1. Superficial mycoses
Tinea versicolor or pityriasis versicolor
Tinea versicolor or pityriasis versicolor is a common skin infection caused by Malassezia furfur. This yeast is normally found on the human skin and only becomes troublesome under certain circumstances, such as a warm and humid environment. In tropical climate, the condition is more common than in temperate zones and as many as 40% of some apparently healthy populations may be affected.
Microscopic: tinea versicolor, "spaghetti and meatballs" appearance
Taken from http://missinglink.ucsf.edu/lm/DermatologyGlossary/img/Dermatology%20Glossary/Glossary%20Clinical%20Images/KOHtineaversicolor.jpg
The development of disease is thought to follow a shift in the balance between the host and resident yeast flora. There are many factors contributing to this change. Infection is more prone to be caused by environmental risk factors and individual host susceptibility such as genetic susceptibility. Most of the transmission is through direct contact with the yeast.
Signs and Symptoms:
· Generally oval or irregularly-shaped spots of 1/4 to 1 inch in diameter, often merging together to form a larger patch
· Occasional fine scaling of the skin producing a very superficial ash-like scale
· Pale, dark tan, or pink in color, with a reddish undertone that can darken when the patient is overheated, such as in a hot shower or during/after exercise
· Sharp border
· commonly affect the back, underarm, upper arm, chest, lower legs, and neck. Occasionally it can also be present on the face.
· In people with dark skin tones, pigmentary changes such as hypopigmentation (loss of color) are common, while in those with lighter skin color, hyperpigmentation (increase in skin color) are more common. These discolorations have led to the term "sun fungus".
· Topical antifungal medications such as selenium sulfide, ketoconazole, clotrimazole, miconazole or terbinafine is applied to dry skin and washed off after 10 minutes, repeated daily for 2 weeks.
· Oral antifungal prescription only medications include ketoconazole or fluconazole in a single dose, or ketoconazole daily for 7 days, or itraconazole daily for 3-7 days. The single-dose regimens can be made more effective by having the patient exercise 1-2 hours after the dose, to induce sweating. The sweat is allowed to evaporate, and showering is delayed for a day, leaving a film of the medication on the skin.
Prevention:Infection may be reduced by intermittent application of topical agents (such as tea tree oil) or adding a small amount of anti-dandruff shampoo to water used for bathing.
2. Cutaneous mycoses
Dermatophytosis is caused by fungi in the genera Microsporum, Trichophyton and Epidermophyton. Belonging to pathogenic members of the keratinophilic (keratin digesting) soil fungi. Microsporum and Trichophyton are human and animal pathogens. Epidermophyton is a human pathogen.Dermatophytes grow best in warm and humid environments and are, therefore, more common in tropical and subtropical regions. The geographic distribution varies with the organism. M. canis, M. nanum, T. mentagrophytes, T. verrucosum and T. equinum occur worldwide. T. simii (found in monkeys) occurs only in Asia.
Infection occurs by contact with arthrospores (asexual spores formed in the hyphae of the parasitic stage) or conidia (sexual or asexual spores formed in the “free living” environmental stage). Infection usually begins in a growing hair or the stratum corneum of the skin. Dermatophytes do not generally invade resting hairs, since the essential nutrients they need for growth are absent or limited. Hyphae spread in the hairs and keratinized skin, eventually developing infectious arthrospores. Transmission between hosts usually occurs by direct contact with a symptomatic or asymptomatic host, or direct or airborne contact with its hairs or skin scales. Geophilic dermatophytes, such as M. nanum and M. gypseum, are usually acquired directly from the soil rather than from another host.
Signs and Symptoms:
Tinea capitis, tinea barbae and tinea faciei are generally treated with systemic antifungals. Topical lotions or shampoos are sometimes used to decrease shedding of fungi and spores. Tinea corporis can usually be treated with nonprescription antifungals. Prescription drugs may be required if the fungus infects the hairs and recrudescence occurs. Tinea manuum is usually treated with topical drugs and emollients.
Control of the disease in animals can prevent some cases of dermatophytosis in humans. Infected animals should be treated and the premises and fomites should be disinfected. Gloves and protective clothing should be used during contact with infected animals. Such contact should be avoided as much as possible. Similar measures can prevent infections with anthropophilic dermatophytes.
3. Subcutaneous mycoses
The fungi that cause subcutaneous mycoses normally reside in soil or vegetation. They enter the skin or subcutaneous tissue by traumatic inoculation with contaminated material. In general, the lesions become granulomatous and expand slowly from the area of implantation. Extension via the lymphatic draining the lesion is usually slow. These mycoses are usually confined to the subcutaneous tissues, but in rare cases they become systemic and produce life-threatening disease. Chromoblastomycosis is mainly caused by phialophora verrucosa, fonsecaea pedrosoi, Rhinocladiella aquaspersa, Fonsecaea compacta, and Cladophilophora carrionii.
Cladosporium (Cladophialophora) carrionii, magnified 475X. The C. carrionii fungus is a common cause of chromoblastomycosis infections, and is particularly prevalent in arid and semi-arid areas, most often in tropical and subtropical zones
Taken from http://pathmicro.med.sc.edu/mycology/cladophialophora.jpg
The organisms responsible for Chromoblastomycosis are found in the soil, endemic in the tropicas. They are introduced into tissues by trauma from eg :thorns or splinters. Transmission from person to person does not occur.
Signs and symptoms:
· a small red papule (skin elevation)
· Painless lesion
· Satellite lesion form if patient scratches
· Formation of cauliflower-like warty swellings which spread over the years
· Foul discharge may occur in secondary infection
· Nodular pattern becomes tumorous, large, rough and ulcerating
· Several complications may occur
Sugical excision with wide margins is the therapy of choice for small lesions. Chemotherapy with flucytosine or itraconazole may be efficacious for larger lesions. Local applied heat is also beneficial. Relapse is common.
There is no known preventative measure aside from avoiding the traumatic inoculation of fungi.
4. Endemic mycoses
Histoplasmosis, also known as Darling's disease, is caused by the dimorphic fungus Histoplasma capsulatum. This sexually reproducing fungal species is naturally found in the soil (often associated with avian and bat guano) and is endemic in tropical areas of the world. The fungus exists in a hyphal form in the soil and exists as small conidia in the human host. In C.albicans both the yeast and hyphal forms are important in virulence while in H.capsulatum (and other systemic mycoses) only the conididal form is associated with disease. Inhalation of the infectious propagules by normal healthy individuals usually results in a self limiting sub-clinical infection.
Asexual spores (conidia). Tuberculate macroconidia of Histoplasma capsulatum.
Histoplasmosis can be transmissed through breathing in airborne spores. The initial infection often occurs without causing symptoms, and most persons usually will not develop subsequent disease, unless the exposure was heavy.
Long-term smokers and those with preexisting lung disease may be at higher risk for developing the disease.
People with severely damaged immune systems are vulnerable to a very serious disease known as progressive, disseminated histoplasmosis. Nationwide, about 5 percent of people with AIDS will develop histoplasmosis. In geographic areas where the fungus is common, people with AIDS are at higher risk for disseminated histoplasmosis.
Signs and symptoms:
· symptoms start within 3 to 17 days after exposure; the average is 12-14 days. Most affected individuals have clinically-silent manifestations and show no apparent ill effects.
· The acute phase of histoplasmosis is characterized by non-specific respiratory symptoms, often cough or flu-like. Chest X-ray findings are normal in 40-70% of cases.
· Chronic histoplasmosis cases can resemble tuberculosis; disseminated histoplasmosis affects multiple organ systems and is fatal unless treated.
· Severe infections can cause hepatosplenomegaly, lymphadenopathy, and adrenal enlargement.
· Lesions have a tendency to calcify as they heal.
· Ocular histoplasmosis damages the retina of the eyes. Scar tissue is left on the retina which can experience leakage, resulting in a loss of vision.
Antifungal medications are used to treat severe cases of acute histoplasmosis and all cases of chronic and disseminated disease. Typical treatment of severe disease first involves treatment with amphotericin B, followed by oral itraconazole. In many milder cases, simply itraconazole is sufficient. Asymptomatic disease is typically not treated. Past infection results in partial protection against ill effects if reinfected.
Avoid areas where disease is prominent.
Done be: Liu Qian and Dorene