Tinea nigra palmaris-associated peritonitis, caused by Hortaea werneckii: The first case report in a peritoneal dialysis patient

We report the first case of peritoneal dialysis (PD) patients with peritonitis from Hortaea werneckii, a halotolerant black yeast-like fungus. The pathogen was confirmed by nucleotide sequences of internal transcribed spacer regions of the ribosomal RNA gene. A potential cause of this infection was tinea nigra on the patient's palm. Therefore, gloving might be advised during PD bag exchange in patients or caregivers who have an obvious lesion of the palm.

Interdigital Tinea Nigra

Tinea nigra is an uncommon superficial dermatomycosis precipitated by Hortaea werneckii, a halophilic and halothermic yeast-like fungus capable of producing a melanin-like substance. This pathogen infiltrates the stratum corneum in the setting of microtrauma and produces an asymptomatic brown to black macule or patch that appears similarly to melanocytic nevi or melanoma. We present a case of a 52-year-old woman who presented to clinic several months after developing a painless, nonpruritic dark brown patch in her left foot inside the fourth toe web. The coloration and location of this lesion would typically prompt biopsy; however, Wood's lamp examination and potassium hydroxide (KOH) preparation were pursued first and demonstrated evidence of infection by H. werneckii. The patient was treated with topical clotrimazole cream and miconazole powder for one month, and her lesions cleared completely. Her lesions did not recur at her three-month follow-up appointment.

Tinea nigra showing a parallel ridge pattern on dermoscopy

An 18-year-old healthy female student noticed a brown macule measuring 21 mm in diameter on the left palm and visited our clinic concerned about a cancerous mole. Dermoscopic examination revealed a brown, fine-dotted and granule-like structure overlapping an amorphous light brown macule. However, unlike previous cases, analysis of the high dynamic range-converted image revealed the parallel ridge pattern frequently observed in malignant melanomas. Brown mycelia were detected on direct microscopic examination; black colonies were isolated on fungal culture and the fungus was identified as Hortaea werneckii. The lesion was treated with topical ketoconazole cream, and it diminished 1 month later.

Palmar lichen planus mimicking tinea nigra

Lichen planus (LP) is a chronic inflammatory skin disease characterized by polygonal, violaceous papules commonly involving flexural areas of the wrists, legs, and oral and genital mucous membranes. This report describes a patient who presented with asymptomatic black colored patches on both palms simulating Tinea nigra, a superficial fungal infection. She was previously diagnosed as allergic contact dermatitis and was being treated with potent topical steroid i.e. clobetasol propionate 0.05% and white soft paraffin. Dermatoscopy of the lesion showed brownish pigmentation along ridges of the dermatoglyphics. A biopsy from the lesional skin showed findings of lichen planus. Our case highlights the potential diagnostic confusion that can occur with unusual variants of palmoplantar lichen planus and importance of histopathology in diagnosis of such unusual lesions.

Tinea nigra by Hortaea werneckii, a report of 22 cases from Mexico

Tinea nigra is a superficial mycosis caused by Hortaea werneckii. It is an infrequent asymptomatic infection that affects human palms and soles, and is mostly observed in tropical countries. We evaluate retrospectively twenty-two confirmed cases of tinea nigra from a total of eleven yr (1997–2007) and discuss the epidemiology, clinical features and treatment of this disease. In twelve cases, adults were involved, in 10, children. In nineteen cases the disorder was located on palms of hands and in three on soles of feet. In all cases, the obtained isolates were morphologically identified as Hortaea werneckii and the identification of ten isolates was retrospectively confirmed with the help of sequences of the internal transcribed spacer regions of the ribosomal DNA. The patients received topical treatment with Whitfield ointment, ketoconazole, bifonazole, or terbinafine. Treatment with keratolytic agents and topical antifungals was effective.