Severe hypoplasia of lymphoid tissues in Mo1 deficiency.

A lymph node was examined from a 4-year-old female child with documented "Mo1" (CR3) deficiency. There was hypoplasia of the lymph node, with small, poorly delineated germinal centers and overall lymphopenia. Retrospective analysis of the clinical course of a decreased elder sister of the index patient indicated that the elder sister probably also had "Mo1" deficiency. Review of findings at autopsy revealed severe hypoplasia of all lymphoid organs with lymphopenia. Our observations suggest that lymphoid tissue hypoplasia may be a feature of CR3 deficiency and is likely a result of the defective lymphocyte adherence functions to endothelium associated with absent lymphocyte function-associated antigen (LFA-1).