An 81-year-old woman, with hypertension and dyslipidaemia, was admitted with an 8-month history of intermittent episodes of persistent cough, occasionally productive of yellowish sputum, and mild exertional dyspnoea, associated with malaise and 10 kg weight loss, but no fever or night sweats related. She was diagnosed as having chronic bronchitis and community-acquired pneumonia, receiving several courses of different empiric antibiotics, like amoxicillin and azithromycin with little improvement. On admission, she looks malnourished, weight 47 kg, body mass index 17 kg/m2, arterial pression 126/60 mm Hg, heart rate 78 per minute, respiratory rate 22 per minute and temperature 36.5°C. On physical examination, the only positive finding was diffuse wheezing and rhonchi, with bibasilar rales. A CT of the chest demonstrated multiple nodules of different sizes and diffuse distribution, some of them cavitated and with a pattern of 'tree-in-bud', associated with mediastinal lymphadenopathies, traction bronchiectasis in the middle lobe and lingula, and a left upper lobe consolidation (figures 1 and 2). A brochoalveolar lavage (BAL) was performed, showing multiple acid-fast bacilli, but molecular analysis ruled out tuberculosis (tuberculosis PCR), and finally Mycobacterium avium-intracellulare (MAI) grew on thin lay cultures. Based on her symptoms, on the findings of imaging studies and BAL culture, we arrived at the diagnosis of nontuberculous mycobacterial lung infection, specifically, Lady Windermere syndrome. She was started on three anti-MAI medications including azithromycin, ethambutol and rifampin, according to local guidelines, and slowly improve over weeks.