pulmonary disorders
Pneumonia in Immunocompromised Patients
Diagnosis of Pneumonia in Immunocompromised Patients
Chest x-ray Assessment of oxygenation Sputum induction or bronchoscopy to obtain lower respiratory samples Blood cultures Pathogens predicted based on symptoms, x-ray changes, and type of immunodeficiency and assessment of oxygenation (usually by pulse oximetry) are done in immunocompromised patients with respiratory symptoms, signs, or fever. If an infiltrate or hypoxemia is present, diagnostic studies should be done. Chest x-ray may be normal in Pneumocystis jirovecii Pneumonia , but hypoxia or an increased alveolar-arterial oxygen gradient is usually present. If clinical suspicion of pneumonia is high and the chest x-ray shows no or minor abnormalities, a chest CT scan should be done. and blood cultures are done. Sputum testing should include Gram stain, mycobacterial and fungal stains and cultures, and sometimes testing for viruses (eg, polymerase chain reaction for cytomegalovirus in a transplant patient or in a patient with AIDS). If signs, symptoms, or risk factors for Pathophysiology are present, serum It is important to aggressively pursue a microbiological diagnosis with induced sputum, bronchoscopy, or both, especially in patients with severe defects in immune function or failure to respond to broad-spectrum antibiotics. Molecular testing that detects pathogen-specific nucleic acids or antigens is being increasingly used to determine the microbial cause. Likely pathogens can often be predicted based on symptoms, x-ray changes, and the type of immunodeficiency. In patients with acute symptoms, the differential diagnosis includes bacterial infection, hemorrhage, pulmonary edema, a leukocyte agglutinin reaction to transfusion of blood products, and pulmonary emboli. An indolent time course is more suggestive of a fungal or mycobacterial infection, an opportunistic viral infection, Pneumocystis jirovecii Pneumonia , tumor, a cytotoxic drug reaction, or radiation injury. X-rays showing localized consolidation usually indicate an infection involving bacteria, mycobacteria, fungi, orNocardiaspecies. A diffuse interstitial pattern is more likely to represent a viral infection,P. jiroveciipneumonia, drug or radiation injury, or pulmonary edema. Diffuse nodular lesions suggest mycobacteria,Nocardiaspecies, fungi, or tumor. Cavitary disease suggests mycobacteria,Nocardiaspecies, fungi, or bacteria, particularlyS. aureus. In organ or bone marrow transplantation recipients with bilateral interstitial pneumonia, the usual cause is cytomegalovirus, or the disease is idiopathic. A pleural-based consolidation is usuallyAspergillusinfection. In patients with acquired immunodeficiency syndrome (AIDS), bilateral pneumonia is usually Pneumocystis jirovecii Pneumonia . About 30% of patients with human immunodeficiency virus (HIV) infection have 