A nearly fatal primary Epstein-Barr virus infection associated with low NK-cell counts in a patient receiving azathioprine: a case report and review of literature oleh Minna Honkila, Riitta Niinimäki, Mervi Taskinen, Outi Kuismin, Kaisa Kettunen, Janna Saarela, Sami Turunen, Marjo Renko, Terhi Tapiainen