Case 219. 
Parvovirus B19-induced hydrops fetalis (25 f-w F, prematurity)
    Intrauterine fetal death at the 25th week of gestation, showing hydrops fetalis (the mother suffered from erythema infectiosum at the 10th week of gestation)    
Key words : parvovirus B19, hydrops fetalis, erythema infectiosum
The fetus weighing 1,010 g shows features of hydrops fetalis. Mild maceration is observed (gross findings).   In the internal organs, the markedly anemic (pale yellowish brown-colored) liver is quite characteristic (gross findings). The fetus with hepatic hematopoiesis (19-29 weeks of gestation) is susceptible to this single-stranded DNA virus.
Eosinophilic nuclear inclusions with chromatin margination at the periphery of the nuclei are observed in the erythroblasts located in the capillary of the lung tissue (HE).   Immunostaining for parvovirus B19 antigen demonstrates distinct nuclear reactivity in the infected erythroblasts.
Erythroblasts in the lumen of capillary vessels of the placental villi show eosinophilic nuclear inclusions (HE).   Electron micrograph of an autolytic erythroblast in the lung capillary vessel. The nuclear inclusion compresses chromatin at the periphery of the nucleus.
Electron micrograph of the nuclear inclusion in an erythroblast. Numerous small-sized (20 nm in diameter) viral particles without elvelop formation are clustered.