Clinical Notes : Dermatology

142. Kerion

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Tinea infections

"Tinea" refers to a skin infection with a dermatophyte (ringworm) fungus.

Depending on which part of the body is affected, it is given a specific name :

Sometimes, the name gives a different meaning :

  • Tinea versicolor is more accurately called pityriasis versicolor. This is a common yeast infection on the trunk.

  • Tinea incognita (often spelled incognito) refers to a tinea infection in which the clinical appearance has changed because of inappropriate treatment.

  • Tinea nigra is a mould infection (not a dermatophyte). It affects the palms or soles, which appear brown (on white skin) or black (on dark skin).

Clinical variants include :

  • Tinea imbricata

  • Majocchi granuloma

  • Kerion

  • Favus

 

What is Kerion ?

A kerion is an abscess caused by fungal infection.

It most often occurs on the scalp (tinea capitis), but it may also arise on any site exposed to the fungus such as face (tinea faciei) and upper limbs (tinea corporis).

It is often misdiagnosed as bacterial infection.

Kerion

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What causes Kerion ?

A kerion is caused by dramatic immune response to a dermatophyte fungal infection (tinea).

 

The most common fungi found in kerion are:

  • Microsporum canis

  • Trichophyton tonsurans

  • Trichophyton verrucosum

  • Trichophyton mentagrophytes

 

Trichophyton rubrum is not a common cause of kerion.

 

How is Kerion diagnosed ?

 

Suspicion is raised due to the typical appearance of a kerion.

Examination using a Wood lamp emitting long wavelength UVA may reveal yellow-green fluorescence if kerion is due to Microsporum canis, but is often negative even when this is the responsible organism because the inflammation obscures the presence of the fungus.

To confirm the diagnosis, scrapings and hair samples may be taken from the affected area for microscopy and fungal culture (laboratory tests for fungal infection).

A bacterial swab should be considered as secondary infection with bacteria is common.

 


Is Kerion contagious ?

 

Yes, fungal infection may be transmitted by kerion to other members of the household if they are in close contact, especially if sharing bedding and towels.

Combs and hairbrushes should be disinfected or discarded to prevent transmission of infection or re-infection.

As the fungus causing the kerion (e.g. M canis) is often residing on a household pet (e.g. kitten), family members may also be infected by direct contact with the animal.

What is the treatment of Kerion ?

 

Kerion should be treated by oral antifungal agents.

A course of 6-8 weeks of treatment is normally prescribed at minimum. 

 

Topical antifungal agents are not effective due to deep invasion of fungus into the hair follicle.

 

Antibiotics may be needed if there is bacterial infection present.

Antifungal shampoos containing ketoconazole or ciclopirox help to reduce the risk of spread of infection to others.

The hair normally grows back after the infection is treated, but sometimes hair loss is permanent, especially if the infection has been longstanding.

 
 
 

REFERENCES :

Kerion

DermNetNZ  (CCPL)

Dr Maneka Gnanasegaram

2012

Access

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The following oral meds are available in Ireland :

Terbinafine (Fungasil, Lamisil, Nailderm, Terbasil, Ternaf)

Fluconazole (Diflazole, Diflucan, Flucol, Fluconazole Actavis)

The following oral meds are not available in Ireland :

Itaconazole

Griseofulvin

The following shampoos are available in Ireland :

Selenium sulfide (Selsun)

Ketoconazole (Ketozol, Nizoral)

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