Differential diagnostic of community-acquired pneumonia and disseminated disease Abstract. We analyze the case of the differential diagnosis of community-acquired pneumonia and disseminated disease at soldiers. Recently, there has been an increase in the share of patients with disseminated processes in lungs. To some extent, it is explained by the improvements in diagnostics, but as to our opinion, there is a real rise in morbidity. A relatively high fatality rate in cases of disseminated lung diseases results from lack of awareness among doctors, insufficient technical equipment of medical centres, difficulties in differential diagnostics due to the absence of pathognomonic signs, and the fatal character of some disseminated lung diseases. Diagnostic mistakes in these patients constitute 75–80%. There is no universal algorithm for diagnosing such diseases yet. In most guidelines, the following succession of diagnostic stages can be found: detailed study of the past medical history and clinical symptoms of the disease; doing a computed tomography scan, studying the biopsy sample. Morphological verification of the diagnosis is the golden standard of the diagnostics of idiopathic interstitial lung diseases. The introduction of diagnostic open and videothoracoscopic biopsy of the lung into clinical practice allowed us to avoid a large number of diagnostic mistakes. As a rule, a thorough analysis of the whole complex of clinical X-ray and morphological changes is necessary to make the final nosological diagnosis. In the course of providing specialized medical aid in the Military Medical Academy clinics, complex hi-tech X-ray diagnostics was carried out with the use of spiral computer tomography and modern immunohistochemical analysis, thanks to which a soldier was diagnosed with langerhans cell histiocytosis X. Key words: soldiers, disseminates lung diseases, langerhans cell histiocytosis X, spiral computer tomography, videothoracoscopic biopsy, immunohistochemical analysis. Контактный телефон: 8-(903)-096-15-01; e-mail: Sea-89@yandex.ru