Pneumocystis carinii pneumonia as a complication of immunosuppressive therapy

Patients receiving immunosuppressive therapy with corticosteroids and cytotoxic agents may develop opportunistic infections such as Pneumocystis carinii pneumonia (PCP). This indicates a severe T-cell defect, but so far there are no established criteria for identifying patients at risk.

CD4+ and CD8+ T-lymphocyte counts were determined by flow cytometry in seven HIV-negative patients who developed PCP as a complication of immunosuppressive treatment.

CD4+ T-lymphocyte counts (T-helper phenotype) were less than 200/microl in all seven patients (mean 90.6/microl). The markedly reduced CD4 counts measured in these patients are similar to those observed in organ transplant recipients who developed PCP during immunosuppressive therapy for prevention of graft rejection and in HIV-positive patients with PCP as an AIDS-defining illness.

Measuring CD4+ T-lymphocyte counts may be helpful in determining the risk of PCP not only in HIV-positive patients, but also in patients receiving immunosuppressive therapy. The risk of acquiring PCP seems to increase when CD4+ lymphocyte counts drop below 200/microl, regardless of the underlying disease.