Bacterial pneumonia

This chest x-ray shows homogenous shadowing involving the lateral aspect of the right upper zone in an HIV-positive patient. Note that the horizontal fissure is raised. These changes are consistent with partial consolidation of the right upper lobe. The most likely diagnosis is a pneumonia due to Streptococcus pneumoniae. This infection is very common in HIV and may occur early in the disease. Pneumococcal bacteraemia (with pneumonia) is also well recognized and blood cultures should be taken if available. The radiological appearances could also be due to tuberculous pneumonia. This diagnosis should be considered in lobar pneumonia that does not respond to antibacterial treatment.