Chromoblastomycosis

How chromoblastomycosis develops

The fungi that cause chromoblastomycosis live in soil, rotting wood, thorny plants and plant debris. They are introduced into the skin through minor injuries: thorns, wood splinters, cuts from tools, or walking barefoot. Many people do not remember the injury because the infection develops slowly over months to years.

In the skin, the fungi form characteristic thick-walled, brown, multi-chambered cells called sclerotic bodies (also called muriform cells or "copper pennies"). These are very resistant to the immune system, which explains why the infection persists.

Chromoblastomycosis does not spread from person to person.

Where it occurs

It is found worldwide but is most common in tropical and subtropical regions, including:

• parts of Brazil and Latin America
• Madagascar and other parts of Africa
• parts of Asia, including India, China and Japan
• northern Australia

It is recognized by the World Health Organization as a neglected tropical disease. Cases in the US and Europe are rare and usually linked to travel or gardening exposure.

Symptoms

• A small, painless, pink or red bump or scaly patch at the site of injury
• Slow growth over months to years into raised, warty, crusted or cauliflower-like plaques
• Black dots on the surface, which are where the fungus is being pushed out of the skin
• Itching, which is common and can spread the infection to nearby skin by scratching
• Usually on the feet, legs or hands; less often the arms, trunk or face
• Little or no pain unless secondary infection develops

Lesions are classified as nodular, tumorous (cauliflower-like), verrucous (warty), scarring or plaque types.

Complications

• Secondary bacterial infection, causing pain, odor and discharge
• Lymphedema: chronic swelling of the leg from scarring of lymph vessels, sometimes severe ("elephantiasis")
• Spread to nearby skin by scratching or through lymph vessels
• Squamous cell carcinoma: rarely, cancer develops in long-standing lesions
• Disability from large lesions limiting walking or work

Diagnosis

Chromoblastomycosis can look like other chronic skin conditions, including sporotrichosis, mycetoma, cutaneous leishmaniasis, skin tuberculosis, psoriasis and squamous cell carcinoma. Diagnosis is confirmed by:

• Direct microscopy: scrapings from the black dots, treated with potassium hydroxide, show the brown sclerotic bodies, which are diagnostic.
• Skin biopsy: shows sclerotic bodies in the tissue with a characteristic inflammatory pattern.
• Fungal culture: identifies the species, which can guide treatment. Growth takes weeks.
• Molecular tests (PCR) in specialized labs.

Treatment

Treatment depends on the size and duration of the lesions. Cure rates are best for small, early lesions.

Small lesions

• Surgical excision with a margin of healthy skin, usually combined with antifungal tablets to prevent recurrence
• Cryotherapy (freezing with liquid nitrogen), often repeated
• Heat therapy or laser treatment in some centers

Larger or extensive disease

• Itraconazole tablets for many months, often 6 to 12 months or longer, until lesions clear
• Terbinafine is an alternative or can be combined with itraconazole
• Posaconazole for difficult cases
• Combination therapy with antifungals plus cryotherapy or surgery gives better results than either alone

Treatment is long, and relapse is common in advanced disease, so follow-up continues after lesions heal.

Prevention

• Wear shoes, gloves and protective clothing when working with soil, wood and plants
• Clean and cover minor cuts and puncture wounds promptly
• Seek early medical review for slowly growing skin lesions in endemic areas

Frequently asked questions

What causes chromoblastomycosis?

It is caused by dark-pigmented fungi that live in soil, wood and plants. They enter the skin through minor injuries such as thorn pricks or splinters. Farmers and others who work barefoot or with plants in tropical regions are most at risk.

What does chromoblastomycosis look like?

It starts as a small bump or scaly patch that slowly grows into raised, warty, crusted plaques, often with tiny black dots on the surface. It usually affects one leg or foot and can look like warts, psoriasis or other skin infections.

Is chromoblastomycosis contagious?

No. It does not spread from person to person. People catch it from the environment through skin injuries. It can, however, spread to nearby skin on the same person through scratching.

Can chromoblastomycosis be cured?

Small, early lesions can often be cured with surgery, freezing or antifungal medicine. Large, long-standing lesions are harder to treat and may need many months of antifungals combined with other treatments, and they can come back.

How long does treatment take?

Antifungal treatment usually lasts at least 6 to 12 months and sometimes longer, continuing until the lesions have cleared and tests no longer show the fungus. Regular follow-up is important to catch recurrence early.