As HIV infection progresses, it creates increasing immunosuppression, resulting in a predisposition to complicating opportunistic infections and neoplasms. The pattern of these complications can be predicted by following a patient’s absolute CD4+ lymphocyte count. On the basis of these correlations between absolute CD4+ lymphocytes and the predicted complications of HIV infection, clinicians can anticipate an increased risk of certain opportunistic infections in an individual patient, which may lead to an earlier diagnosis or the use of antimicrobial prophylaxis to prevent specific opportunistic infections. Successful prophylaxis has been identified against PCP, toxoplasmic encephalitis, disseminated Mycobacterium avium complex (MAC) infection, cryptococcal meningitis, and cytomegalovirus (CMV) disease (

Table 419-2).

Persons at highest risk for PCP include those recovering from their first episode (secondary prophylaxis, 1-year risk of recurrence without prophylaxis 60%), those with absolute CD4+ lymphocytes less than or equal to 200/mm³ (primary prophylaxis, 1-year risk of PCP 18%), those with CD4+ lymphocyte percentages less than 20%, and those with a non-PCP AIDS indicator condition (both primary prophylaxis). Sulfamethoxazole/trimethoprim (SMX-TMP) is the most successful prophylaxis against PCP. In patients intolerant of SMX-TMP, desensitization may be undertaken or dapsone, atovaquone, or aerosolized pentamidine may be used. SMX-TMP and dapsone-pyrimethamine can also be given to prevent toxoplasmic encephalitis among patients who are seropositive for previous infection with Toxoplasma gondii.

Clarithromycin, azithromycin, or rifabutin can delay disseminated MAC infection. These drugs are prescribed for patients at highest risk, usually those with absolute CD4+ lymphocytes less than 100/mm³ . Fluconazole has also demonstrated efficacy in delaying invasive fungal infections in patients with absolute CD4+ lymphocytes less than 200/mm³ . Oral ganciclovir has also successfully delayed the onset of CMV disease in seropositive HIV-infected patients. The widespread use of these prophylaxes must include consideration of their potential drug interactions, the potential for drug resistance, and cost effectiveness.

PCP was once the most common AIDS indicator condition, but HIV-associated wasting, disseminated MAC infection, and CMV disease are now more common clinical manifestations. Overall, the incidence of opportunistic infections has declined with the use of potent antiretroviral combinations. Undoubtedly, the future complications of progressive HIV infection will continue to evolve as improved antiretroviral therapies and prophylactic strategies against additional opportunistic infections are identified and as survival lengthens for persons with AIDS.

When patients do develop opportunistic infections, clinicians should attempt to establish a diagnosis and initiate treatment as soon as possible. Early diagnosis results in an improved prognosis for most opportunistic infections, and with early diagnosis many patients may receive outpatient therapy. Successful outpatient therapy frequently results in greater patient satisfaction and lower health care costs.