Implication of Immunohistochemistry for Propionibacterium acnes in Differential Diagnosis of Necrotizing Granuloma

Propionibacterium acnes (P. acnes) have been reported to have an etiologic link with sarcoidosis. A 45-year-old Japanese woman complaining of cough for 1 month presented to our hospital. Chest computed tomography showed an irregular nodular shadow in the right upper pulmonary lobe, a finding suggestive of either pulmonary sarcoidosis or tuberculosis. Biopsy specimens from the pulmonary shadow showed necrotizing granulomas, and there were no other findings from the initial laboratory examinations that could provide a definitive diagnosis. However, immunohistochemical staining using a P. acnes-specific monoclonal antibody revealed small round bodies within the granulomas. Based on these results, we diagnosed the patient clinically with sarcoidosis, and orally inhaled ciclesonide was administered. At a 7-month follow up, the patient had improved clinically and radiologically. The outcome of this case indicates that immunohistochemical evaluation using a P. acnes antibody may be useful for diagnosing necrotizing granuloma.