Acquired Pure Red Blood Cell Anemia

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Chapter 444 Acquired Pure Red Blood Cell Anemia

Transient Erythroblastopenia of Childhood

Transient erythroblastopenia of childhood (TEC) is the most common acquired red cell aplasia occurring in children. It is more prevalent than congenital hypoplastic (Diamond-Blackfan) anemia. This syndrome of severe, transient hypoplastic anemia occurs mainly in previously healthy children between 6 mo and 3 yr of age, and most of the children are older than 12 mo at onset. Only 10% of affected patients are >3 yr of age. The annual incidence is estimated to be up to 4.3 cases per 100,000 children, although it is likely higher, because many cases might go undiagnosed and resolve spontaneously. The suppression of erythropoiesis has been linked to immunoglobulin (Ig)G, IgM, and cell-mediated mechanisms. Familial cases have been reported, suggesting a hereditary component. TEC often follows a viral illness, although no specific virus has been implicated consistently. A study of acute cases found no proof that human herpesvirus (HHV)-6, parvovirus B19, Epstein-Barr virus (EBV), or cytomegalovirus (CMV) is a causative agent.

The temporary suppression of erythropoiesis results in reticulocytopenia and moderate to severe normocytic anemia. Some degree of neutropenia occurs in up to 20% of cases. Platelet numbers are normal or elevated. Similar to the situation observed in iron-deficiency anemia and other red blood cell (RBC) hypoplasias, thrombocytosis is presumably caused by increased erythropoietin, which has some homology with thrombopoietin. Mean corpuscular volume (MCV) is characteristically normal for age, and fetal hemoglobin (HbF) levels are normal before the recovery phase. RBC adenosine deaminase (ADA) levels are normal in this disorder, thus contrasting with the elevation noted in most cases of congenital hypoplastic anemia (Table 444-1). Differentiation from the latter disease is sometimes difficult, but differences in age at onset and in age-related MCV, HbF, and ADA are usually helpful. The peak occurrence of TEC coincides with that of iron-deficiency anemia in infants receiving milk as their main caloric source; differences in MCV should help to distinguish between these 2 disorders.

Table 444-1 COMPARISON OF DIAMOND-BLACKFAN ANEMIA AND TRANSIENT ERYTHROBLASTOPENIA OF CHILDHOOD

FEATURE DBA TEC
Male : female 1.1 1.3
Age at diagnosis, male (mo)
Mean 10 26
Median 2 23
Range 0-408 1-120
Age at diagnosis, female (mo)
Mean 14 26
Median 3 23
Range 0-768 1-192
Boys >1 yr 9% 82%
Girls >1 yr 12% 80%
Etiology Genetic Acquired
Antecedent history None Viral illness
Physical examination abnormal 25% 0%
Laboratory
Hemoglobin (g/dL) 1.2-14.8 2.2-12.5
WBCs <5,000/µL 15% 20%
Platelets >400,000/µL 20% 45%
Adenosine deaminase Increased Normal
MCV increased at diagnosis 80% 5%
MCV increased during recovery 100% 90%
MCV increased in remission 100% 0%
HbF increased at diagnosis 100% 20%
HbF increased during recovery 100% 100%
HbF increased in remission 85% 0%
i Antigen increased 100% 20%
i Antigen increased during recovery 100% 60%
i Antigen increased in remission 90% 0%

DBA, Diamond-Blackfan anemia; HbF, fetal hemoglobin; MCV, mean cell volume; TEC, transient erythroblastopenia of childhood; WBC, white blood cell.

From Nathan DG, Orkin SH, Ginsburg D, et al, editors: Nathan and Oski’s hematology of infancy and childhood, ed 6, vol 1, Philadelphia, 2003, WB Saunders, p 329. Adapted from Alter BP: The bone marrow failure syndromes. In Nathan DG, Oski FA, editors: Hematology of infancy and childhood, ed 3, Philadelphia, 1987, WB Saunders, p 159; and Link MP, Alter BP: Fetal erythropoiesis during recovery from transient erythroblastopenia of childhood (TEC), Pediatr Res 15:1036–1039, 1981.

Virtually all children recover within 1-2 mo. RBC transfusions may be necessary for severe anemia in the absence of signs of early recovery. The anemia develops slowly, and significant symptoms usually develop only with severe anemia. Corticosteroid therapy is of no value in this disorder. Any child with presumed TEC who requires >1 transfusion should be re-evaluated for another possible diagnosis. In rare instances, a prolonged case of apparent TEC may be caused by parvovirus-induced RBC aplasia, occurring in children with congenital or acquired immunodeficiencies.

Red Cell Aplasia Associated with Parvovirus B19 Infection

Parvovirus B19 is a common infectious agent that causes erythema infectiosum (fifth disease) (Chapter 243). It is also the best-documented viral cause of RBC aplasia in patients with chronic hemolysis, patients who are immunocompromised, and fetuses in utero. The virus is particularly infective and cytotoxic in marrow erythroid progenitor cells, interacting specifically with the RBC P antigen. In addition to decreased or absent erythroid precursors, characteristic nuclear inclusions in erythroblasts and giant pronormoblasts may be seen under the light microscope in bone marrow specimens.

Miscarriage and Hydrops Fetalis

Parvovirus infection and destruction of erythroid precursors can also occur in utero. Such events are associated with increased fetal wastage in the first and second trimesters. Infants may be born with hydrops fetalis (Chapter 97) and viremia. The presence of persistent congenital parvovirus infection is detected by PCR of peripheral blood and/or bone marrow DNA, because immunologic tolerance to the virus can prevent the usual development of specific antibodies.