Simple notes in fungal infection of the skin

Pityriasis Versicolor
It is caused by yeasts (Pityrosporum orbiculare and P. ovale) providing widespread fine scaly macules on the upper trunk and back. The colour of the lesions varies. The lesions are pale in dark skin and darker in fair skin. Recurrent attacks are common. The diagnosis is established clinically and can be supported by the faint yellow fluorescence under Wood's light in the affected areas.
Treatment
1) Topical treatment
a) Imidazoles cream e.g. clotrimazole, miconazole, isoconazole
b) Ketoconazole shampoo
c) 2.5% selenium sulphide shampoo
d) 3% salicylic acid in spirit
e) 20% sodium thiosulphate in spirit
2) Systemic treatment
a) Oral ketoconazole 200 mg daily for 5 days
b) Oral itraconazole 100 mg daily for 5 days
Tinea Pedis
It is a fungal infection of the toe webspaces and the soles. Trichophyton rubrum (T. rubrum), T. Mentagrophytes Var. interdigitale and Epidermophyton floccosum are the commonest causative organisms. There are 3 main clinical patterns.
1) Chronic Plantar Scaling
It presents as a "Moccasin" distribution, on plantar surface and the edges of feet. Peeling of skin and scales are common. Hyperkeratosis may develop on weight-bearing areas.
2) Acute Vesicular Tinea Pedis
Sudden eruption of pruritic or painful vesicles develop on the soles. The eruption is usually unilateral. This pattern may give rise to Id reaction presenting as symmetrical, vesicular pompholyx at sites distant from the site of active fungal infection.
3) Interdigital Tinea Pedis
Peeling, maceration and fissuring occurs frequently in the lateral toe clefts. It is usually very itchy and is more common in people with sweaty feet or occlusive foot-wear.
Tinea Manuum
T. rubrum is the commonest cause. There is unilateral scaling particularly in the skin creases and the nails are usually involved.


Tinea Unguium
Infection of nail and/or the nail bed with dermatophyte fungi is usually due to T. rubrum. It presents as distal nail edge onycholysis with subungual tan crumbly debris, subungual hyperkeratosis and brownish discolouration from secondary colonization by non-pathogenic fungi e.g. Aspergillus.


. Tinea Cruris
Tinea cruris presents as itchy advancing red, sharply demarcated skin rashes enlarging from inguinal folds down inner thigh or into pubic area. Central healing followed by post-inflammatory hypopigmentation is its characteristic. It is usually caused by Trichophyton rubrum, Epidermophyton floccosum and T. mentagrophytes var. interdigitale.


Tinea Capitis
Scalp ringworm is uncommon in H.K. nowadays. It appears as scattered scaly patches containing broken hairs. The lesions may be asymptomatic or mildly itchy. In general, the pattern of involvement can be classified as ectothrix, endothrix, kerion and favus respectively. In severe situation, boggy mass of inflamed and purulent skin known as kerion may occur especially by animal infections. Usually human infections produce minor degrees of erythema and scaling while animal infections cause considerable inflammation.

. Tinea Corporis
It refers to the dermatophyte infection of smooth skin. The lesion is identical to that of tinea cruris but occurs on the trunk and limbs. It is easily misdiagnosed as discoid eczema or pityriasis rosea.

Tinea Faciei
It presents as an amorphous, asymptomatic reddish patch, which may be photosensitive. The skin lesion may be mistaken for polymorphic light eruption, lupus erythematosus and contact dermatitis. It is commonly caused by Trichophyton rubrum, T. mentagrophytes and Microsporum species. Outbreak of zoophilic species induced tinea faciei has been found in Hong Kong.
Diagnosis
1) Wood's light (more useful in Tinea capitis)
2) Microscopic examination of scrapings and clippings in 10% - 30% KOH
3) Culture
Treatment of Tinea infection
1) Topical treatment
Imidazole e.g. miconazole (Daktarin), clotrimazole (Canesten, Lotremin), Tionazole (Trosyd), Ketoconazole (Nizoral), Isoconazole (Travogen), Bifonazole (Mycospor)
Allylamine e.g. Terbinafine (Lamisil), Natifine (Exoderil)
Others e.g. Tolciclate (Tolmicen), whitfield's ointment, mycota, Castellani's paint, Ciclo-piroxolamine (Batrafen), Tolnaftate (Tinaderm), Zinc Undecenoate (Tineafax)
2) Systemic treatment
Griseofulvin, ketoconazole, Itraconazole, Terbinafine
Candidiasis
Candida infections caused by yeast-like fungi Candida albicans commonly occur in moist, flexural sites. It is more common at the extremes of age and during pregnancy. Predisposing factors include diabetes mellitus, pregnancy, broad-spectrum antibiotics, obesity, Cushing disease, uraemia, malignant disease and immunodeficiency. It can present as 10 clinical patterns, depending on the site of involvement. They are the oral thrush, angular cheilitis, genital candidiasis (vulvovaginitis), candida balanitis, candida intertrigo, chronic paronychia, chronic onychia, pruritus ani, erosio interdigitalis and candida granuloma. The diagnosis is arrived clinically and confirmed by fungal culture.
Treatment
1) Topical treatment
Nystatin, imidazole cream, amphotericin lozenges (in oral candidiasis)
2) Systemic treatment
Oral fluconazole, itraconazole, ketoconazol