Diagnosis of parvovirus B19 infection can bechallenging in patients with severe immunocompromise as they are usually unable tomount neutralizing antibodies to clear the virus, and serology for anti-parvovirusB19 is usually negative or show weak titers of IgM alone.6 This was the case of our patient; despite her prior infection, her serologywas only positive for anti-parvovirus IgM and negative for anti-parvovirus IgG. This evidence concerns the gene CD40LG and infection.