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Phaeohyphomycosis caused by Rhinocladiella similis mimicking Sporotrichosis

Summary

A 34-year-old factory worker developed multiple nodules on his hand following an injury, initially suspected to be sporotrichosis, a common fungal infection. Through laboratory testing including fungal culture and genetic sequencing, doctors identified the actual cause as a rare fungus called Rhinocladiella similis. The patient was successfully treated with antifungal medication and showed gradual improvement. This is the first case of this fungal infection reported in India.

Background

Phaeohyphomycosis is a fungal infection caused by dematiaceous fungi. Rhinocladiella similis has been primarily reported from Brazil causing chromoblastomycosis. This case presents an unusual presentation mimicking sporotrichosis in a patient with history of mechanical trauma.

Objective

To describe a case of phaeohyphomycosis caused by Rhinocladiella similis presenting with clinical features simulating sporotrichosis and to highlight the diagnostic challenges in differentiating between these infections.

Results

Histopathology showed hyperkeratosis and papillomatosis without fungal structures. KOH mount revealed round yeast-like cells. Culture on Sabouraud’s dextrose agar produced white to grayish colonies turning greenish black, with LPCB mount showing thin hyaline septate hyphae and oval conidia in bottle brush pattern. ITS sequencing confirmed Rhinocladiella similis. Patient responded to itraconazole 200 mg twice daily for 12 weeks with gradual lesion regression.

Conclusion

This is the first reported case of R. similis phaeohyphomycosis from the Indian subcontinent. The case highlights the need for thorough evaluation to differentiate this infection from sporotrichosis and emphasizes the importance of studying the ecological niche and clinical spectrum of this pathogen.
  • Published in:Medical Mycology,
  • Study Type:Case Report,
  • Source: 10.1093/mmy/myac072.P265, PMID: PMC9509994
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