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Reactions to dermatophyte infections highlighted

June 08 2015

A recent study highlights the extraordinary range of unusual reactions to dermatophyte infection, Tinea capitis is the most common dermatophyte infection in children, with the highest incidence in children ages 3 to 7 years. In this study from Istanbul (Demir & Karadag, 2015), over a 6 month period, dermatophytid reactions were detected in 13 of the 19 children (68%) aged from 2 to 12 years. Seven (36.84%) had eczematous patches or plaques and three (15.8%) had papules, two (10.5%) eczematous lesions, papules, and pustules and one (5.3%) an angioedema-like reaction. In all cases, dermatophytid reactions were observed before the initiation of therapy. The authors speculate that these ‘id reactions’ are much more common than realised.

Professor Roderick Hay of the International Foundation for Dermatology comments: “The clinical manifestations of all infections are partly determined by characteristics of the invading organisms, such as the production of virulence factors, and partly by the innate or acquire immune response of the host. Dermatophyte or tinea infections are no exception. Many of the commonest infections such as tinea pedis caused by Trichophyton rubrum are strikingly mild in appearance showing a minor degree of scaling. There is some evidence that in these infections the immune response is down-regulated. By contrast in other dermatophyte infections there is a fierce response and lesions become very inflamed, raised and pustular. In hair bearing sites this is known as a kerion and it is associated with an active T cell mediated immune response.

The other reactions seen in dermatophyte infections are known as id reactions which are non-infective rashes that do not contain fungus but represent an allergic response to a dermatophyte infection often at a distance from the site of the rash. This rash spontaneously disappears when the infection settles, with or without treatment. But it may also be triggered by treatment".

The two main types of id reaction are:

1 A widespread eruption of small follicular papules – small raised bumps – which are in groups or diffusely scattered. This often seen with kerion and is thought to be due to immune complex deposition following release of circulating fungal antigen.

2 An eczematous vesicular (tiny blisters) form of an id, usually affecting the toe web spaces and fingers. This rash is characteristically associated with very inflammatory forms of tinea pedis, usually caused by T. interdigitale.

“There are also rarer forms of dermtophyte id reaction that include erythema nodosum or erythema multiforme, raised itchy or painful lumps or patches. These occur in other fungal infections such as coccidioidomycosis or histoplasmosis. Again they follow deposition of circulating immune complexes.”

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