Chromomycosis is a chronic fungal infection disease that infects the subcutaneous tissue of the skin and also refers to as “Chronic subcutaneous mycosis”. It mainly occurs by the diverse group of dematiaceous or black fungi. Dematiaceous fungi are the heterogeneous group of fungi, which usually forms lesions or abscesses in the subcutaneous tissue. Interaction of host tissue with the fungus shows a non-specific kind of response. Macrophage and neutrophils play a significant role to create an immunological response against this disease.
Chromomycosis also refers as “Chromoblastomycosis” or “Phaeohyphomycosis”. Dematiaceous fungi include Fonsecaea pedrosoi, Phialophora verrucosa, Cladosporium carrionii which enters to the subcutaneous tissue via skin surface.
Causative Agent of Chromomycosis
Dematiaceous fungi are the aetiological agent which belongs to the phylum “Ascomycota” and order “Chaetothyriales”. Dematiaceous fungi undergo cell division “Meristematically” not through budding and cause “Septation” that infects the subcutaneous tissue.
The transmission of the fungus can occur by the “Autoinoculation” i.e. scratching of the infected site to the other parts. A group of dematiaceous fungi can present in soil, plants and plant debris. Thus, barefoot agriculture workers and woodcutters are more affected by this disease.
Chromomycosis mainly occurs in subtropical and tropical regions like Asia, America. Many cases result in Mexico, Cuba etc. Outside the American continents, a first case occurred in the year 1927. In Africa, most cases were reported in Madagascar and South Africa. In Asia, Chromomycosis is more prevalent in countries like Japan, SriLanka, India etc. Thus, the distribution of the disease is worldwide.
Chromomycosis is more prevalent in males having an age limit between 30-50years and those who are engaged in agricultural activities. A person with HLA-A 29 antigen is ten times more susceptible to this disease.
In males: Chromomycosis is prevalent in the upper limbs, buttocks and lower limbs.
In females: Chromomycosis is prevalent in the upper limbs, neck, face and lower limbs.
The most common feature of Chromomycosis is the appearance of Sclerotic lesions on the skin. The disease mainly affects the upper limbs, lower limbs and the buttock area.
Initial stage: Small red or grey bump appears during the initial stage and eventually warty dry nodule appears refers as “Primary lesions”. The formation of lesions is confined to the subcutaneous tissue of the feet and lower legs. The size and shape of the warty lesions can vary from person to person. The disease progresses very slowly and may take up to 10 years from the infection to the diagnosis. Based on the morphological features, a lesion can be of five types like:
It is the most common type of lesion, which occurs most frequently. Nodular type of lesion can distinguish by the following features:
- Colour of lesion: Pale pink in colour.
- The appearance of lesion: soft lesion with slightly raised papules.
- The surface of lesion: A surface of the lesion can be smooth, papillary and scaly.
- Further, many nodules transform into the tumoral lesion.
It can distinguish by the following features:
- The appearance of lesion: Appears as large, protruding papules.
- The surface of lesion: It is lobulated and covered with dirty grey epidermal remains.
- The shape of the lesion: Resembles the shape of Cauliflower.
- Size of lesion: Lesion forms tumoral masses which grow in size.
The appearance of hyperkeratotic lesions shows a sign of having verrucous chromomycosis that usually occurs in the upper or lower limbs. It most frequently affects the edges of the feet.
This type of lesion occurs very frequently with various shapes and sizes. The lesion forms are reddish to violet in colour with a scaly surface.
This forms rarely with the annular, arched lesions in the substantial areas of the body.
Based on the severity, Chromomycosis can classify into three types:
- Mild form: The condition is mild if a single nodule forms with a diameter greater than 5cm.
- Moderate form: The condition is moderate, if single or multiple nodules of tumoral, verrucous or plaque-type forms with a diameter greater than 15cm.
- Severe form: A condition is severe if the diameter of the lesion exceeds by covering the extensive skin areas.
The complications of Chromomycosis involves secondary infections and ulcerations. In severe cases, it leads to lymphoedema and ankylosis occurs. Chromomycosis results in swelling of limbs which leads to elephantitis. The lesions become carcinogenic which results in the development of squamous cell carcinoma. Fonsecaea pedrosoi also cause brain abscesses.
Chromomycosis can be diagnosed based on the presence of thick-walled, sclerotic muriform cells or medlar bodies from the skin scraping.
Culture method: A sample of the infected site can be cultured on the selective media like Sabouraud agar media (SDA) supplemented with cycloheximide. On standard media, Chromomycosis can be characterized by the slow growth of black colonies. For further assessment of the disease, the slide culture method is employed to determine the microscopic features.
Direct examination: The presence of sclerotic medlar bodies can be directly examined in the potassium hydroxide mounts. It results in the appearance of dark golden brown, sub-globose, multicellular, planate and dividing yeast cells of medlar bodies.
Other techniques: Techniques like biopsy and molecular methods confirm the diagnosis. Duplex PCR of ribosomal DNA helps in the diagnosis of Fonsecaea sp. and oligonucleotide primer diagnoses the presence of C. carrionii.
Chromomycosis can be treated by certain chemical and physical methods.
It includes treatment of Chromomycosis with antifungal agents like:
Itraconazole: Based on the severity of the disease, a daily dose of Itraconazole with 200-400 mg is generally recommended. In mild cases, a disease recovers within 6-12 months, but in severe cases takes several months. Itraconazole behaves as a “Fungistatic agent”, so there may a chance of relapsing of the disease.
Terbinafine: It is the antifungal agent which is recommended with a daily dose of 500-1000 mg.
Posaconazole: It is found effective with a dose of 800 mg/day.
5-Flourocytosine: It is not effective but usually recommended with a dose of 100-150mg/kg/day in four doses for 6-12 months.
It includes surgical excision, cryosurgery, thermotherapy and laser vaporisation.
Surgical excision: It is useful for the treatment of primary lesions that are limited in number, but not effective for the secondary lesions.
Cryosurgery: It involves the treatment of Chromomycosis with liquid nitrogen and is more effective with combination Itraconazole therapy. In cryosurgery, fungus removes within 1-2 weeks from the site of the lesion.
Thermotherapy: It makes the use of “Pocket warmers” which are allowed to place on the lesion site for 24hours a day. Thermotherapy is found to be effective in conjugation with antifungal chemotherapy.
Laser vaporisation: This method in combination with thermotherapy can successfully excise the sclerotic nodules. Laser vaporisation method used in Germany for the removal of buttock lesions.