Chromoblastomycosis
Encyclopedia
Chromoblastomycosis is a long-term fungal infection
of the skin and subcutaneous tissue (a chronic
subcutaneous mycosis). The infection occurs most commonly in tropical or subtropical climates, often in rural areas. It can be caused by many different type of fungi which become implanted under the skin
, often by thorns or splinters. Chromoblastomycosis spreads very slowly; it is rarely fatal and usually has a good prognosis
, but it can be very difficult to cure. There are several treatment options, including medication and surgery.
(skin elevation) appears. The lesion is usually not painful and there are few, if any symptoms. Patients rarely seek medical care at this point.
Several complications may occur. Usually, the infection slowly spreads to the surrounding tissue while still remaining localized to the area around the original wound. However, sometimes the fungi may spread through the blood vessels or lymph vessels
, producing metastatic lesions at distant sites. Another possibility is secondary infection with bacteria
. This may lead to lymph stasis (obstruction of the lymph vessels) and elephantiasis
. The nodules may become ulcerated, or multiple nodules may grow and coalesce, affecting a large area of a limb.
(KOH), then examine under a microscope. (KOH scrapings are commonly used to examine fungal infections.) The pathognomonic
finding is observing Medlar bodies, sclerotic cells. Scrapings from the lesion can also be cultured
to identify the organism involved. Blood tests and imaging studies are not commonly used.
On histology, chromoblastomycosis manifests as pigmented yeasts resembling "copper pennies." Special stains, such as periodic acid schiff and Gömöri methenamine silver, can be used to demonstrate the fungal organisms if needed.
Over months to years, an erythematous papule appears at the site of inoculation. Although the mycosis slowly spreads, it usually remains localized to the skin and subcutaneous tissue. Hematogenous and/or lymphatic spread may occur. Multiple nodules may appear on the same limb, sometimes coalescing into a large plaque. Secondary bacterial infection may occur, sometimes inducing lymphatic obstruction. The central portion of the lesion may heal, producing a scar, or it may ulcerate.
Other treatment options are the antifungal drug terbinafine
, an experimental drug posaconazole
, and heat therapy
.
Antibiotics may be used to treat bacterial superinfections.
Amphotericin B
has also been used.
, and secondary bacterial infection. There have been a few cases reported of malignant
transformation to squamous cell carcinoma
. Chromoblastomycosis is very rarely fatal.
areas and occurrence of chromoblastomycosis on the foot.
. Madagascar
and Japan
have the highest incidence. Over two thirds of patients are male
, and usually between the ages of thirty and fifty. A correlation with HLA
-A29 suggests that genetic factors may play a role as well.
Mycosis
A mycosis is a fungal infection of animals, including humans. Mycoses are common, and a variety of environmental and physiological conditions can contribute to the development of fungal diseases...
of the skin and subcutaneous tissue (a chronic
Chronic (medicine)
A chronic disease is a disease or other human health condition that is persistent or long-lasting in nature. The term chronic is usually applied when the course of the disease lasts for more than three months. Common chronic diseases include asthma, cancer, diabetes and HIV/AIDS.In medicine, the...
subcutaneous mycosis). The infection occurs most commonly in tropical or subtropical climates, often in rural areas. It can be caused by many different type of fungi which become implanted under the skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
, often by thorns or splinters. Chromoblastomycosis spreads very slowly; it is rarely fatal and usually has a good prognosis
Prognosis
Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...
, but it can be very difficult to cure. There are several treatment options, including medication and surgery.
Features
The initial trauma causing the infection is often not noticed or forgotten. The infection builds at the site over a period of years, and a small red papulePapule
A papule is a circumscribed, solid elevation of skin with no visible fluid, varying in size from a pinhead to 1 cm.With regard to the quote "...varying in size from a pinhead to 1cm," depending on which text is referenced, some authors state the cutoff between a papule and a plaque as 0.5cm,...
(skin elevation) appears. The lesion is usually not painful and there are few, if any symptoms. Patients rarely seek medical care at this point.
Several complications may occur. Usually, the infection slowly spreads to the surrounding tissue while still remaining localized to the area around the original wound. However, sometimes the fungi may spread through the blood vessels or lymph vessels
Lymphatic system
The lymphoid system is the part of the immune system comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph unidirectionally toward the heart. Lymphoid tissue is found in many organs, particularly the lymph nodes, and in the lymphoid follicles associated...
, producing metastatic lesions at distant sites. Another possibility is secondary infection with bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
. This may lead to lymph stasis (obstruction of the lymph vessels) and elephantiasis
Elephantiasis
Elephantiasis is a disease that is characterized by the thickening of the skin and underlying tissues, especially in the legs and male genitals. In some cases the disease can cause certain body parts, such as the scrotum, to swell to the size of a softball or basketball. It is caused by...
. The nodules may become ulcerated, or multiple nodules may grow and coalesce, affecting a large area of a limb.
Diagnosis
The most informative test is to scrape the lesion and add potassium hydroxidePotassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
(KOH), then examine under a microscope. (KOH scrapings are commonly used to examine fungal infections.) The pathognomonic
Pathognomonic
Pathognomonic is a term, often used in medicine, that means characteristic for a particular disease. A pathognomonic sign is a particular sign whose presence means that a particular disease is present beyond any doubt...
finding is observing Medlar bodies, sclerotic cells. Scrapings from the lesion can also be cultured
Microbiological culture
A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory conditions. Microbial cultures are used to determine the type of organism, its abundance in the sample being tested,...
to identify the organism involved. Blood tests and imaging studies are not commonly used.
On histology, chromoblastomycosis manifests as pigmented yeasts resembling "copper pennies." Special stains, such as periodic acid schiff and Gömöri methenamine silver, can be used to demonstrate the fungal organisms if needed.
Pathophysiology
Chromoblastomycosis is believed to originate in minor trauma to the skin, usually from vegetative material such as thorns or splinters; this trauma implants fungi in the subcutaneous tissue. In many cases the patient will not notice or remember the initial trauma, as symptoms often do not appear for years. The fungi most commonly observed to cause chromoblastomycosis are:- Fonsecaea pedrosoiFonsecaea pedrosoiFonsecaea pedrosoi is a species of fungus in the genus Fonsecaea. First described in 1922 as Hormodendrum pedrosoi by Émile Josef Alexander Brumpt, it is known from South America.It can be associated with chromoblastomycosis....
- Phialophora verrucosaPhialophora verrucosaPhialophora verrucosa is a species of fungus in the genus Phialophora.It can be associated with chromoblastomycosis....
- Cladosporium carrionii
- Fonsecaea compactaFonsecaea compactaFonsecaea compacta is a species of Fonsecaea.It can be associated with chromoblastomycosis....
Over months to years, an erythematous papule appears at the site of inoculation. Although the mycosis slowly spreads, it usually remains localized to the skin and subcutaneous tissue. Hematogenous and/or lymphatic spread may occur. Multiple nodules may appear on the same limb, sometimes coalescing into a large plaque. Secondary bacterial infection may occur, sometimes inducing lymphatic obstruction. The central portion of the lesion may heal, producing a scar, or it may ulcerate.
Treatment
Chromoblastomycosis is very difficult to cure. There are two primary treatments of choice.- ItraconazoleItraconazoleItraconazole , invented in 1984, is a triazole antifungal agent that is prescribed to patients with fungal infections. The drug may be given orally or intravenously.-Medical uses:...
, an antifungal azoleAzoleAn azole is a class of five-membered nitrogen heterocyclic ring compounds containing at least one other non-carbon atom of either nitrogen, sulfur, or oxygen. The parent compounds are aromatic and have two double bonds; there are successively reduced analogs with fewer...
, is given orally, with or without flucytosineFlucytosineFlucytosine, or 5-fluorocytosine, a fluorinated pyrimidine analogue, is a synthetic antimycotic drug.It is structurally related to the cytostatic fluorouracil and to floxuridine. It is available in oral and in some countries also in injectable form. A common brand name is Ancobon. Flucytosine was...
(5-FC). - Alternatively, cryosurgeryCryosurgeryCryosurgery is the application of extreme cold to destroy abnormal or diseased tissue. The term comes from the Greek words cryo and surgery meaning "hand work" or "handiwork"....
with liquid nitrogenLiquid nitrogenLiquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4...
has also been shown to be effective.
Other treatment options are the antifungal drug terbinafine
Terbinafine
Terbinafine hydrochloride is a...
, an experimental drug posaconazole
Posaconazole
Posaconazole is a triazole antifungal drug.Posaconazole is marketed in the United States, the European Union, and in other countries by Schering-Plough under the trade name Noxafil...
, and heat therapy
Heat therapy
Heat therapy, also called thermotherapy, is the application of heat to the body for pain relief and health. It can take the form of a hot cloth, hot water, ultrasound, heating pad, hydrocollator packs, whirlpool baths, cordless FIR heat therapy wrap, and many others. It can be beneficial to those...
.
Antibiotics may be used to treat bacterial superinfections.
Amphotericin B
Amphotericin B
Amphotericin B is a polyene antifungal drug, often used intravenously for systemic fungal infections...
has also been used.
Prognosis
The prognosis for chromoblastomycosis is very good for small lesions. Severe cases are difficult to cure, although the prognosis is still quite good. The primary complications are ulceration, lymphedemaLymphedema
Lymphedema , also known as lymphatic obstruction, is a condition of localized fluid retention and tissue swelling caused by a compromised lymphatic system....
, and secondary bacterial infection. There have been a few cases reported of malignant
Malignant
Malignancy is the tendency of a medical condition, especially tumors, to become progressively worse and to potentially result in death. Malignancy in cancers is characterized by anaplasia, invasiveness, and metastasis...
transformation to squamous cell carcinoma
Squamous cell carcinoma
Squamous cell carcinoma , occasionally rendered as "squamous-cell carcinoma", is a histologically distinct form of cancer. It arises from the uncontrolled multiplication of malignant cells deriving from epithelium, or showing particular cytological or tissue architectural characteristics of...
. Chromoblastomycosis is very rarely fatal.
Prevention
There is no known preventative measure aside from avoiding the traumatic inoculation of fungi. At least one study found a correlation between walking barefoot in endemicEndemic (epidemiology)
In epidemiology, an infection is said to be endemic in a population when that infection is maintained in the population without the need for external inputs. For example, chickenpox is endemic in the UK, but malaria is not...
areas and occurrence of chromoblastomycosis on the foot.
Epidemiology
Chromoblastomycosis occurs around the world, but is most common in rural areas between approximately 30° N and 30° S latitudeLatitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
. Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
have the highest incidence. Over two thirds of patients are male
Male
Male refers to the biological sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...
, and usually between the ages of thirty and fifty. A correlation with HLA
Human leukocyte antigen
The human leukocyte antigen system is the name of the major histocompatibility complex in humans. The super locus contains a large number of genes related to immune system function in humans. This group of genes resides on chromosome 6, and encodes cell-surface antigen-presenting proteins and...
-A29 suggests that genetic factors may play a role as well.