Tinea Nigra

What is Tinea nigra?

It is a benign fungal skin disease affecting the exterior of the skin, and is characterized by pigmented macules – specifically on the palms. This disease occurs over a long period of time and its incubation time may be a few weeks or even more. Multiple or single macules with varied shapes are caused due to this infection, and mostly observed in children.

Tinea nigra Palmaris occurs on palms. The type of the infection occurring on the soles is classified as Tinea Nigra Plantaris. It is also known as Superficial phaeohyphomycosis.

Tinea nigra Incidence

It can be classified as a rare disease. The occurrence of the condition is primarily heavier in tropical humid climates experienced in the Caribbean, Asia, South and Central America besides the African shores. It has rarely been reported in UK and USA. Some sources suggest that the prevalence is greater in women and children, basically young individuals below 20 years of age.

Causes of Tinea nigra

The causative agent of this disease is Hortaea werneckii, a fungus which resides in soil, sewage, decomposed wood and manures in a humid climate. The disease gets transmitted by coming in direct contact with the fungus from these places. The fungus grows on the stratum corneum and does not go beyond it. It can easily stick to the outer skin layer due to lipophilic qualities. As found through studies, it may incubate for around 7 weeks. The longest reported incubation period spanned 20 years. This microbe thrives well on specific areas of the human skin which sweat much, as it is accustomed to live in surroundings with low pH and high salt concentrations.

Picture of Tinea Nigra

Picture 1 – Tinea Nigra

This fungus causes pigmentation on the palms due to the buildup of a substance similar to melanin in it. It is considered that minor cuts or trauma might pave the path for these fungi to cause this skin disease.

Tinea nigra Symptoms

The condition is predominantly asymptomatic. In rare conditions, however, it may cause Pruritus – a disorder that is characterized by slight burning or itching. Its occurrence may also be indicated by several other symptoms.

  • It is identified by the occurrence of black or brownish spots without scales having sharp borders. The spots might make one feel as if the skin has been stained with silver nitrate.
  • Macules may differ in their size, which may range between 1mm and 1.5 cm.
  • These occur on the palms. In very rare instances, feet may be involved.
  • The macules have an asymmetric, almost always unilateral presentation.

The condition is not accompanied by Erythema.

Tinea nigra Diagnosis

During initial investigation, the medical history of a patient is likely to be considered. A physician looks into the symptoms and carefully examines the discoloration. When physical exam is complete, other tests may be necessary (if deemed important by a physician). There is a possibility of misdiagnosing the symptoms of discoloration as malignant melanoma, a far serious disease that exhibits similar pattern. This often prompts doctors to perform Scotch tape test which can distinguish it from those serious ailments.  A skin sample may be taken and examined in the laboratory, where histopathological findings suggest the presence of the fungus which is responsible for it. Fungal growth is well-depicted through Dermatoscopy.

Tinea nigra Differential Diagnosis

The differential diagnosis of this disease may include confirming that a patient is not suffering from any other disorder (that produces similar symptoms) such as:

Image of Tinea Nigra

Picture 2 – Tinea Nigra Image

  • Melanoma
  • Melanocytic nevi
  • Addison’s disease
  • Pinta

Due to the rate at which it spreads, the disorder is often suspected as Syphilis (In some cases).

Treatment of Tinea nigra

The treatment of the disease basically consists of alleviating fungal infection. Antifungal agents are administered to eliminate the infection but often a long treatment is required to prevent it from coming back. It may take around 3 to 4 weeks approximately to get rid of it completely. Miconazole, salicylic acid and ketoconazole ointments and creams are usual treatment options. For removing the dark spots, topical keratolytic agents are applied or such scrubs are used on them. Treatment using itraconazole therapy has been reported. However, it is not the preferred means of cure.

Tinea nigra Prevention

It is better to refrain from venturing into places which may be infested with the H. Werneckii fungus. It would be wise to avoid sewage, dirt or rotten woods and fishes.

Tinea nigra Prognosis

The prognosis of this disease is extremely good as it is curable with proper treatment. It may take a few weeks for the infection to subside. The clinical signs diminish with administration of topical treatments and do not show a tendency to recur.

References:

http://dermatology-s10.cdlib.org/148/pearls/tinea_nigra/xavier.html

http://www.scribd.com/doc/29038405/3/Tinea-nigra

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2610305/

http://www.med.nyu.edu/content?ChunkIID=112174

http://emedicine.medscape.com/article/1092976-overview

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