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Tinea capitis is the name used for infection of the scalp with a dermatophyte fungus. Hair can be infected with species of Trichophyton (abbreviated as T.) and Microsporum (M.).
Tinea capitis is most prevalent between three and seven years of age. It is slightly more common in boys than in girls. Infection by T. tonsurans may occur in adults.
Any race or ethnicity can be infected. There are geographical variations in the prevalent species causing the infection.
M. canis is the usual dermatophyte fungus to cause tinea capitis in New Zealand. This fungus is zoophilic and grows naturally on an animal rather than a human. M. canis tinea capitis is usually due to contact with an infected kitten or rarely an older cat or dog.
Other zoophilic fungi sometimes found to cause tinea capitis are:
In the United States, T. tonsurans has also become a common cause of tinea capitis; this is passed on from one person to another as it naturally infects humans (i.e. it is anthropophilic). It frequently causes no symptoms and is commonly found in adult carriers.
Other anthropophilic fungi sometimes found to cause tinea capitis are:
Dermatophyte fungi sometimes originate in the soil (geophilic organisms). These rarely cause tinea capitis:
Tinea capitis is classified according to how the fungus invades the hair shaft.
Ectothrix hair invasion is due to infection with M. canis, M. audouinii, M. distortum, M. ferrugineum, N. gypsea, M. nanum, and T. verrucosum. The fungal branches (hyphae) and spores (arthroconidia) cover the outside of the hair. Ectothrix infections can be identified by Woods light (long wave ultraviolet light) examination of the affected area the vet uses this to check your cat's fur. The fur fluoresces green if infected with M. canis.
Endothrix invasion results from infection with T. tonsurans, T. violaceum and T. soudanense. The hair shaft is filled with fungal branches (hyphae) and spores (arthroconidia). Endothrix infections do not fluoresce with a Wood light.
Favus does not occur in New Zealand. It is caused by T. schoenleinii infection, which results in honeycomb destruction of the hair shaft.
Anthropophilic infections such as T. tonsurans are more common in crowded living conditions. The fungus can contaminate hairbrushes, clothing, towels and the backs of seats. The spores are long-lived and can infect another individual months' later.
Zoophilic infections are due to direct contact with an infected animal and are not generally passed from one person to another.
Geophilic infections usually arise when working in infected soil but are sometimes transferred from an infected animal.
Tinea capitis may present in several ways.
Tinea capitis may result in swollen lymph glands at the sides of the back of the neck. Untreated kerion and favus may result in permanent scarring and bald areas.
It can also result in an id reaction, especially just after starting antifungal treatment.
Clinical types of tinea capitis
Tinea capitis is suspected if there is a combination of scale and bald patches. Wood light fluorescence is helpful but not diagnostic as it is only positive if the responsible organism fluoresces, and fluorescence is sometimes seen for other reasons.
Dermatoscopy/trichoscopy characteristically reveals:
Dermoscopy of tinea capitis
The diagnosis of tinea capitis should be confirmed by microscopy and culture of skin scrapings and hair pulled out by the roots (see laboratory tests).
Tinea capitis: Wood's light fluorescence
If the child has an anthropophilic infection, all family members should be examined for signs of infection. Brushings of scaly areas of the scalp should be taken for mycology. Sometimes it is best for the whole family to be treated whether or not the fungal infection is proven.
It is advisable for parents of classmates and other playmates to be informed so their children may be examined and treated if necessary. In some countries, infected children are not allowed to attend school. Elsewhere children with tinea capitis can attend school providing they are receiving treatment.
Carriers may have no symptoms. Treatment of carriers is necessary to prevent the spread of infection. Antifungal shampoo twice weekly for four weeks may be sufficient, but if cultures remain positive, oral treatment is recommended.
Suitable shampoos include these ingredients:
Tinea capitis requires treatment with an oral antifungal agent. Griseofulvin is probably the most effective agent for infection with M. canis but is no longer available in New Zealand. Trichophyton infections may successfully be eradicated using oral terbinafine, itraconazole or fluconazole for 4 to 6 weeks. However, these medications are not always successful, and it may be necessary to try another agent. Intermittent treatment may also be prescribed such as once-weekly dosages.
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