Pulmonary inflammatory pseudotumor is a rare lesion of the lung. It has been associated with EBV and HHV-8 but there not been a reported association with MAC infection.
A 64-year-old woman had a two-year history of chronic productive cough and weight loss unresponsive to two courses of treatment with a macrolide antibiotic. Chest radiographs over the initial three-month evaluation period revealed a persistent infiltrate in the superior segment of the right lower lobe, and a CT scan of the chest revealed consolidation of the superior segment of the right lower lobe and posterior segment of the right upper lobe. Transbronchial biopsy revealed a dense inflammatory infiltrate with collagen fibrosis, proliferation of lymphocytes and plasma cells consistent with inflammatory pseudotumor. Culture of the specimen revealed numerous MAC organisms. Surgical resection was recommended, but the patient refused. She was started on rifabutin, ethambutol, and clarithromycin, with intention to reevaluate after 3 months for surgical removal of the pseudotumor. The patient was lost to follow up for 10 months; on return, she stated that her cough had resolved while on the antibiotics, which she stopped taking after 3 months. Following discontinuation of the antibiotics symptoms recurred. A follow-up CT scan of the chest revealed a decrease in the size of the previous right lung opacity. Surgery was again advised, and she was again lost to follow-up for six months. At the time of the last admission, she was a thin, diaphoretic woman using accessory muscles of respiration. The pulse was 153/min, blood pressure of 118/78 mm Hg, respiratory rate 40/min, and temperature of 39°C. Pulse oximetry showed an oxygen saturation of 84% breathing room air. Coarse inspiratory rales were present bilaterally. A chest radiograph revealed dense opacification of the right lung field, sparing the apex, associated with shift of the mediastinum to the left. CT scan revealed a large right lower lobe mass, with complete collapse of the right lower and middle lobes. A moderate pleural effusion was present.The patient was admitted to the medical intensive care unit and started on moxifloxacin for presumed pneumonia. On hospital day 2, endotracheal intubation and flexible bronchoscopy were performed, revealing obstruction of the right lower lobe superior segment and medial basal segment bronchi by pearly white material that did not clear with suctioning. Biopsy of one of those lesions showed inflammatory cells. Methylprednisolone, 40 mg IV every 6 hours was started. Over the next few days, oxygenation and the radiographic abnormalities improved. She had a right thoracotomy on day 11, revealing for a large mass invading all three lobes of the right lung. The mass was enucleated (along with a portion of the chest wall), and the histology was consistent with an inflammatory pseudotumor. Giant cell granulomata with necrosis were also noted. Cultures of the lesion were MAC, and azithromycin, amikacin, rifampin and ethambutol were begun. After 50 days in the hospital, the patient was removed from the ventilator and discharged to a subacute rehabilitation unit. She was maintained on MAC treatment with complete resolution of symptoms and the radiographic abnormalities.
Inflammatory pseudotumor is a rare lesion of unknown etiology, characterized by proliferation of lymphocytes, plasma cells, neutrophils and fibroblasts forming mass lesions. Some cases have been confused with malignancy. In our case, the persistent positive cultures for MAC and the initial regression on antimicrobial treatment suggests that MAC infection was related to the development of the pseudotumor.
To our knowledge this is the first case of inflammatory pseudotumor associated with MAC infection.
Vanessa Ribaudo, None.