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HIV and tuberculosis :. HIV infection is a risk factor for the development of tuberculosis. HIV infection results in a progressive decline in immune function, characterised by a loss of CD4+ T lymphocytes eventually resulting in the patient developing one or more opportunistic diseases. Tuberculosis is one of those opportunistic diseases and pulmonary tuberculosis has been included as an AIDS defining illness in the AIDS case-definition used in the United States. In Hong Kong before July 1995, only the extrapulmonary form of tuberculosis was included as the primary AIDS-defining illness. From July 1995 onwards, the pulmonary or cervical lymph node involvement of TB have also been included as primary AIDS-defining illnesses in Hong Kong if the CD4 count is less than 200/ml. A person with HIV infection may develop tuberculosis as a result of:
The clinical presentation of HIV-associated tuberculosis is dependent on the degree of underlying immuno-deficiency. Tuberculosis often occurs relatively early in the course of immune deficiency. In the earliest stages of HIV disease, the presentation is similar to that of patients without HIV infection. As patients become more immuno-suppressed, the presentation becomes increasingly atypical and disseminated. Overall, HIV positive patients are more likely to have extra-pulmonary disease than HIV negative patients. There are specific problems in:
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