The frontal chest x-ray shows a thick-walled cavity in the left upper lobe with surrounding consolidation, which turned out to be due to a fungal infection.

A useful mnemonic for causes of lung cavity is  CAVITY (reference: radiopaedia)

C: cancer

A: autoimmune (e.g. Wegener’s granulomatosis, rheumatoid nodule)

V: vascular (e.g. pulmonary embolism)

I: infection (i.e. bacterial/fungal)

T: trauma (e.g. pneumotocele)

Y: youth associated (e.g. pulmonary sequestration)