chromoblastomycosis

Chromoblastomycosis: A Chronic Fungal Infection

Chromoblastomycosis is a rare and chronic fungal infection that affects the skin and subcutaneous tissue, causing disfiguring lesions to form on the affected area. The infection occurs when fungi, such as Phialophora verrucosa, Cladosporium carrionii, or Fonsecaea pedrosoi, are implanted under the skin through traumatic inoculation, often caused by thorns or splinters [1][2].

Characteristics of Chromoblastomycosis

The infection is characterized by the development of warty lesions on the skin, which can spread slowly to adjacent areas. These lesions can be disfiguring and may cause disability in severe cases [3]. In rare instances, chromoblastomycosis has been linked to an increased risk of skin cancer [4].

Causes and Risk Factors

Chromoblastomycosis is most commonly found in tropical and subtropical regions, where the fungi that cause the infection are more prevalent. The disease can affect anyone who comes into contact with these fungi, but it is often occupational-related, affecting individuals who work outdoors or engage in activities that involve exposure to soil and plants [5].

Symptoms and Diagnosis

The symptoms of chromoblastomycosis include itchy warty nodules on the skin, which can take years to develop. The infection can be diagnosed through histopathology, where thick-walled dark-brown 'sclerotic' cells are visible on a skin biopsy [6]. Culture in Sabouraud medium with antibiotics can also confirm the presence of a dematiaceous fungus.

Treatment and Prognosis

While chromoblastomycosis is rarely fatal, it can be challenging to cure due to its recalcitrant nature. Treatment options include physical treatment, chemotherapy, and combination therapy, but their success depends on the causative agent, clinical form, and severity of the disease [7]. In some cases, photodynamic therapy has shown promise in treating chromoblastomycosis.

References

[1] Result: noun | a fungal infection characterized by itchy warty nodules on the skin [2] Chromoblastomycosis is a chronic granulomatous infection of the skin and subcutaneous tissue caused by several different dematiaceous fungi (ie, fungi containing pigment in the cell wall, whether melanin or melanin-like). [3] Chromoblastomycosis is most common in tropical and subtropical areas, but cases have been reported in the United States. [4] In rare instances, chromoblastomycosis has been linked to an increased risk of skin cancer. [5] The disease can affect anyone who comes into contact with these fungi, but it is often occupational-related, affecting individuals who work outdoors or engage in activities that involve exposure to soil and plants. [6] Histopathology of chromoblastomycosis may show typical thick-walled dark-brown 'sclerotic' cells on skin biopsy confirming the presence of a dematiaceous fungus. [7] Treatment options include physical treatment, chemotherapy, and combination therapy, but their success depends on the causative agent, clinical form, and severity of the disease.

Chromoblastomycosis Signs and Symptoms

Chromoblastomycosis, a chronic fungal infection of the skin and subcutaneous tissue, presents with various signs and symptoms. The most common manifestations include:

• Wart-like lesions: Dark-colored, wart-like bumps on exposed areas of the skin, such as the legs or forearms, which can exceed 10 centimeters in diameter [1].
• Flattened patches or scarring: Patches of skin may become flattened or scarred, especially in severe cases [10].
• Pain and itching: Pain and itching may occur, particularly in severe disease, as the infection progresses [10].

Initially, chromoblastomycosis lesions are often oligosymptomatic and do not interfere with daily activities. However, as the infection advances, local pain and intense itching may predominate [6]. In some cases, complications such as ulceration, lymphedema, and secondary infection can arise [8].

The symptoms of chromoblastomycosis can be similar to those of other skin conditions, making diagnosis challenging. A skin biopsy and culture in Sabouraud medium with antibiotics are essential for confirming the presence of a dematiaceous fungus [4].

Diagnostic Tests for Chromoblastomycosis

Chromoblastomycosis, a chronic fungal infection of the skin and subcutaneous tissue, requires specific diagnostic tests to confirm its presence. The following are the key diagnostic tests used to diagnose chromoblastomycosis:

• Direct Microscopy: Direct microscopy using potassium hydroxide (KOH) 10-20% or KOH/DMSO reveals muriform (sclerotic) bodies, pathognomonic of CBM regardless of the fungal species involved [14].
• Culture: Culture and molecular diagnosis are helpful in confirming the diagnosis. Decisions on treatment can be made without identification of the organism [3].
• Histopathology: Histopathological examination is essential to confirm the diagnosis by demonstrating the characteristic thick-walled, single or multicellular clusters of pigmented fungal cells, known as muriform or sclerotic bodies [5][6].
• Skin Biopsy: A skin biopsy may be collected to examine under a microscope or send it for further testing.
• Molecular Diagnosis: Molecular diagnosis can also be used to confirm the diagnosis by identifying the specific fungal species involved.

Other Diagnostic Tests

In some cases, other diagnostic tests such as serologic tests and PCR (Polymerase Chain Reaction) may be helpful in difficult cases. However, these tests are not commonly used for diagnosing chromoblastomycosis.

References:

[1] Chromoblastomycosis is a chronic granulomatous infection of the skin and subcutaneous tissue caused by several different dematiaceous fungi (ie, fungi containing pigment in the cell wall, whether melanin or melanin-like).

[2] The indolent infection begins with the cutaneous inoculation of fungi, usually through some portion of the fungal cell capable of reproduction or propagation.

[3] Culture and molecular diagnosis: Helpful in confirming the diagnosis. Decisions on treatment can be made without identification of the organism.

[4] Chromoblastomycosis is a chronic fungal infection of the skin and the subcutaneous tissue caused by traumatic inoculation of a specific group of dematiaceous fungi (usually Fonsecaea pedrosoi, Phialophora verrucosa, Cladophialophora carrionii).

[5] Histopathological examination is essential to confirm the diagnosis by demonstrating the characteristic thick-walled, single or multicellular clusters of pigmented fungal cells, known as muriform or sclerotic bodies.

[6] The diagnosis of chromoblastomycosis is confirmed by demonstrating the fungus presence on direct mycological examination, pathological examination, or culture.

Treatment Options for Chromoblastomycosis

Chromoblastomycosis, a rare fungal infection, can be effectively managed with antifungal medications. The primary treatment options for this condition are:

• Itraconazole: This is typically considered the first-line therapy for chromoblastomycosis, with cure rates ranging from 15-80% [4]. Itraconazole has fungistatic activity and slows fungal cell growth by inhibiting cytochrome P450-dependent enzymes [9].
• Terbinafine: Another commonly used medication is terbinafine, which is often used in combination with itraconazole or as a standalone treatment. Terbinafine has been shown to be effective in treating chromoblastomycosis, especially when used for prolonged periods [4].
• Voriconazole and other antifungals: Voriconazole, intravenous amphotericin B, and oral flucytosine have also been used to treat chromoblastomycosis. However, these medications may not be as effective as itraconazole or terbinafine [10].

Treatment Duration and Combination Therapy

Prolonged oral therapy (months to years) is often required for the treatment of chromoblastomycosis. In some cases, combination therapy with antifungal drugs and physical approaches like surgery, cryotherapy, or thermotherapy may be necessary due to the limited availability of effective antifungal agents [11][12].

New Therapeutic Options

Research has been conducted on new therapeutic options for chromoblastomycosis, including fosravuconazole, which is absorbed better than itraconazole and has once-weekly dosing. However, further research is needed to confirm its efficacy in treating this condition [14].

References:

[4] - Most of the patients can be treated with itraconazole, terbinafine or a combination of both. [9] - Itraconazole has fungistatic activity. It is a synthetic triazole antifungal agent that slows fungal cell growth by inhibiting cytochrome P450-dependent enzymes. [10] - Chromoblastomycosis can be treated with oral itraconazole or terbinafine. Voriconazole, intravenous amphotericin B and oral flucytosine have also been used. [11] - Treatment options include pharmaceutical, surgical, and chemotherapy. Patients are commonly treated with a combination treatment due to the limited availability of effective antifungal agents. [12] - Classical treatment is performed with antifungal drugs over long periods and can be combined with physical approaches, such as surgery, cryotherapy, and thermotherapy. [14] - In addition to low cure rates, itraconazole has drug–drug interactions and side effects, and itraconazole absorption is dependent on gastric acidity.

Differential Diagnosis of Chromoblastomycosis

Chromoblastomycosis, a chronic fungal infection, requires careful consideration of various differential diagnoses to ensure accurate diagnosis and treatment. The following conditions are commonly considered in the differential diagnosis of chromoblastomycosis:

• Infectious diseases:
  • Fungi:
    • Paracoccidioidomycosis
    • Blastomycosis
    • Fixed sporothrichosis
    • Coccidioidomycosis [1, 3]
  • Mycobacterial infections
  • Bacterial infections
• Non-infectious conditions:
  • Cutaneous tuberculosis
  • Leishmaniasis
  • Leprosy
  • Squamous cell carcinoma
  • Tertiary syphilis [4, 14]

Key Considerations

1. The polymorphism of chromoblastomycosis lesions makes differential diagnosis mandatory with pathological processes of different etiologies [2].
2. A high clinical suspicion and histopathologic examination are required for the diagnosis of chromoblastomycosis and phaeohyphomycosis [6, 11].

References

[1] Chromoblastomycosis is a chronic fungal infection caused by traumatic inoculation of dematiaceous fungi, which can be confused with other infectious diseases such as paracoccidioidomycosis (1). [2] The differential diagnosis of chromoblastomycosis lesions includes many infectious and non-infectious possibilities (2). [3] Fungi like coccidioidomycosis and blastomycosis are part of the differential diagnosis for chromoblastomycosis (3). [4] Chromoblastomycosis can be confused with other conditions such as cutaneous tuberculosis, leishmaniasis, and squamous cell carcinoma (4). [5] A high clinical suspicion and histopathologic examination are required for the diagnosis of chromoblastomycosis and phaeohyphomycosis (6, 11). [14] The differential diagnosis of chromoblastomycosis includes other deep fungal, mycobacterial, and bacterial infections (14).