Tinea capitis (scalp ringworm)
Infections may be passed from person to person (so-called anthropophilic, in which man is the primary host) or acquired from animals (zoophilic). Several different species of fungi may be responsible, predominantly Microsporum and Trichophyton species, and can be identified by their varied characteristics on microscopy and culture. Species that invade only the inside of the hair shaft are termed endothrix infections, whereas those that invade both the inside and the outside of the hair shaft are responsible for ectothrix infections. The disease is most prevalent in children and usually presents with areas of scaling and alopecia, with a varying degree of inflammation. There may be associated cervical lymphadenopathy. Some species of dermatophyte induce a very inflammatory, pustular reaction, which may lead to scarring and permanent alopecia. However, this is fortunately relatively rare with modern treatment regimens, in which full regrowth of hair is the norm.
Treatment of tinea capitis is aimed at eradicating the organism to prevent the spread of infection and minimize scarring. Established infections cannot be treated topically and oral therapy is required. In many countries, including the UK, griseofulvin remains the only licensed oral antifungal agent for use in tinea capitis in children. Although only weakly fungistatic, griseofulvin is effective in the treatment of most varieties of tinea capitis, but may need to be given in high doses over a prolonged period. Each case should be monitored to ensure adequate treatment and eradication of the organism. Traditionally this has been done using Wood’s light examination, but this is only viable in cases due to species that fluoresce (e.g., Microsporum infections). An increasing number of cases in the UK and North America today are due to the emergence of Trichophyton tonsurans, a non-fluorescent endothrix species. Treatment response therefore has to be followed mycologically, by sending specimens to the laboratory. Mycological cure should be the gold standard of treatment.
In recent years the azoles itraconazole, ketoconazole, and fluconazole, and the allylamine terbinafine have become available for systemic use. Many studies have demonstrated that these agents have at least equal efficacy to griseofulvin in a variety of types of tinea capitis, and treatment times are often shorter. Although these agents are more expensive, shorter treatment regimens may help compliance and reduce the spread of infection.
Over the past decade, the use of intermittent or pulsed treatment regimens using fluconazole or itraconazole have been explored. This treatment strategy is based on the long half-life of the drugs in keratin. Such regimens do not appear to confer any benefit in terms of cure rates, but may reduce the total cost of treatment.
There are variations in the response of different dermatophyte species to the different antifungal agents, and treatment should be tailored accordingly. Overall, griseofulvin appears superior in the clearance of Microsporum infections, but newer agents appear more effective against Trichophyton. However, so far no agent has been shown to achieve a 100% cure rate, which remains the ultimate objective of any treatment strategy.
Ectothrix infections are generally caused by Microsporum species, most notably the zoophilic M. canis or the anthropophilic M. audouinii, and almost always occur in children. Griseofulvin remains the treatment of choice at a dose of 10–20 mg/kg/day, but clearance may be slow and treatment should be continued for as long as necessary, which is at least 6 weeks, but may be 12–16 weeks, and monitored as outlined above. Itraconazole may be considered an alternative, although there are licensing restrictions in some countries.
Endothrix infections, most commonly with T. tonsurans or T. violaceum, are more prevalent in children, but may occasionally occur in adults (usually the contacts/carers of children). Higher-dose regimens of griseofulvin tend to be required to achieve cure. The newer azoles and terbinafine appear to achieve cure more rapidly (usually in 4 weeks). In adults with tinea capitis due to Trichophyton species, terbinafine 250 mg/day for 4 weeks is the treatment of choice. Although unlicensed in children, the current British National Formulary gives the dosing schedule for terbinafine in tinea capitis, in recognition of its widespread use (<20 kg, 62.5 mg/day; 20–40 kg, 125 mg/day; >40 kg, 250 mg/day). Current evidence suggests that either this or itraconazole should become the treatment of choice in children with Trichophyton infections.
Topical antifungal creams and shampoos are sometimes used in conjunction with oral therapy, with the aim of reducing the time that the patient is infectious.
In the current urban epidemics of T. tonsurans, asymptomatic infection in household contacts is posing a significant problem in re-infection/relapse, and there is merit in screening all family members (including adults) where practical.
Ketoconazole or selenium sulphide shampoos may reduce infectivity.