Misleading subcutaneous mycosis: a case report of subsequent clinical mycetoma-like and histological chromoblastomycosis-like lesions

Abstract

Hyalohyphomycosis and phaeohyphomycosis are groups of mycoses caused by several agents and show different clinical manifestations. We report a case of an immunocompromised patient who presented rare manifestations of opportunistic mycoses: mycetoma-like hyalohyphomycosis on his right foot caused by Colletotrichum gloeosporioides, followed by cutaneous phaeohyphomycosis on his right forearm caused by Exophiala oligosperma. Further to the rarity of this case, the patient's lesion on the foot shows that the clinical aspects of mycetomas could falsely appear in other fungal infections similar to hyalohyphomycosis. We also show that the muriform cells that were seen in the direct and anatomopathological examination of the skin are not pathognomonic of chromoblastomycosis, as observed in the lesion of the patient's forearm.

Figure 1. A) Tumor with lobulated surface and fistulous ostia, with drainage of serosanguineous material, without grains, located on the dorsum of the left foot; B) Magnetic resonance imaging depicting multiple septa and nodules affecting deep tissue planes, containing exudate, without bone involvement.

Figure 2. A) Direct examination of skin scrapings in Potassium Hydroxide (KOH) 20%, showing filamentous hyphae; B) Characteristic structures of the Colletotrichum gloeosporioides complex at 40× magnification.; C) Chronic granulomatous suppurative dermatitis presenting frequent filamentous fungal structures, without grains, observed in Hematoxylin-eosin staining at 400× magnification; D) Grocott's methenamine silver staining of sinus mucosal biopsy demonstrating diverse fungal elements, including broad, pauci-septate hyphae (5–10 µm), suggestive of mucormycosis, and thinner hyphae, mostly with right-angle branching, indicative of hyalohyphomycosis

Figure 3. A) Nodular lesion measuring 1.5 cm in diameter, located on the right upper forearm; B) Colonies of Exophiala oligosperma complex cultured on Saboraud Dextrose Agar after 2 months of growth; C) Muriform cells observed in Periodic acid–Schiff (PAS) staining at 400× magnification; D) Muriform cells observed in hematoxylin-eosin staining at 400× magnification.