Clinical Utility of the IRF: Assessment of Erythroid Regeneration Following Parvo B19 Infection

Extract

Parvo B19 (Fifth disease) is an erythrotropic virus which attaches through the ‘P’ globoside receptor on the surface of human red blood cells and precursors. This typically benign viral infection can cause a transient aplastic anemia in patients with underlying red cell disorders. In this case, a two-year-old child presents with severe aplastic anemia without evidence of underlying disease. Erythroid regeneration is monitored through the use of the immature reticulocyte fraction (IRF) and is demonstrated by the presence of high and medium fluorescence reticulocytes in the peripheral blood three to five days prior to the peak in absolute reticulocytes.

Parvovirus B19 (B19) is a species specific, small, nonenveloped, single-stranded DNA virus that belongs to the family Paroviridae, genus Erythrovirus. Discovered by Cossart and colleagues in 1975, it is the only known human pathologic parvovirus associated with a broad spectrum of disorders.¹ Human B19 is considered a ubiquitous virus with distribution worldwide. Cultured from the respiratory tract, Parvovirus B19 is presumed to be transmitted as an aerosol. Prevalence of infection is common, reported at a frequency ranging from 2% to 15% in children one to five years of age, approximately 15% in children ages five to 19 years, with approximately 50% of adults testing seropositive.² Diverse clinical manifestations arise due to B19 infection. Infection follows a cyclic pattern with increased rates occurring every four to five years.³ Infection can present as asymptomatic, cause erythema infectiosum, or induce a polyarthropathy syndrome, a hemolytic anemia, or hydrops fetalis during pregnancy. Severe anemia due…

ABBREVIATIONS: IRF = immature reticulocyte fraction.