Clin Case Rep. 2022 Nov 27;10(11):e6667. doi: 10.1002/ccr3.6667. eCollection 2022 Nov.
Some Aspergillus species produce oxalic acid, which reacts with tissue calcium or blood to precipitate calcium oxalate. Oxalate crystals can induce lung and kidney damage. The presence of oxalate crystals can suggest the diagnosis of aspergillosis, even when Aspergillus hyphae are absent on microscopic slides.