Plasma cell pneumonia induced by Legionella pneumophila.

We report a case of severe Legionella pneumonia in which the histopathologic features of an open lung biopsy specimen were characterized by a monotypic plasma cell infiltrate and absence of granulocytes or other acute inflammatory cells. The clinical course was otherwise typical for a severe case of Legionella pneumonia with complete functional and roentgenographic recovery following a prolonged convalescence. We speculate on possible reasons for this patient's unusual histopathologic features.