Alternaria alternata is a fungus most people have inhaled without knowing it. It drifts through outdoor air, coats decaying leaves, and is best known to agricultural scientists as a plant pathogen. In medicine it mostly shows up as an allergen and, occasionally, as an opportunistic infection in people whose immune systems are suppressed.
Spanish clinicians have now reported finding it in the toenails of a 50-year-old man whose immune system was working perfectly well. The case appeared in August in SN Comprehensive Clinical Medicine.
