Fungal infections of the skin

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Fungal infections of the skin are widely distributed and can occur at any part of the body. Fungal infections of the skin involve persons of all age groups and of both sexes. Depending on which part of the skin is involved are classified into Superficial. Subcutaneous and deep infections. Fungal infections are more common in persons with poor personal hygiene and HIV positive patients.

Superficial mycoses

These are primarily caused by dermatophytes (Trichophyton, epidermophyton and microsporum) which are primarily found in the skin and transmitted from person to person. Besides humans, source of infection may be from animals and soil.

Fungal infections of the skin are diagnosed by their clinical picture (Brown circular, polycyclic and annular lesions). There is some scaling and the lesion tends to spread peripherally with central clearing. Potassium hydroxide preparations reveal the true nature of the infection. Examination with woods light is an invaluable help.

Tinea capitis (Dermatophytosis of scalp)

Ringworm of the scalp is primarily caused by microsporon (Human I animal form) or trichophyton. It generally involves young children (Boys more than girls) since adults are protected by fungstic properties of sebum. The infection spreads by close contact as well as by use of hair clippers and caps. Animal form spreads by fondling of dogs or kittens.

Clinically there are circular patches of short, bent or broken hair. The scalp shows grayish scales without redness. Yellowish crusts with follicular pustules may be formed. Rarely when infection results in inflammatory lesion (Boggy, dusky, dome shaped swelling which discharges a serous exudate) it is called Kerion which is more common with Trichophyton infection.

Another form of Tinea capities is black dot variety where hair which has broken at the level of the scalp in areas of partial alopecia, give appearance of black dots. Differentiation of tinea is often required from infective dermatitis when it involves large areas of scalp. Presence of broken hairs in tinea helps in differentiating the condition.

Diagnosis is made by examining with Woods light. Affected hair can be removed for microscopy and culture. Treatment shall depend on the type of organism grown on culture. Local application consists of application of whitfield ointment over the scalp. Hair should be trimmed short. Local application of the ointment shall serve the purpose of fungistatic action on the skin, Antifungals (Clotrimazole, miconazole, ketoconazole) applied locally are also beneficial. 1% clotrimazole lotion is usually used but as penetration is poor, so systemic antifungal is used simultaneously.

Besides this systemic use of antifungal is also indicated in addition to topical therapy in wide spread involvement of scalp. Commonly used drugs include Griseofulvin in the dose of 10 mg/kg day in two divided doses for 4-6 weeks and fluconazole in the initial dose of 150 mg followed by weekly dose for 6 weeks.

Tinea corporis

It mainly involves the flexural areas like anal region, perineum, scrotum, buttocks, genitocrural folds and in obese women areas round about the waist. The causative organism is T. Rubrum. Lesions are annular, polycyclic with edges showing some scaliness, erythema and vesiculation. Larger lesions may be formed due to coalescence of lesions. Tinea corporis has to be differentiated from infective dermatitis and contact dermatitis. Microscopy makes the diagnosis cleat

Tinea cruris

The clinical picture here is like that of Tinea corporis. As groin is mainly involved, there is severe degree of itching and erythema. The lesion generally starts from the apex of the groin and then extends to inner part of the thighs and genitalia. Organism most often is epidermophyton floccosum but T Rubrum may also be responsible. Secondary infection may supervene. It is more common in males than females and in obese and diabetics.

Tinea pedis (Ring worm of the foot)

It is a common form of infection in people living in hot, humid weather. Incidence is higher in summer and rainy season than in winter. Predisposing factors include excessive sweating, occlusive foot wear, and walking bare foot on contaminated floors. Infection is spread through use of bath mats, tubs and swimming pools. Individual susceptibilities may be because of excessive sweating crowded toes, foot deformities, faulty foot wear and use of thick socks.

It is a disease of late childhood or young adults. Males are affected more as compared to females. T.Rubrum is the most common infective organism. Other organisms responsible are T. Mentagrophytes or F. Floccosum. Arthrospores can survive in human skin for long periods ranging from months to years. Various forms of tinea pedis are described:

1. Inter digital type (Acute and chronic). It is the most common type.

2. Moccasin type (Chronic hyperkeratotic or dry type). Common in atopic individuals.

3. Inflammatory or bullous (vesicular) type. It is the least common type.

4. Ulcerative type. It is extension of interdigital type and is as a result of maceration and secondary bacterial infection.

Clinically it usually presents with fissuring I scaling on the inner side of foot spreading to the interdigital areas, flexures and clefts of the toes. Soon it spreads to the soles and involves the dorsal aspect of foot. The lesions are generally asymmetrical. Groups of vesicles of various size may appear and when secondary bacterial infection appears these may become seropurulent.

In inter digital type, there is maceration, peeling and fissuring of the toe webs.

Moccasin type is characterized with well- demarcated erythema with fine white scaling and hyperkeratosis. This type is confined to soles, heels and lateral borders of feet. When secondary bacterial infection supervenes, bullae or vesicles may appear and this is called bullous type. Here infection may spread to the nails of hands and feet. Inflammatory or bulbous type is the least common form of the disease. It is usually caused by T. Mentagrophytes.

Diagnosis: Microscopic examination is required to confirm the presence of organism. This is done by examining the scrapings from the suspected vesicles. It will show the hyphae.

Fungal culture: Dermatophytes can be isolated from inter spaces and toe webs. Bacterial culture is required for isolating secondary organisms.

Management: Maintain proper hygiene of feet. Avoid close fitting shoes. Use of cotton socks and daily change is advised.

Topical antifungal agents are advised to be applied locally twice a day. In addition systemic drugs be given. Griseofulin for 8-12 weeks. Fluconazole (150 mg weekly) for 4 weeks. Itraconazole (200 mg twice a day for 7 days). In severe forms of disease especially inflammatory/bullous type, corticosteroids are indicated.

Tinea unguium (Ringworm of the nails)

It is fungus infection of the nails and is mainly due to T.Rubrum, or T. Mentagrophytes or epidermophyton. Young and middle aged adults are usually affected. It is asymmetrical involvement of the nails starting from the base of the free edge of the nail margins or lateral border. Nails become discolored, thickened, rough, friable, and may be easily shed. Many nails may be affected at the same time. There may be subungual collection of keratotic material and debris while matrix of the nail plate remains uninvolved.

Ringworm of the nails has to be differentiated mainly from psoriasis and eczema. While in psoriasis many nails in symmetrical manner are involved; in Ringworm involvement only one or two nails are involved with dirty grey yellowish discoloration. Diagnosis is made by microscopic examination of the scrapings from nails and demonstration of mycelial filaments. Treatment of T. unguium is difficult and prolonged.

Removal of nail plate and application of antifungal cream (Clotrimazole 1% / Miconazole 2% / Ketoconazole 2%) is helpful. Griseofulvin given orally (10 mg/kg! day) for period ranging from 8-12 months in case of fingernails and 1—114 years in toe nails is helpful. Treatment should continue till the involved nails have been replaced. Fluconazole offers shorter treatment and is administered in dose of 150 mg/week for 3 months for fingernails and for 6 months for toe nails.

Terbenafine in the dose of 250 mg daily for 3 months for finger nails and 6 months for toe nails is another alternative drug.



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