<prompt> A 3-year-old child presented with fatigue, malaise, fever, sore throat, headache, nausea, abdominal pain and myalgia. OE Generalized lymphadenopathy Hepatosplenomegaly Tonsillar enlargement Palatal petechiae Rashes and edema of the eyelids. the above condition cant occur in which of the following: -X-linked agammaglobulinemiaMultiple myelomaDiGeorge syndromeWiskott-aldrich syndrome  <response>: This is a case of Infectious mononucleosis. So, there are no B-cells in X-linked agammaglobulinemia to be affected. In rest all the 3 conditions, B-cells are normal. Di-George and Wiskott-aldrich syndrome are T-cell deficiencies. 1st image shows tonsillitis with membrane formation Peripheral blood film shows atypical lymphocytes or Downey cells are lymphocytes that become large as a result of antigen stimulation. B cells are the main reservoir of infection. An EBV envelope glycoprotein binds CD21 CR2, the receptor for the C3d component of complement, which is present on B cells. 