Hendersonula toruloidea and Scytalidium hyalinum. Review and update

Hendersonula toruloidea and Scytalidium hyalinum are opportunistic organisms that can produce tinea pedis, tinea manuum, and tinea unguium. These infections, which clinically mimic those caused by dermatophytes but are caused by nondermatophyte agents, are correctly called dermatomycoses. When examined microscopically with potassium hydroxide, the agents of these disorders resemble those of dermatophytosis, showing narrow, septate, branching hyphae. It, therefore, becomes important to culture samples taken from sites with these tineas on cycloheximide-free agars even if they are potassium hydroxide-positive to rule out nondermatophyte mycoses. Correct identification becomes imperative since neither H toruloidea nor S hyalinum responds to conventional therapy. We review these diseases with emphasis on clinical appearance and differentiation from dermatophytosis. We also report four cases of S hyalinum infection of the nail or feet.