title: Idiopathic CD4 lymphocytopenia.
abstract: OBJECTIVE
  A severe decrease of CD4 T cells predisposes humans to opportunistic infections. In adults, HIV is certainly the most common cause of CD4 lymphocytopenia, but other causes, such as infections, autoimmune diseases, immunosuppressive therapy, lymphoma and idiopathic forms need to be considered. This review summarizes the current knowledge of the poorly understood syndrome of idiopathic CD4 lymphocytopenia.
  
  
  RESULTS
  Little research has tried to systematically dissect this probably heterogeneic syndrome after its initial description in 1992. Numerous cases presenting with opportunistic infections have been reported. Disturbed differentiation of stem cell precursors may contribute to CD4 lymphocytopenia. Because infections and lymphoma may also cause CD4 lymphocytopenia, the distinction between cause and effect may evolve only during follow-up.
  
  
  CONCLUSIONS
  The manifestation of opportunistic infections calls for the evaluation of the immune system for CD4 lymphocytopenia. The differential diagnosis of this condition in adults comprises primarily HIV infection and less often other diseases or drugs. Idiopathic CD4 lymphocytopenia is very rare. The clinical significance of low CD4 cell counts in HIV negative patients still awaits its systematic analysis. Prophylaxis of opportunistic infections is oriented at the recommendations of HIV-infected individuals and causal treatment remains experimental.
authors.affiliation: Division of Rheumatology and Clinical Immunology, Freiburg University Hospital, Freiburg, Germany.
authors.forename: Ulrich A
authors.initials: UA
authors.lastname: Walker
authors.forename: Klaus
authors.initials: K
authors.lastname: Warnatz
mesh_terms: D001327:Autoimmune Diseases / Q000453:epidemiology / Q000235:genetics / Q000276:immunology*; D018791:CD4 Lymphocyte Count; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D003937:Diagnosis, Differential; D015658:HIV Infections / Q000276:immunology; D006801:Humans; D007156:Immunologic Memory; D016130:Immunophenotyping; D008231:Lymphopenia / Q000453:epidemiology / Q000235:genetics / Q000276:immunology*; D009894:Opportunistic Infections / Q000453:epidemiology / Q000276:immunology; D010641:Phenotype