Chapter 4: Pure Red Cell Aplasia

DEFINITION

• Pure red cell aplasia describes anemia caused by an isolated depletion of erythroblasts characterized by severe reticulocytopenia and absent or markedly diminished marrow erythroid progenitors (erythroblasts).

CLASSIFICATION

• See Table 4–1.

ACUTE RED CELL APLASIA

• May result from transient marrow erythroblastopenia, which occurs in both children and adults. It is most common in the first several years of life.

• Seen most often in patients with a hemolytic disorder, such as hereditary spherocytosis or sickle cell anemia, when a transient severe reduction in erythropoiesis causes a rapid fall in hemoglobin level—called an (erythroid) aplastic crisis.

• May also be seen in patients who are hematologically normal.

• True prevalence is unknown, and it is assumed that many mild cases are not detected.

Etiology

• Most patients with aplastic crises are infected with B19 parvovirus, but occasionally another viral infection may be responsible.

• IgG inhibitors of erythroid colony formation in vitro have been found in some patients with a condition called transient erythroblastopenia of childhood.

• Drugs may induce aplastic crises, either by an immunologic mechanism or by direct toxicity. Commonly implicated drugs are listed in Table 4–2.

Clinical Features

• Frequently, the patient has had a recent febrile illness, often with upper respiratory symptoms, gastrointestinal symptoms, or headache.

• Listlessness, increasing pallor, and tachycardia are characteristic.

• Usually no other significant changes are found on physical examination.

Laboratory Features

• Evidence of an underlying hematologic disorder, such as hereditary spherocytosis or sickle cell anemia, may be present.

• Anemia and reticulocytopenia are characteristic. They are often severe.

• Granulocyte and platelet counts are usually normal.

• Erythroid cells are depleted in the marrow early in the illness, but reappear just before recovery; thus, if the marrow is tested during recovery, the erythroblastopenia may be missed.

• Reticulocytosis is the first sign of recovery, and some nucleated red cells ...