A. Introduction. In patients infected with HIV, a physician must consider many different possible diagnoses in the setting of a new symptom. These diagnoses include diseases that may occur in nonimmunocompromised patients, as well as opportunistic infections and malignancies that present more frequently in patients with HIV. Furthermore, HIV-infected patients may present with protean symptoms such as fever and weight loss, instead of classic manifestations of disease that may be produced by a vigorous inflammatory response. The list of possible diagnoses can often be simplified because patients infected with HIV acquire opportunistic infections and malignancies at relatively predictable CD4 counts. Therefore, a recent CD4 count may help you exclude etiologies of disease more likely at greater degrees of immunosuppression. Remember, however, that patients with very low CD4 counts may develop any of the conditions noted.
Remember that a CD4 count obtained during an acute illness may be falsely low or falsely high. Whenever possible, it is best to use the most recent CD4 count before the development of acute illness.
B. Differential Diagnoses According to CD4 Count. CD4 counts should only be used as a general guide because there is a great deal of variability among patients. Common diseases that occur as the CD4 count falls are discussed here.
a. CD4 count >200 cells/µL
i. Bacterial infection. Pneumococcal pneumonias are common.
ii. Pulmonary tuberculosis. Both primary tuberculosis and reactivation disease can occur at relatively high CD4 counts. As CD4 counts drop below 200 cells/µL, less common manifestations such as extrapulmonary tuberculosis and miliary tuberculosis are encountered more frequently. Extrapulmonary sites may include the central nervous system (CNS), peritoneum, lymph nodes, pleura, and bone and joints.
iii. Lymphoma. B-cell lymphomas are more common in HIV-infected patients at any CD4 count, and diagnosis of B-cell lymphoma in any individual should prompt HIV testing even in the absence of known risk factors. In patients with CD4 counts in this range, lymphomas are common. Primary CNS lymphomas usually occur only with lower counts.
iv. Kaposi’s sarcoma. Patients may have pulmonary and gastrointestinal involvement as well as the typical cutaneous lesions.
v. Herpes zoster. Herpes zoster may present with a multidermatomal or single-dermatome distribution.
b. CD4 count <200 cells/µL
i. Pneumonia may be caused by Pneumocystis jirovecii (formerly carinii) (see Chapter 56).
ii. Cryptococcus species infection is a common cause of meningitis.
iii. Coccidioidomycosis (Valley fever), caused by the fungus Coccidioides, may manifest as pneumonia, meningitis, or skin and soft tissue infection.
iv. Histoplasmosis, caused by the fungus Histoplasma, can cause pulmonary disease or disseminate with pulmonary, hepatic, bone marrow, and CNS involvement as well as fungemia.
v. Extrapulmonary or miliary tuberculosis. See B. a. ii.
vi. Progressive multifocal leukoencephalopathy (PML). Caused by JC virus, PML can lead to focal neurologic deficits (see Chapter 58).
c. CD4 count <100 cells/µL
i. Toxoplasmosis often manifests with CNS disease (see Chapter 58).
ii. Cryptococcosis most commonly causes meningitis, but patients may have pulmonary or cutaneous disease as well.
iii. Candida esophagitis. Although other manifestations of candidiasis may present at higher CD4 counts, esophagitis tends to be seen in patients with more impaired immunity.
d. CD4 count <50 cells/µL
i. Disseminated Mycobacterium avium complex (MAC) infection usually causes fever, cytopenias, and cachexia. It may also present with diffuse lymphadenopathy of uncertain cause.
ii. Cytomegalovirus (CMV) infection. Retinitis, esophagitis, colitis, AIDS cholangiopathy, and polyradiculopathy may all be seen with CMV infection.
iii. Primary CNS lymphoma (see Chapter 58).
Suggested Further Readings
Akgun KM, Miller RF. Critical care in human immunodeficiency virus-infected patients. Semin Respir Crit Care Med 2016;37:303–17.Find this resource:
Johns Hopkins POC-IT HIV Guide. Johns Hopkins Medicine, 2004. (Accessed Nov 10, 2017, at https://www.hopkinsguides.com/hopkins/index/Johns_Hopkins_HIV_Guide/.)
Panel on Opportunistic Infections in HIV-Infected Adults and Adolescents. Guidelines for the prevention and treatment of opportunistic infections in HIV-infected adults and adolescents: recommendations from the Centers for Disease Control and Prevention, the National Institutes of Health, and the HIV Medicine Association of the Infectious Diseases Society of America. 2017. (Accessed November 15, 2017, at http://aidsinfo.nih.gov/contentfiles/lvguidelines/adult_oi.pdf.)