Introduction. Granulomatous lesions are commonly encountered abnormalities in pulmonary pathology, and often pose a diagnostic challenge. We report an unusual case of granulomatous lung disease with uncommon characteristics, which developed following Epstein-Barr-virus-induced mononucleosis and new-onset systemic lupus erythematosus. We aim to highlight a diagnostic approach for the condition and to raise awareness of the possibility of it being related to the immunological reaction caused by Epstein-Barr virus infection. Case presentation. A 36-year-old Japanese man, who had been diagnosed with Epstein-Barr-virus-induced infectious mononucleosis, new-onset systemic lupus erythematosus, and secondary Sjögrens syndrome three weeks previously, presented to our facility with fever and diffuse pulmonary infiltrates. A computed tomography scan of the chest revealed multiple small nodules in both lungs. Fiberoptic bronchoscopy with bronchoalveolar lavage revealed lymphocytosis with predominance of T lymphocytes. A histological examination of a lung biopsy taken during video-assisted thoracic surgery showed randomly distributed tiny granulomatous lesions with infiltration of eosinophils. The differential diagnoses included hypersensitivity pneumonitis, sarcoidosis, and pulmonary involvement of Crohns disease, systemic lupus erythematosus, and Sjögrens syndrome, but the clinical and pathological findings were not consistent with any of these. Our patients condition did not improve; therefore, prednisolone therapy was started because of the possibility of specific immunological reactions associated with Epstein-Barr virus infection. After steroid treatment, our patient showed radiological and clinical improvement. Conclusions: To the best of our knowledge, this is the first case of a patient developing randomly distributed multiple granulomatous lung lesions with eosinophilic infiltrates after Epstein-Barr virus infection and systemic lupus erythematosus. On the basis of our data, we hypothesize that Epstein-Barr virus infection altered the immune response of our predisposed patient and contributed to the pathogenesis of the lung lesions. Our patients clinical response to steroid treatment was excellent.
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