[Metastatic Pulmonary Calcification: A Rare Entity in the Differential Diagnosis Examination of Interstitial Lung Diseases].

A 70-year-old patient who received a kidney transplant about 20 years ago due to anti-neutrophil cytoplasmic antibody (ANCA)-positive, rapidly progressive glomerulonephritis was assigned to us for an evaluation of fibrosing interstitial lung disease with computer tomography (CT)-radiological changes assigned to acute alveolitis. She complained about long-term exertional dyspnea. In terms of lung function, there was some slight restriction (FVC 78 % of the target), and pronounced severe diffusion disorder (DLCO 41 % of the target). There was no evidence of exogenous allergic alveolitis in either the history or serology. In the bronchoscopically obtained samples, changes in the sense of a non-specific interstitial lung disease of the fibrotic type, e. g., matching a reaction in the context of immunosuppressive therapy, were observed. Herpes simplex virus was detected microbiologically in the bronchoalveolar lavage (BAL) fluid using the polymerase chain reaction (PCR). Antiviral therapy was carried out under the working diagnosis of herpes pneumonitis. Immunosuppressive therapy was continued. The herpes virus could no longer be detected in a control. The patient initially reported subjective improvement of dyspnea. Repeated control CT imaging was carried out and after about one year, the initial radiological changes were still present and dyspnea was persistent. A new transbronchial lung biopsy revealed metastatic pulmonary calcification. Fortunately, the disease was not active. CONCLUSION:  In the differential diagnostic evaluation of interstitial lung diseases, especially in patients with a vulnerable calcium-phosphate balance and acid-base balance, as occurs, for example, in the context of chronic kidney diseases, the possibility of metastatic pulmonary calcification (MPC) must also be considered especially if the radiological picture shows persistent, upper lobe-accentuated ground glass opacities. The diagnosis requires multidisciplinary cooperation between pulmonologists, radiologists and pathologists.