eMedicine Specialties > Dermatology > Fungal Infections

Tinea Nigra

Author: Robert A Schwartz, MD, MPH, Professor and Head of Dermatology, Professor of Medicine, Professor of Pediatrics, Professor of Pathology, Professor of Preventive Medicine and Community Health, UMDNJ-New Jersey Medical School
Coauthor(s): George Kihiczak, MD, Clinical Associate Professor, Department of Dermatology, New Jersey Medical School and University Hospital
Contributor Information and Disclosures

Updated: Sep 29, 2008

Introduction

Background

Tinea nigra is an uncommon superficial dermatomycosis usually caused by Hortaea werneckii, formerly known as Phaeoannellomyces werneckii, (formerly classified as Exophiala werneckii and Cladosporium werneckii).¹ It may also be due to Stenella araguata, first described and named Cladosporium castellanii in 1973.² This infection appears as a hyperpigmented macule, which usually occurs on the palms. The soles and, more rarely, other areas of the body, can also be affected.

Cequeira first described tinea nigra in 1891, calling the infection keratomycosis nigricans palmaris. In 1921, Horta isolated the pathogen and gave it its original name, C werneckii.

Although P werneckii has been established as the causative fungus in most cases of tinea nigra, other species of dematiaceous fungi, such as S araguata, may produce a similar clinical picture.

Two Medscape CME courses of possible interest are Fungal Skin and Nail Infections: Practical Advice for Advanced Practice Clinicians and Selecting Effective Treatment in the Antibiotic-Resistant Emergency Room Patient.

Pathophysiology

Tinea nigra is a superficial mycosis of the stratum corneum. Infection is believed to occur as a result of inoculation from a contamination source such as soil, sewage, wood, or compost subsequent to trauma in the affected area.

Typically, the incubation period is 2-7 weeks, although in experimental inoculation, the incubation period was 20 years.³ The fungus exhibits lipophilic adhesion to human skin; it is exclusively found in the stratum corneum and does not extend into the stratum lucidum.

P werneckii receives nourishment from its use of decomposed lipids. Its tolerance to an environment with a high salt concentration and a low pH allows the fungus to thrive in human skin. It has been isolated from the hypersaline waters of salterns as one of the predominant species of a group of halophilic and halotolerant melanized yeastlike fungi.⁴ P werneckii has distinct mechanisms of adaptation to high-salinity environments that are not seen in salt-sensitive and only moderately salt – tolerant fungi.

A pigmentary change in the skin results in a dark-colored macule due to the accumulation of a melaninlike substance in the fungus.

Frequency

United States

Tinea nigra is relatively uncommon in the United States. However, numerous cases are reported in the dermatologic literature. Tinea nigra typically affects people who reside in the coastal states such as Florida, Texas, Alabama, Louisiana, Virginia, and North Carolina. Although cases of tinea nigra are also reported in patients from northern and inland regions of the United States, including New York City, Chicago, and Boston, patients often report a history of foreign travel, frequently to the Caribbean islands.

International

Tinea nigra is not uncommon in tropical regions of Central America, South America, Africa, and Asia. Epidemiologic studies of skin diseases in schoolchildren performed by direct inspection using dermatologists in Magong, Penghu, Republic of China on the island of Formosa found the prevalence of fungal infection, including tinea nigra, tinea versicolor, and tinea corporis, to be 0.24% (95% confidence interval, 0.07-0.41%).⁵

Mortality/Morbidity

Although the fungal infection may be alarming because of its uncommon occurrence and its potential confusion with a more serious medical disorder (eg, malignant melanoma^6,7 ), tinea nigra is a benign disease that is easily curable.

Race

Tinea nigra appears to occur less often in the black population than in others, although this observation may reflect impaired recognition of the disease.

Sex

The female-to-male predilection is 3:1.

Age

Tinea nigra most often occurs in pediatric and adolescent populations; however, individuals of any age may be affected. In a study of 12 patients in Venezuela, it was found to be more prevalent among young people with fair skin aged 3-28 years who visited beaches.²

Clinical

History

• Generally, patients are asymptomatic.
• Rarely, pruritus may be reported.
• The absence of any discomfort often delays the patient's decision to seek medical advice.
• Patients who live in the inland areas of the United States generally report a history of foreign travel, most often to the Caribbean islands.
  • In addition, patients may have acquired this infection while visiting the tropical regions of Asia or Africa.
  • Those who reside in the coastal regions do not necessarily report any travel outside of the United States.
• Uezato et al⁸ reported a case of tinea nigra palmaris from Okinawa, Japan on the left palm of a 13-year-old girl, who had noticed the pigmented, asymptomatic macule on her left palm approximately 4-5 years prior to presentation. She stated the lesion became lighter after a bath and darkened some time later.
  • Physical examination revealed a 4 X 5-cm, dark brown, and irregularly shaped macule.
  • Histological findings were reported as follows: "Direct potassium hydroxide (KOH) microscopic examination from skin scrapings revealed branched brown hyphae with light brown septa. A fungal culture on Sabouraud's agar media produced wet, medium brown, yeast-like colonies, the surface of which later became black and shiny. A slide culture disclosed light brown, elliptic or peanut-shaped conidia comprised of one to two ampullaceous cells. Scanning electron microscopic examination of the conidia showed both annellation [sic] conidia with lunate bud scars and sympodial conidiogenesis."
  • DNA was extracted from separately cultured fungi, and polymerase chain reaction with primers specific to H werneckii was performed; results showed positive bands. Direct sequencing was performed with the DNA segments from the positive bands.
  • Type C H werneckii was determined to be the causative fungus, based on the base sequences obtained, and tinea nigra due to H werneckii was diagnosed.

Physical

Tinea nigra is characterized by the presence of a painless brown-to-black macule. The macule appears insidiously as a small dark spot.

• Hyperpigmentation of the macule ranges from light brown to black discoloration, resembling silver nitrate or India ink stains.
  • The borders are typically discrete.
  • The pigmentary change may appear mottled or velvety.
• The lesions are typically solitary, although more than one lesion can be present.
  • Solitary lesions are typically located on the palmar surfaces of the hands or plantar surfaces of the feet, and they may extend to the fingers or toes, respectively.
  • Other areas of the body, such as the neck and chest wall, are more rarely affected.
• The shape of the lesion varies, and they may appear ovoid, round, or irregular.
  • The lesion slowly grows over weeks to months.
  • The size may range from a few millimeters to several centimeters in diameter, depending on the duration of the infection.
• Other physical findings, such as erythema or induration, are absent.
• Rarely, scaling is present.
• Dermoscopic examination may facilitate the in vivo diagnosis of tinea nigra.⁹

Causes

• Tinea nigra is due to infection by the fungus, P werneckii, which is classified in the family Dematiaceae, class Hyphomycetes, phylum Deuteromycota.
• Infection occurs after inoculation subsequent to trauma.
• The dermatomycosis tends to occur in areas with an increased concentration of eccrine sweat glands.
• Hyperhidrosis appears to be a risk factor for this disease.

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