Tinea versicolor
Introduction
Introduction to tinea versicolor It is commonly known as sweat stains, a mild fungal infection of the skin's superficial stratum corneum, often asymptomatic, or only mild itching. The disease is caused by the lipophilic yeast round or P. ovale. Chronic infection, malnutrition, etc., can induce this disease. Symptoms manifest as many small spots at first, and soon the detachment area on the spot expands and merges into a ring shape. The color is generally yellow-brown or dark brown, and round or oval rash of miliary, soy or even nail size can appear. Covered with extremely thin braided scales. basic knowledge The proportion of illness: 0.003% Susceptible people: no specific population Mode of infection: non-infectious Complications: abscess seborrheic dermatitis psoriasis
Cause
The cause of tinea versicolor
(1) Causes of the disease
Pityrosporum has been proven to be the pathogen of the disease, a conditional pathogen, when the skin is sweaty, poor sanitation, long-term application of corticosteroids and chronic consumptive diseases, the bacteria can be caused by saprophytic yeast The type is transferred into a pathogenic mycelium type, which causes skin disease. The pathogen is Malassezia furfur, also known as T. variabilis. Trichophyton rubrum is a normal flora of human skin. It has been reported to have been isolated from the scalp of 92% of normal people. Other parts of the belt include the back, the trunk, the limbs, and the face. Child prevalence is related to age. The older the age, the higher the rate of infection. P. variabilis usually rots on the surface layer of the stratum corneum and is in the form of spores. Under certain conditions, it will change from spore phase to hyphae phase, which is infectious and invades surrounding tissues to cause damage. Inducing factors include systemic or topical use of corticosteroids, skin oils and fats, chronic infections, malnutrition, extracellular glycogen deposition, and family inheritance. But the most common clinical factors are high temperatures and excessive sweating.
The distribution of tinea versicolor is global. It is common in summer and autumn in temperate regions. It is very popular in tropical and subtropical regions. The incidence rate of residents in many countries such as Mexico, India and Cuba is as high as 50%. The incidence rate in China is higher than that in the north. Most of the patients were adults, more men than women. Infected by direct or indirect contact. Do not infect animals.
P. stipitis is lipophilic, so skin lesions are mostly distributed in areas rich in sebaceous glands. P. stipitis can produce dihydroxy acids which have inhibitory effects on melanocytes and cytotoxicity, thereby causing hypopigmentation of tinea versicolor damage. It is also believed that it is caused by the fact that T. variabilis and its metabolites can prevent sunlight from penetrating into the local skin and interfere with the formation of melanin in the local skin.
Two forms of P. stipitis can be isolated from human skin, called Pityrosporum orbiculae and Pityrosporum ovale. They are generally considered to be synonymous.
(two) pathogenesis
P. stipitis is lipophilic, so skin lesions are mostly distributed in areas rich in sebaceous glands. P. stipitis can produce dihydroxy acids which have inhibitory effects on melanocytes and cytotoxicity, thereby causing hypopigmentation of tinea versicolor damage. It is also believed that it is caused by the fact that T. variabilis and its metabolites can prevent sunlight from penetrating into the local skin and interfere with the formation of melanin in the local skin.
Prevention
Speckle prevention
Primary prevention
(1) Develop good personal hygiene habits, and take a bath and change underwear frequently.
(2) Reasonable nutrition, the disease can be induced by malnutrition, and patients who are treated with corticosteroids should pay attention to observe and prevent the disease.
2. Secondary prevention
(1) If the patient with tinea versicolor is not cured, it can be cured for many years, but as long as it is taken seriously, it is easier to cure the medicine because the spotted fungus grows on the shallowest layer of the skin, and the topical antifungal drugs can work. Generally, it can be used in 25% to 40% sodium thiosulfate solution. After 5 minutes, 3% dilute hydrochloric acid solution is used. It is best to wash the scales with hot water soap before using the medicine. You can also use 10% glacial acetic acid solution, 1%. Clotrimazole, econazole cream or tincture, administered twice daily.
(2) In order to prevent the recurrence of the disease, it is advisable to use the drug for 2 weeks after the disease has healed, and at the same time wear anti-mold pants, which can not only help the treatment but also prevent it.
(3) Borelli D et al reported that oral ketoconazole (a broad-spectrum antifungal agent) can not only treat tinea versicolor, but also prevent its recurrence.
(4) The shirts, trousers, sheets, pillowcases, etc. used by the patients during the treatment should be disinfected. The disinfection method can be sterilized by boiling (15~30min), or after scalding with boiling water, and fumigation with formalin. disinfection.
Complication
Comminuted plaque Complications abscess seborrheic dermatitis psoriasis
Severe cases are called acne-like pityrosporum folliculitis, and abscess formation. P. variabilis can also affect obstructive dacryocystitis caused by lacrimal sac, and also has a relationship with seborrheic dermatitis, dandruff and psoriasis.
Symptom
Symptoms of tinea versicolor Common symptoms Itching papules inguinal itch rashes small blisters on the back
From the beginning, there are many small spots, and soon the desquamation area is enlarged, and it is fused into a ring shape and visible decolorizing spots. The color of the damage varies with the skin color of the patient and is related to the sun, the severity of the condition, and the like. Sometimes it can be yellowish brown or dark brown patches, and it is light gray on dark skin, which is extremely difficult to identify. Sometimes it is located around the pores, it has papular lesions, and there is very little inflammatory reaction, which occurs in the chest, back and abdomen. A clinical variant can sometimes be seen in black infants in the tropics. Damage occurs in the diaper area and develops rapidly to cause localized discoloration. This type is white tinea versicolor or parasitic depigmentation. Generally, the skin lesions are mainly stained spots and/or depigmented spots, which may have a itchiness and are more obvious after sweating.
Examine
Spotted plaque
1, blood routine: blood routine is the most general, the most basic blood test. Blood consists of two major parts, fluid and tangible cells, which are routinely tested for blood.
2, liver function test: It is through various biochemical test methods to detect various indicators related to liver function metabolism to reflect the basic state of liver function. Because of the diverse functions of the liver, there are many methods for liver function tests. Which specific examination should be performed, one or several of the examinations should be selected in combination with medical history and symptoms, which is helpful for the diagnosis and evaluation of liver function.
3, specimen smear staining, direct microscopic examination of scaly visible short rod-shaped hyphae and round spores.
4, special examination of skin diseases.
Diagnosis
Diagnosis and identification of tinea versicolor
diagnosis
1, the incidence of summer, hidden in winter.
2, it is good to the chest, back, armpit, neck and other sweat gland rich parts, can also invade the head.
3, the skin lesions are punctate or small pieces of light brown, grayish white fine scaly.
4, lack of symptoms, sometimes slightly itching.
According to the clinical manifestations, the direct microscopic examination of the lesions can be confirmed by the typical hyphae.
1. Direct microscopy: direct microscopic examination of scrape and 10% KOH solution, see short and thick, two rounded, slightly curved hyphae, generally 10 ~ 40m long, 2.5 ~ 4.0m wide, there are piles Round or oval thick-walled spores, 3 to 8 m in diameter, sometimes with spores, can be confirmed by direct microscopic examination.
2. Culture: Add 1~2ml of olive oil or other vegetable oil on the surface of Sabouraud agar or other conventional medium, inoculate the scales and incubate at 37 °C. After 3 days, there will be creamy yeast-like colonies, and the microscopic examination will be mainly yeast-like cells. Budding, culture is generally not a routine for diagnosis.
3. Wu's lamp inspection: the Wu's lamp checks the tinea skin lesions and the scraped scaly has golden yellow fluorescence.
Histopathology: mild to moderate epidermal hyperplasia, a small amount of mononuclear cells infiltrated in the dermis, short and thick in the middle or bottom of the stratum corneum, slightly curved, sausage-like hyphae and piles of round or oval thick-walled spores Some can be budding and are more clearly stained with PAS and GMS.
Differential diagnosis
It should be differentiated from the following diseases.
(1) Vitiligo: It is mainly white in the form of skin pigmentation, and its pigmentation on the edge. Generally, there is no scaling, no itching, no history of excessive sweating, etc., and it is more helpful to identify the persistent negatives.
(2) Rose pityriasis: The disease has a mother spot at the beginning, which immediately spreads to the whole body. It is a red elliptical spot with a scaly scale in the center. Its long axis is consistent with the direction of the dermatoglyph and the fungus is negative.
(3) Red sputum: often limited to the skin wrinkles or folds of the underarms, under the breasts and groin, the skin lesions are slightly red, the scales are not easy to fall off, 10% potassium hydroxide smear is not easy to find red sputum, need Special staining can be found.
