A 3-year-old child presented with fatigue, malaise, fever, sore throat, headache, nausea, abdominal pain and myalgia. O/E Generalized lymphadenopathy Hepatosplenomegaly Tonsillar enlargement Palatal petechiae Rashes and edema of the eyelids. the above condition can't occur in which of the following: -

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.