Congenital pure RBC aplasia (Diamond-Blackfan syndrome), a lifelong disorder, usually presents in the first few months of life or at birth with severe anemia and mild macrocytosis or a normocytic anemia. It is due to a deficiency of bone marrow red blood cell precursors (Table 150-6). More than a third of patients have short stature. Many patients (50% to 66%) respond to corticosteroid treatment, but must receive therapy indefinitely. Patients who do not respond to corticosteroid treatment are transfusion dependent and are at risk of the multiple complications of long-term transfusion therapy, especially iron overload. These patients have a higher rate of developing leukemia or other hematologic malignancies than the general population.
In contrast to the congenital hypoplastic anemias, transient erythroblastopenia of childhood, a normocytic anemia causedby suppression of RBC synthesis, usually appears after 6 monthsof age in an otherwise normal infant. Viral infections are thoughtto be the trigger, although the mechanism leading to RBC aplasia is poorly understood. The onset is gradual, but anemia maybecome severe. Recovery usually is spontaneous. Differentiationfrom Diamond-Blackfan syndrome, in which erythroid precursors also are absent or diminished in the bone marrow, may bechallenging. Transfusion of packed RBCs may be necessary ifthe anemia becomes symptomatic before recovery.
Aplastic crises may complicate any chronic hemolytic anemia. These periods of severe reticulocytopenia, leading to an acute exacerbation of the anemia, may precipitate cardiovascular decompensation. Human parvovirus B19 (the cause of fifth disease) infects erythroid precursors and shuts down erythropoiesis. Transient erythroid aplasia is without consequence in individuals with normal RBC survival. Recovery from parvovirus infection in hemolytic disease is spontaneous, but patients may need transfusion if the anemia is severe.
SEE FIGURE 150-1.
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Etiology. Pancytopenia is a quantitative decrease in formed elements of the blood—erythrocytes, leukocytes, and platelets. Patients more often exhibit symptoms of infection or bleeding than anemia because of the relatively short life span of WBCs and platelets compared with the life span of RBCs. Causes of pancytopenia include failure of production (implying intrinsic bone marrow disease), sequestration (hypersplenism), and increased peripheral destruction.
Differential Diagnosis. Features that suggest bone marrow failure and mandate an examination of bone marrow include a low reticulocyte count, teardrop forms of RBCs(implying marrow replacement, not just failure), presenceof abnormal forms of leukocytes or myeloid elements lessmature than band forms, small platelets, and an elevatedmean corpuscular volume in the face of a low reticulocytecount. Pancytopenia resulting from bone marrow failure isusually a gradual process, starting with one or two cell lines, but later involving all three cell lines. Features suggestingincreased destruction include reticulocytosis, jaundice,immature erythroid or myeloid elements on the blood smear,large platelets, and increased serum bilirubin and lactic dehydrogenase.
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