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Superficial fungal skin infections

Siobhan Hicks
RGN BSc
Nurse Practitioner in Primary Care
Lecturer in Public Health and Primary Care
London

Superficial fungal infections are very common and usually mild, and affect the outer layers of the skin, hair and nails. However, in people with a suppressed immune system they can cause serious disease.
Dermatophyte fungi are the ringworm fungi or tinea, which are dependant on a host for survival. The host may be an animal ("zoophilic"), a human ("anthropophilic") or live in the soil ("geophilic"). Dermatophytes are also recognised by their spores: for example, Trichophyton ("T"), Microsporum ("M") and Epidermophyton ("E"). Common organisms within these groups are listed in Box 1.

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The main causative organisms in fungal infections are dermatophytes, yeasts and moulds. These will now be explored.

Tinea barbae
This is an infection of the beard and moustache area, usually affecting adult men. The hair becomes infected with an ectothrix pattern, ie, the fungal filaments and spores are on the outside of the hair shaft. It is caused by zoophilic fungi T verrucosum and T equinum and is usually due to direct contact with an infected animal, but is occasionally passed from one person to another. The patient presents with inflamed lumpy pustules and crusting around the hairs, which can be pulled out easily. Tinea barbae is not itchy or painful.

Tinea capitis
Tinea capitis is a scalp infection that is common in children, caused by a zoophilic fungus M canis, often following contact with an infected kitten or older dog. Anthropophilic T tonsurans can also be responsible.
Classification depends on how the fungus invades the hair shaft - it is either ectothrix, as described previously, or an endothrix infection in which the hair shaft is invaded with fungal branches or spores.
This fungus can contaminate hairbrushes, clothing, towels and seat backs and the spores live for a long time.
The patient presents with a dry scaly scalp, smooth areas of hair loss, inflamed masses and swollen lymph nodes. If this is not treated it can lead to scarring and bald patches.

Tinea corporis
Tinea corporis or ringworm is the name used for fungal infection of the trunk, legs or arms. It is often spread from the feet or the nails and infection derives from M canis and T verrucosum.
The term ringworm refers to round or oval red scaly patches that are itchy and less scaly in the middle. Children do not need to miss school once treatment has started.

Tinea cruris
This is an infection of the groin, most often seen in adult men. It is often spread from the feet or nails and is contracted by scratching or use of an infected towel.
The rash is similar to ringworm with a scaly raised red border that spreads down the inner thighs from the groin or scrotum and may form ring like patterns on the buttocks. It does not usually affect the genitalia and is very itchy.

Tinea faciei
This infection occurs on the face, and is most common in children. It can be due to an anthropophilic fungus but commonly comes from the feet or nails. Zoophilic fungi such as M canis and T verrucosum are common. The onset of this rash can be acute or chronic and it is mainly asymptomatic; however, it is often aggravated by sunlight.
The appearance is of round or oval scaly patches that are less scaly or healed in the middle. It is not usually symmetrical and is frequently misdiagnosed because of prior treatment with topical steroids.

Tinea manuum
Tinea manuum usually affects the dominant hand and is commonly associated with tinea pedis (athlete's foot). It is frequently misdiagnosed because it is often mistaken for psoriasis or dermatitis. Infection is through contact with another person or direct contact with an infected animal or soil, indeed it is more likely in those with manual jobs especially if they sweat profusely or have hand dermatitis.
The appearance of the rash is asymmetrical if both hands are affected. In chronic infections the skin becomes white with a scaly surface, and it is not unusual for the palmar and back of hand to be involved; the rash may have an elevated border and nearby nails may be affected.

Tinea pedis
Tinea pedis (athlete's foot) thrives in warm humid conditions and is most common in young adult men. It is caused by T rubrum and T interdigitale. The fungal spores can last for a long time, so walking barefoot in communal changing rooms and sharing towels can result in infection.
Athlete's foot usually occurs between the toes and can be dry with scaling or moist with maceration of the toe webs. The skin is red and itchy.
Variants of tinea pedis are:

  • Moccasin type: appears on soles, heels and lateral borders of the feet, this usually affects both feet and is common in people with circulation disorders.
  • Inflammatory/bullous type: blisters develop on the sole, instep and in between the toes.
  • Ulcerative type: infection spreads to dorsum and plantar surfaces of foot, often with bacterial infection.

Diagnosis of all of the above conditions is confirmed by taking a thorough history of the rash, clinical examination in good light and, if in any doubt, by taking skin scrapings for microscopy and culture.

Tinea unguium
Tinea unguium (fungal nail infection) is also known as onychomycosis and is common with increased age. Again, it often results from untreated tinea pedis/manuum, or following injury to the nail. Causative organisms include T rubrum and
T interdigitale. One or more nails may be affected in various ways - in lateral onychomycosis a yellow or opaque streak appears at one side of the nail; subungual hyperkeratosis presents with scaling under the nail; the end of the nail lifts up and crumbles in distal onychomycosis; flaky white patches on top of the nail plate are suggestive of superficial white onychomycosis; and in proximal onychomycosis yellow spots appear in the lunala of the nail.
Candida infection generally results from a paronychia and starts near the nailfold; the nail may eventually lift off its bed and is tender to touch. The diagnosis is confirmed with nail clippings.

Other forms of fungal skin infections

  • Tinea incognito is named due to the changed clinical appearance of the rash due to inappropriate treatment - often with topical steroids.
  • Tinea nigra affects the soles of the feet, appearing brown on white skin and black on dark skin.
  • Tinea versicolor is also known as pityriasis versicolor. This is a common yeast infection of the trunk caused by the fungus Malassezia furfur. Flaky discoloured patches appear on the trunk, neck and arms. The patches may be pink, brown or paler. This rash is common in hot humid climates and frequently recurs in the summer.

Self-help
It is generally agreed that simple advice can help people to improve healing and reduce the risk of infection to others. For example, those with athlete's foot should wear open footwear if possible, if not they should wear cotton socks and change them daily. It is also helpful to avoid walking barefoot in communal changing rooms. For all fungal conditions avoid sharing towels and make sure that showers, baths and floors are cleaned regularly at home, particularly if walking around barefoot. There is no need for children to miss school when tinea capitis is diagnosed.(1)

Treatment
As a rule it is generally agreed that treatment should be commenced while awaiting clinical results, especially if the likelihood of fungal infection is high.
Most minor fungal infections can be eradicated with topical antifungals agents. Dermatophytoses respond well to topical clotrimazole, miconazole, ketoconazole and terbinafine.
Combination preparations with corticosteroid are not recommended unless the rash is severely inflamed.(2)
Treatment for athlete's foot, ringworm and groin infections should be given for one to four weeks depending on the preparation given, and it is generally thought that in ringworm and groin infections treatment should be continued for one to two weeks following the resolution of the rash (however, there is no evidence to support this).(3)
Yeasts respond well to the above preparations plus topical nystatin. In particular, pityriasis versicolor often responds to selenium sulphide 2.5% shampoo applied neat to the rash.(3)
Oral antifungals such as griseofulvin, terbinafine and itraconazole are prescribed for more extensive disease, or when topical therapy has failed. These medications should be used cautiously because of their side- effect profile and lack of safety data in the elderly and children. Currently, griseofulvin is the only medication of this type that is licensed for children and adults.(4)
Topical treatment with clotrimazole and miconazole is considered safe for use in pregnancy and breastfeeding, but oral antifungals are not. Furthermore, men should be advised not to father a child within six months of completing oral antifungals agents because they can disturb chromosomes and cell division.(5)
If clinical signs have settled there is no need for review, but you may wish to check on the progress of the patient especially if waiting for clinical microbiology and culture of nail clippings or skin scrapings. Very often the patient does not comply with the treatment, so it is worth checking this before starting alternative treatment or referring to secondary care. Nevertheless, consider referral to a specialist if there is diagnostic uncertainty, if there has been no response to treatment, if the infection is severe or the patient is
immunocompromised.

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References

  1. Roberts BJ, Friedlander SF. Tinea capitis: a treatment update. Paediatr Ann 2005;34:191-200.
  2. Erbagci Z. Topical therapy in dermatophytoses: should corticosteroids be included? Am J Clin Dermatol 2004;5:375-84.
  3. Prodigy. Clinical Knowledge Summaries. Full guidance, skin and nail. Available from: http://www.prodigy.nhs.uk
  4. British National Formulary (50th edition). London: British Medical Association and Royal pharmaceutical Society of Great Britain; 2005.
  5. Schaefer C, editor. Drugs during pregnancy and lactation. Amsterdam: Elsevier Science; 2001.

Resources
Prodigy
W: www.prodigy.nhs.uk
Dermnet
W: www.dermnetnz.org