Pathologic features of
Mycoplasma pneumoniae infection (M.
pneumonia) are generally non-specific, and the literature regarding the pathologic features of M.
pneumonia with intraalveolar exudates is limited. Clinical and histopathological studies were performed in 3 patients with M.
pneumonia which did not respond to
erythromycin and
minocycline, but all rapidly recovered after
corticosteroid therapy. In pathologic findings, we observed intraalveolar exudates and focal organization in M.
pneumonia, and its intraalveolar lesions were compared between M.
pneumonia and
bronchiolitis obliterans organizing pneumonia containing
fibrin (BOOP). Immunohistochemical studies were performed using the
streptavidin biotin peroxidase complex method with anti-alpha-smooth muscle actin antibody and anti-pancytokeratin AE1/AE3 antibody. In pathologic findings, more
fibrin deposits in intaalveolar lesions were observed in M.
pneumonia than in BOOP. In intaalveolar lesions of M.
pneumonia, a larger amount of nuclear debris, more neutrophils, and more erythrocytes were noted. Myofibroblasts were observed in the organization of BOOP, while in the intaalveolar lesions of M.
pneumonia, myofibroblasts were not observed. These results suggest that M.
pneumonia with intraalveolar exudates responds well to
corticosteroid and its intraalveolar lesions apparently differed from those in BOOP.