Thoracic Imaging 2003 - Society of Thoracic Radiology

HIV-infection: Primary and Secondary Lung Infection
Linda B. Haramati, M.D.
Objectives:
1. To describe and give examples of the various lung infections
to which HIV-infected patients are predisposed.
2. To describe the changes in distribution of infection with the
waning immunity (as reflected by CD4) that is a usual feature
of untreated HIV-infection.
3. To describe changes in lung disease related to partial
immune restoration by treatment with highly active antiretroviral
therapy (HAART).
Needs and Attributes:
This lecture is designed for radiologists who interpret chest
radiographs and CT scans. All such radiologists should be
familiar with the classic and recent finding of HIV-related pulmonary
infections.
The recognition of HIV-infection in the early 1980’s was
prompted by the description of Kaposi sarcoma in several gay
men, and then by recognition of Pneumocistis carinii pneumonia
(PCP) in patients who did not fit previous categories of immune
compromise. Since that time, HIV-infection has reached epidemic
proportions throughout the world and became a scourge
in the United States. Unlike other forms of immune compromise
such as organ transplantation and congenital immune deficiencies
that are confined to a small population, HIV infection
is widespread. Infection is the most common complication of
HIV-infection and the lung is the most frequently involved
organ. This brief talk will give an overview of the wide variety
of infections that occur in HIV-infected patients, how the
patients’ immune status reflects the type of infections that they
acquire, how HAART with partial immune restoration has
decreased the prevalence of severe immunocompromise and
how it has changed the course of several diseases.
Although PCP is the pulmonary infection thought to be associated
with AIDS, even early in the AIDS epidemic, bacterial
pneumonia was recognized to occur more frequently. Infection
with pneumococcal pneumonia, haemophilus and other usual
species is most common. AIDS patients with bacterial pneumonia
are more frequently bacteremic than their immune-competent
counterparts. Although the incidence of bacterial pneumonia
increases as the patients CD4 decreases, two or more
episodes of bacterial pneumonia in a single year are AIDSdefining
at any CD4 count. The chest radiographic and CT findings
of bacterial pneumonia in HIV-infected patients are similar
to that of the general population, although some authors describe
more frequent multi-lobar involvement and pleural effusion. As a
patient’s immunity wanes, various unusual bacterial infections
including zoonoses are seen in HIV-infected individuals.
PCP is a taxonomic misfit that has bounced from the protozoal
to the fungal category-not fully belonging to either.
Priviously, PCP was a common presenting infection leading to
the diagnosis of AIDS. However, this presentation is currently
uncommon, except in patients who have reduced access to
healthcare. PCP generally occurs in patients with CD4 counts