HIV/AIDS (pulmonary and thoracic manifestations)

Pulmonary manifestations of HIV/AIDS are a major contributor to morbidity and mortality related to the disease. The differential in an HIV patient with a chest complaint is broad. Infectious causes are the most common, however, neoplasms, lymphoma and interstitial pneumonia also play a significant role.

A systematic approach that takes into account the imaging findings, the severity of immunosuppression (i.e. CD4 count) and the clinical presentation should narrow the differential.

Epidemiology

Some groups of HIV patients are predisposed to certain associated conditions. For example, lymphocytic interstitial pneumonitis is considerably more common in pediatric patients. Kaposi sarcoma is seen predominantly in the homosexual male population.

Clinical presentation

The type and onset of respiratory complaint may narrow the differential diagnosis.

Acute onset of febrile illness favors bacterial infection. The presence of a productive cough also favors pyogenic infection and points away from pneumocystis pneumonia​.

An insidious onset of symptoms is more typical of tuberculous, non-tuberculous mycobacterial, or fungal infection. Persistent symptoms that do not respond to therapy raise suspicion of a neoplastic process.

CD4 counts

• >200 cells/mm: all patients with HIV are at an increased risk of bacterial infections and TB, the risk increases further as CD4 count drops
• <200 cells/mm: also susceptible to PCP, atypical mycobacteria
• <100 cells/mm: also susceptible to CMV, disseminated fungal and mycobacterial infections

Pathology

The spectrum of thoracic pathologies include :

• bacterial pneumonia
• features secondary to Mycobacterium tuberculosis
• malignancies
  • lung cancer
    • adenocarcinoma
    • squamous cell carcinoma
  • Hodgkin lymphoma
• human Herpes-virus 8-related diseases
  • Kaposi sarcoma
  • multicentric Castleman disease
  • KSHV inflammatory cytokine syndrome
  • primary effusion lymphoma
• other infections
  • pneumocystis pneumonia
  • HIV-associated pulmonary arterial hypertension
• other conditions
  • lymphocytic interstitial pneumonia 
  • multilocular thymic cyst
  • pulmonary embolism 

Radiographic features

Imaging appearances of patients with AIDS-related chest conditions are protean and often non-specific. A pattern-based approach is suggested for narrowing the differential diagnosis.

A chest x-ray is generally the initial examination, however, a CT is often warranted for characterization.

Plain radiograph

Normal chest x-ray

The chest x-ray is not infrequently normal in an HIV patient presenting with a respiratory complaint. Consider:

• upper respiratory tract infection: common in HIV
• radiographically-occult infections such as viral or bacterial bronchiolitis
• imaging patterns that may be difficult to see on plain x-ray, e.g. ground-glass opacity with pneumocystis pneumonia

Focal airspace opacity

Bacterial infection is most likely, of which Streptococcus pneumoniae is most common. In the severely immunosuppressed, consider also TB. A non-resolving airspace opacity may be due to malignancy.

Multifocal airspace opacity

A multifocal bacterial infection is again most likely.

When the opacities are nodular consider fungal infection, mycobacteria and Nocardia asteroides.

Ground-glass opacity

Pneumocystis pneumonia is a common cause of ground-glass opacity in the immunocompromised host: although incidence has decreased with the advent of prophylactic therapy and HAART. Look for the typical perihilar distribution. There may be a crazy-paving appearance.

Other infectious differentials include viral and atypical bacterial infections. In the severely immunocompromised (CD4 count <100 cells/mm), consider CMV pneumonia.

Non-infectious causes of ground-glass opacity include lymphocytic interstitial pneumonitis (with thin wall cysts), or non-specific interstitial pneumonia.