Maternal history:
(1) skin rash during early to mid-pregnancy
(2) severe anemia from red cell aplasia or transient aplasia
(3) typically asymptomatic
Placental changes:
(1) hydrops with pallor and edema
(2) villitis with necrosis and calcifications
(3) endothelial damage in the umbilical artery and stem arteries with lymphocytic inflammation
(4) hemosiderin-ladened macrophages in the chorionic layer of the membranes
Fetal or neonatal changes:
(1) intrauterine fetal demise, often during the second trimester
(2) hydrops fetalis
(3) severe anemia with reduced normoblasts
(4) hepatitis
(5) myocarditis
Histologic features of infected cells:
(1) intranuclear eosinophilic inclusion within normoblasts in the placenta
(2) intranuclear eosinophilic inclusion within normoblasts and pronormoblasts in the bone marrow
(3) positive immunohistochemistry or in situ hybridization within nuclei of normoblasts, myocytes or other infected cells
Additional testing:
(1) PCR (more sensitive than intranuclear inclusions)
(2) electron microscopy to demonstrate virions
(3) seroconversion in the mother with IgM antibodies
