A mimic's imitator: a cavitary pneumonia in a myasthenic patient with history of tuberculosis.

A 77-year-old man with myasthenia gravis receiving prednisone and plasmapheresis was found to have right upper lobe cavitary pneumonia on radiological imaging studies after thymectomy. He had a remote history of treated pulmonary tuberculosis (TB) at the age of 19. On the basis of history of TB and current prednisone therapy, reactivation of pulmonary TB was highly suspected. Branching Gram-positive bacilli were identified on bronchoalveolar lavage (BAL). BAL Ziehl-Neelsen Acid-fast bacilli stain was negative, but a modified Kinyoun stain revealed branching, beaded, filamentous bacilli, suggestive of Nocardia spp. Nocardia cyriacigeorgica grew from the BAL culture. Cerebral MRI demonstrated a right frontal lobe lesion, clinically correlated to be nocardial brain abscess. The patient was treated with three-drug antimicrobial therapy (trimethoprim-sulfamethoxazole, meropenem, linezolid) for 2 months, followed by an additional 10 months of trimethoprim-sulfamethoxazole. Amikacin would have been included in the initial three-drug regimen, but its use was contraindicated in our myasthenic patient because aminoglycoside would trigger fatal myasthenic crisis by neuromuscular blockage. Follow-up imaging studies revealed resolution of the lung and brain lesions.