Mrs TN is a 61-year-old woman from Gauteng Province in South Africa (SA). Informed consent was obtained from the patient. She is a patient with RA and at the time of presentation had been managed with disease-modifying anti-rheumatic drugs (DMARDs) including methotrexate and oral corticosteroids. In addition, she was enrolled in a biological therapeutic trial using a selective JAK1 inhibitor. She was not known to be HIV-infected and her known comorbid conditions included hypertension and dyslipidaemia. 
 She was initially admitted to hospital in May 2019 with a diagnosis of multi-lobar pneumonia, for which she received  empiric antibiotic therapy and was later discharged. Subsequent follow-up at the rheumatology clinic revealed worsening lung infiltrates, despite a lack of symptoms and clinical complaints. She was referred to the pulmonology clinic for further assessment, and her clinical examination was noted to be remarkably normal with an oxygen saturation of 93% on room air. Pulmonary function testing showed a post bronchodilator forced expiratory volume in 1 second to forced vital capacity ratio (FEV1 /FVC) of 0.79, total lung capacity of 4.78 L (109.26% of predicted) and a diffusion capacity for carbon monoxide per alveolar volume (DLCO/VA) of 0.34 nmol/ min/kPa/L (21% of predicted). The low DLCO may be due to a ventilation/perfusion  (V/Q) mismatch secondary to underlying lung disease. 
 Her initial chest radiograph from May 2019 showed 2 discrete solid lung nodules in the left mid to upper lung zones measuring 15 mm x 17 mm and 17 mm x 19 mm, respectively. In addition, the left lower zone revealed an ill-defined area of ground glass opacification (Fig. 1A). A repeat chest radiograph in July 2019 revealed that the lesions had increased in size (Fig. 1B).
A computed tomography (CT) scan of the chest revealed multiple, well defined, peripheral and patchy air space opacifications with airbronchograms involving the left lower lobe and abutting the oblique fissure. This was associated with pulmonary nodules and left pleural thickening (Figs 2A and B). Initial blood results revealed a C-reactive protein (CRP) of 5 mg/L, erythrocyte sedimentation rate (ESR) of 20 mm/hr and a normal full blood count. Sputum investigations were negative for tuberculosis.
 Metastases should be bilateral, and the evolution and doubling time is unlike malignancy. In addition, infections, pulmonary infarctions and vasculitic lesions could be considered, but the patient's normal CRP and ESR were not consistent with an acute inflammatory state. Owing to the peripheral nature of these lesions, she underwent a CT-guided transthoracic lung biopsy, which revealed fibrous connective tissue with evidence of chronic necrotising granulomatous inflammation and fungal organisms with the morphological features of Cryptococcus (Figs 3A and B).
Ziehl-Neelsen staining was negative for acid- and alcohol-fast bacilli. A diagnosis of pulmonary cryptococcosis was made. 
 The JAK1 inhibitor was discontinued and the patient was started on oral fluconazole at a dose of 400 mg 12-hourly for the duration  of 1 month. Follow-up chest radiography revealed partial resolution of the lesions noted previously (Fig. 4A).  Fluconazole 200 mg twice daily for 3 months and then 200 mg daily thereafter was continued. Subsequent repeat CT imaging done 6 months after initiation of therapy revealed resolution of lung nodules and masses, with some residual fibro-cavitary lung changes remaining in areas previously involved by mass formation (Fig. 4B). The patient has fortunately maintained a stable clinical condition and remains well, without deterioration of her lung functions and her RA has remained stable.