Hepatitis-associated aplastic anemia during a primary infection of genotype 1a torque teno virus

A 12-year-old Japanese boy suffered from severe acute hepatitis and pancytopenia. The patient underwent successful bone marrow transplantation from an HLA-identical sister. Torque teno virus (TTV) DNA of genotype 1a and IgM-class antibody against the virus were detected in sera at the onset of hepatitis. TTV/1a DNA and anti-TTV/1a IgM antibody levels were undetectable on the 16th and 46th days after the onset of illness, respectively. Anti-TTV/1a IgG antibody was positive throughout the observation period. Sequential viral load and anti-TTV/1a IgM antibody suggested a primary infection of TTV/1a. Genomic sequence of the virus coincided with that of the original strain first isolated from human. TTV DNA was quantified at 130 copies in 10⁵ bone marrow mononuclear cells, which suggested that infection of hematopoietic cells might be the cause of aplasia. This is the first report of TTV hepatitis-associated aplastic anemia assessed by the anti-TTV antibodies and viral load in peripheral blood and bone marrow.