An infant girl with persistent lymphopenia was found to have plasma cells in her bone marrow and, for her age, normal amounts of immunoglobulins (IgA, IgG, and IgM) in her serum. She died at age 4 months from giant cell pneumonia proven to be due to measles virus. Postmortem examination revealed no identifiable thymus. There was an almost complete absence of small lymphocytes in the lymph nodes, spleen, and intestines, but plasma cells were present in these tissues. Two sisters who had died earlier of pneumonitis—one with giant cell pneumonia— also had the same type of immunological defect. Since the Swiss type of thymic aplasia is associated with absent plasma cells and agammaglobulinemia, these patients belong to a variant of this syndrome which points to a dissociation between the development of lymphocytes and plasma cells. The increased susceptibility of two of the three infants to measles infection and other clinical and laboratory observations suggests that lymphocytes play an important role in host resistance to this viral infection.
Nahmias AJ, Griffith D, Salsbury C, Yoshida K. Thymic Aplasia With Lymphopenia, Plasma Cells, and Normal ImmunoglobulinsRelation to Measles Virus Infection. JAMA. 1967;201(10):729–734. doi:10.1001/jama.1967.03130100027008