A Case of Black Fungal Keratitis Caused by Biatriospora mackinnonii

To report a novel case of fungal keratitis caused by Biatriospora mackinnonii (Pyrenochaeta mackinnonii), a dematiaceous fungus (black fungus) that rarely causes dermatological infection, in a patient treated for ocular cicatricial pemphigoid.

An 81-year-old patient with ocular cicatricial pemphigoid was referred to our hospital because of persistent corneal epithelial defects in his left eye. On examination, a slightly elevated dark lesion in the middle of the erosion and hypopyon was observed in that eye, with smear examination of the obtained specimen revealed a filamentous fungal-like material. Initially, treatment included miconazole and fluconazole ophthalmic solution eye drops, natamycin ophthalmic ointment, and systemic voriconazole, followed surgical scraping of the mass, an anterior chamber lavage, and a subconjunctival injection of miconazole. However, the focus had resistance to the treatment and finally led to corneal perforation; hence, therapeutic penetrating keratoplasty (PKP) was subsequently performed.

Mycological testing revealed that the lesions were Candida parapsiliosis and black fungus, with the black fungus classified as B. mackinnonii via DNA sequencing of the internal transcribed spacer and the D1/D2 domains of the 28S rRNA gene. Fungal keratitis caused by B. mackinnonii was resistant to the antifungal drugs, yet was ameliorated by PKP, with no recurrence of fungal keratitis for more than 2 years postoperative.

To the best of our knowledge, this is the first reported case of fungal keratitis caused by B. mackinnonii; however, in this case, PKP surgery resulted in a favorable outcome.