Despite initial claims to the contrary, a cluster of reports of severe
opportunistic infections occurring in patients without evidence of HI
V infection do not appear to represent a new disease entity or present
evidence of epidemiologically associated cases suggesting an infectio
us agent. Reported cases are reviewed and appear to represent a hetero
geneous group, many of which may represent sporadic cases of late onse
t acquired immunodeficiency. In addition, a small group of asymptomati
c subjects have been identified with constitutively low CD4 T cell pop
ulations which appear to have little or no clinical significance since
these patients have no evidence of clinical immunodeficiency. Newly i
dentified cases should be fully investigated immunologically and virol
ogically after recovery from their presenting infection and continuous
or prophylactic therapy instituted only in cases of substantiated lon
g-term severe immunodeficiency.