship between the hematocrit and blood viscosity
is hyperbolic, minor increases in the hematocrit above 70% cause aPTT, Activated partial thromboplastin time; CHD, congenital heart disease;
PT, prothrombin time.
marked increases in blood viscosity. This higher viscosity results in a Data from MacDonald PD, Gibson BE, Braunlie J, et al: Protein C activity in
impaired perfusion within the microvasculature, with ultimately less severely ill newborns with congenital heart disease. J Perinatal Med 20:421,
tissue oxygen delivery. The impairment is magnified in severe poly- 1992.
cythemia (hematocrit level >75%) such that headache; irritability; Adapted from Lascari AD: Hematologic manifestations of childhood diseases,
New York, Thieme-Stratton, 1984, with permission.
dyspnea; and even formation of pulmonary, renal, or central nervous