Talc is a mineral widely used in the ceramic, paper, plastics, rubber, paint, and cosmetic industries. Four distinct forms of pulmonary disease caused by talc have been defined. Three of them (talcosilicosis, talcoasbestosis, and pure talcosis) are associated with aspiration and differ in the composition of the inhaled substance. The fourth form, a result of intravenous administration of talc, is seen in drug users who inject medications intended for oral use. The disease most commonly affects men, with a mean age in the fourth decade of life. Presentation of patients with talc granulomatosis can range from asymptomatic to fulminant disease. Symptomatic patients typically present with nonspecific complaints, including progressive exertional dyspnea, and cough. Late complications include chronic respiratory failure, emphysema, pulmonary arterial hypertension, and cor pulmonale. History of occupational exposure or of drug addiction is the major clue to the diagnosis. The high-resolution computed tomography (HRCT) finding of small centrilobular nodules associated with heterogeneous conglomerate masses containing high-density amorphous areas, with or without panlobular emphysema in the lower lobes, is highly suggestive of pulmonary talcosis. The characteristic histopathologic feature in talc pneumoconiosis is the striking appearance of birefringent, needle-shaped particles of talc seen within the giant cells and in the areas of pulmonary fibrosis with the use of polarized light. In conclusion, computed tomography can play an important role in the diagnosis of pulmonary talcosis, since suggestive patterns may be observed. The presence of these patterns in drug abusers or in patients with an occupational history of exposure to talc is highly suggestive of pulmonary talcosis.

Leptospirosis, a spirochetal zoonosis, is frequently unrecognized due to its manifestation as an undifferentiated fever. It is an emerging infectious disease that has changed from an occupational disease of veterinarians, farmers, butchers, and other animal handlers to a cause of epidemics in poor and decayed urban communities in developing countries. Humans are infected when mucous membranes or abraded skin come into direct contact with the urine of infected animals, especially rats and dogs. Mortality from severe leptospirosis is high, even when optimal treatment is provided. The diagnosis of leptospirosis is based on clinical findings, history of direct or indirect exposure to infected animals in endemic areas, and positive serological tests. It should be considered in the differential diagnosis of patients with febrile illnesses associated with pneumonitis and respiratory failure, especially when hemoptysis is present. Severe pulmonary involvement in leptospirosis consists primarily of hemorrhagic pneumonitis. In advanced cases, adult respiratory distress syndrome and massive pulmonary hemorrhage may occur. Chest radiographs show bilateral alveolar infiltrates and/or resemble viral pneumonia, bronchopneumonia, tuberculosis, adult respiratory distress syndrome, and other causes of pulmonary hemorrhage such as Goodpasture syndrome. High-resolution computed tomography scans may show nodular infiltrates, areas of consolidation, ground-glass attenuation, and crazy-paving patterns. Bronchoalveolar lavage and autopsy studies have suggested that ground-glass opacities and air-space consolidations are secondary to pulmonary hemorrhage. Although not specific, the presence of these computed tomography findings in a febrile patient with an appropriate history should suggest a diagnosis of leptospirosis.

Congenital chest malformations can range from small and asymptomatic entities to large space-occupying masses that require immediate surgical treatment. They may affect the foregut, pulmonary airway, and vasculature. Hybrid conditions are commonly seen, with interrelated chest malformations having various radiologic and pathologic features. An understanding of the in utero complications associated with fetal chest masses is essential for appropriate monitoring during pregnancy, treatment recommendations, and delivery management. Technologic advances have greatly improved the diagnosis of fetal anomalies. Congenital chest malformations are usually evaluated in the prenatal period with fetal sonography, but fetal magnetic resonance (MR) imaging is a well-established modality that is used as an adjunct technique in difficult diagnostic situations. MR imaging can provide excellent tissue contrast with more accurate analysis of the fetal anatomy and superior differentiation between the abnormalitites and adjacent structures, thereby allowing early planning of prenatal management.

The high-resolution CT features in children with exogenous lipoid pneumonia are air-space consolidations and ground-glass attenuation, occasionally with a crazy-paving pattern, distributed bilaterally in the posterior and lower zones of the lungs.

Kaposi sarcoma is a low-grade mesenchymal tumor involving blood and lymphatic vessels. There are four variants of this disease, each presenting a different clinical manifestation: classic or sporadic, African or endemic, organ transplant-related or iatrogenic, and AIDS-related or epidemic. Kaposi sarcoma is the most common tumor among patients with HIV infection, occurring predominantly in homosexual or bisexual men. The pulmonary involvement in Kaposi sarcoma occurs commonly in critically immunosupressed patients who commonly have had preceding mucocutaneous or digestive involvement.The etiology of Kaposi sarcoma is not precisely established; genetic, hormonal, and immune factors, as well as infectious agents, have all been implicated. There is evidence from epidemiologic, serologic, and molecular studies that Kaposi sarcoma is associated with human herpes virus type 8 infection. The disease starts as a reactive polyclonal angioproliferative response towards this virus, in which polyclonal cells change to form oligoclonal cell populations that expand and undergo malignant transformation.The diagnosis of pulmonary involvement in Kaposi sarcoma usually can be made by a combination of clinical, radiographic, and laboratory findings, together with the results of bronchoscopy and transbronchial biopsy. Chest high-resolution computed tomography scans commonly reveal peribronchovascular and interlobular septal thickening, bilateral and symmetric ill-defined nodules in a peribronchovascular distribution, fissural nodularity, mediastinal adenopathies, and pleural effusions. Correlation between the high-resolution computed tomography findings and the pathology revealed by histopathological analysis demonstrate that the areas of central peribronchovascular infiltration represent tumor growth involving the bronchovascular bundles, with nodules corresponding to proliferations of neoplastic cells into the pulmonary parenchyma. The interlobular septal thickening may represent edema or tumor infiltration, and areas of ground-glass attenuation correspond to edema and the filling of air spaces with blood. These findings are a result of the propensity of Kaposi sarcoma to grow in the peribronchial and perivascular axial interstitial spaces, often as continuous sheets of tumor tissue.In conclusion, radiological findings can play a major role in the diagnosis of pulmonary Kaposi sarcoma since characteristic patterns may be observed. The presence of these patterns in patients with AIDS is highly suggestive of Kaposi sarcoma.