Answer: Phaeohyphomycosis caused by Exophiala oligosperma. The mold was identified as Exophiala oligosperma (a member of the Exophiala jeanselmei complex) based on sequencing of the internal transcribed spacer (ITS). Amplification of the ITS region was performed using previously described fungus-specific primers ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′) and ITS4 (5′-TCCTCCGCTTATTGATATGC-3′) (1). Sanger sequencing indicated 100% match by BLAST with Exophiala oligosperma. The E. jeanselmei complex consists of dematiaceous saprobic fungi (2). In addition to E. oligosperma and E. jeanselmei, they include species such as E. heteromorpha, E. lecanii-corni, and E. xenobiotica (3). These fungi are very similar morphologically and are largely separated by molecular differentiation. Identification of Exophiala spp. to the species level may not be necessary due to similar ranges of clinical infections, with the exception of Exophiala dermatitidis (4–6). E. dermatitidis is neutroropic, with a propensity for causing cerebral phaeohyphomycosis. Other Exophiala spp. can cause infections particularly in immunocompromised people, commonly through direct inoculation (4), causing inflammation in the subcutaneous and cutaneous tissues and the formation of mycetoma, a chronic inflammatory granulomatous disease. The infection may potentially disseminate systemically and lead to arthritis and endocarditis in immunocompromised patients (4, 5). E. jeanselmei complex grows optimally at 30°C. Isolates from humans can grow at 37°C but are inhibited at 40°C. This evolutionary adaptation helped the complex’s survival on human hosts. Inhibition at 40°C and in 15% salinity, with growth in the presence of cycloheximide, is useful in differentiating E. jeanselmei complex from similar molds, such as Exophiala dermatitidis and Hortaea werneckii. Exophiala dermatitidis can grow at 40°C (7), while Hortaea werneckii is inhibited by cycloheximide and is able to grow in 15% saline. Use of matrix-assisted laser desorption–ionization time of flight mass spectrometry (MALDI-TOF MS) may also be considered for accurate identification. However, this is dependent on the availability of a reliable database (5). Torulose hyphae (see Fig. 1B and C in the photo quiz) are present in Exophiala spp. but may appear yeast-like on histological samples. Staining of melanin with the Fontana-Masson stain was not performed in our case but may be considered and could help differentiate dematiaceous molds from Candida spp. Dematiaceous molds appear pigmented on culture because of melanin in their cell walls. The melanin acts as a virulence factor via its scavenging effect on free radicals and hypochlorite, which are produced by phagocytic cells, and via binding to hydrolytic enzymes (8).