Physicians are often confronted with the dilemma of nonresolving or slowly resolving pulmonary infiltrates in patients receiving antibiotics for suspected community-acquired pneumonia (CAP). Nonresolution or slow resolution of pneumonia may reflect inadequate antibiotic therapy, resistant or highly virulent organisms, impaired host defenses, nonbacterial causes, obstructing endobronchial lesions (including neoplasms), and a host of noninfectious causes. When should these alternative causes be considered in patients with nonresolving or slowly resolving infiltrates? How long should one wait before embarking on a costly investigation to evaluate reasons for nonresolution? What is the normal or expected rate of resolution for pneumonia? What is the “safe” time interval for expectant observation? These decisions should be guided by the natural history of pneumonias (with knowledge of specific pathogens) and various host factors. Although a staggering array of diseases and clinical syndromes can masquerade as CAP, <sup>43 Corley D.E., Winterbauer R.H. Infectious diseases that result in slowly resolving and chronic pneumonia Semin Respir Infect 1993 ;  8 : 3-13

Cliccare qui per andare alla sezione Riferimenti, 85 Gross T., Chavis A.D., Lynch J.P. Noninfectious pulmonary diseases masquerading as community-acquired pneumonia Clin Chest Med 1991 ;  12 : 363-393

Cliccare qui per andare alla sezione Riferimenti, 151 Lynch J.P., Sitrin R.G. Noninfectious mimics of community-acquired pneumonia Semin Respir Infect 1993 ;  8 : 14-45

Cliccare qui per andare alla sezione Riferimenti, 194 Orens J.B., Sitrin R.G., Lynch J.P. The approach to non-resolving pneumonia Med Clin North Am 1994 ;  78 : 1143-1171

Cliccare qui per andare alla sezione Riferimenti</sup> these are far outnumbered by true cases of pneumonia. In this article the authors discuss the patterns of radiographic resolution for CAP and host factors that influence natural history. They also review diverse noninfectious disorders that can mimic CAP, and present an approach to diagnosis and treatment.