Tinea Capitis

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http://emedicine.medscape.com/article/1091351-overview

Epidemiology

Found in the soil, on animals, or on humans (geophilic, zoophilic, anthropophilic)

Tinea Capitis is predominantly caused by Trichophyton sp in US, causing an endothrix infection where spores exist within the hair shaft. This fungi is typically transmitted indirectly from person to person, with asymptomatic individuals as carriers. Spores can live on combs, couches, clothing, sheets, hats, etc for long periods of time, facilitating indirect transmission.

Microsporum sp is the most common cause of tinea in other parts of the world. M canis tinea capitis is typically spread by contact with dogs and cats.

In the US, prevalence of Tinea Capitis among inner-city school-aged (typically ages 3 to 9 years) children is 3-8%. The incidence of tinea capitis is greater in African Americans, which is thought to be due to increased coiling of the hair shaft. Tinea is the second most frequently reported skin disease in the US, second to acne. Worldwide incidence has increased over the past 30 years [1].

 

Clinical Presentation

The clinical presentation of Tinea Capitis is quite variable and may include any of the following:

  • patchy alopecia,
  • scale of seborrhea-like flaking throughout the scalp,
  • erythema,
  • pustules,
  • black dots showing that the hair broke off at the follicular orifice,
  • tenderness,
  • pruritus,
  • lymphadenopathy.

Studies have shown that occipital adenopathy has a positive predictive value of 84% for culture proved tinea capitis [2]. 

 

Differential Diagnosis

Because the presenting symptoms of tinea capitis are of such a wide variety, the differential is broad. Possibilities include:

Alopecia areata

Trichotillomania

Seborrheic dermatitis

Atopic dermatitis

Contact dermatitis

Psoriasis

Systemic Lupis Erythematosus

Pityriasis amiantacea

Bacterial folliculitis

Kerion

It is also important to distinguish dermatophytosis from pityriasis versicolor and candidiasis, as these make up the three most common of superficial fungal infections.

 

Diagnosis

Wood lamp – used since 1925; emits a long wavelength of UV radiation; helps diagnose variety of dermatologic conditions based on quality of fluorescence; now obsolete in US because the spores of Trichophyton sp do not fluoresce under UV light.

Microscopic confirmation using KOH preparation – KOH preserves fungal components while destroying squamous cells. Look for branching hyphae to confirm dermatophyte infection.

Fungal culture is gold standard technique for diagnosis. Obtain samples by vigorously rubbing moistened cotton swab over scalp. The sample is placed on a dermatophytic medium containing Sabouraud dextrose agar with chloramphenicol to inhibit bacterial growth and cycloheximide to inhibit saprophytic fungi. Culture is more sensitive than KOH prep but may take several weeks to become positive.

However, some studies have concluded that it is reasonable to prescribe empiric therapy based on symptoms alone if an inner city child presents with occipital or posterior auricular adenopathy associated with scaling, alopecia, or pruritus [2, 3]. 

 

Treatment

Systemic antifungal therapy is necessary because the dermatophyte is at the root of the hair follicle and thus not accessible by topical treatments. However, the addition of adjunct topical treatment does decrease transmissibility. Selenium Sulfide 2.5% shampoo can also be used as an adjunct to kill spores and decrease the spread – it is often recommended that other household members use this shampoo even if asymptomatic.

Griseofulvin – choice of treatment in patients with Microsporum tinea capitis; long history of safe use in children

-        20 to 25 mg/kg/day for 6 to 12 weeks if microsize formation

-        10 to 15 mg/kg/day for 6 to 12 weeks if ultramicrosize formulation

Terbinafine – better for Trichophyton species; duration of therapy is shorter

-        10 to 20 kg child – 62.5 mg/day for 2 to 4 weeks

-        20 to 40 kg child – 125 mg/day for 2 to 4 weeks

-        >40 kg child – 250 mg/day for 2 to 4 weeks

Itraconazole

-        3 to 5 mg/kg/day for 4 to 6 weeks

Fluconazole

-        6 mg/kg/day for 3 to 6 weeks

 

Complications

Kerion – severely inflammatory form of tinea capitis that often leads to scarring and permanent hair loss; treat with griseofulvin; culture and systemic antibiotics are unnecessary

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dermatologyoasis.net

 

References

  1. Elewski BE. Tinea Capitis: A Current Perspective. Journal of the American Academy of Dermatology. 2000; 42(1):1-20.
  2. Friedlander SF et al. Use of the Cotton Swab Method in Diagnosing Tinea Capitis. Pediatrics. 1999; 104(2):276-279.
  3. Smith, Michael. Tinea Capitis. Annals of Pediatrics. Feb. 1996.
  4. Stein DH. Tineas - Superficial Dematophyte Infections. Pediatrics in Review. 1998; 19:368-372.
  5. Friedlander S.F. et al. Terbinafine in the Treatment of TrichophytonTinea Capitis. Pediatrics Vol 109 No. 4  page 602. April 2002
  6. Fleece D. Griseofulvin Versus Terbinafine in the Treatment of Tinea Capitis: A Meta-analysis of Randomized Clinical Trials.  Peidatrics November 2004
  7. Shy R. Tinea Corporis and Tinea Capitis. Pediatrics in Review May 2007
  8. Kelly B. Superficial Fungal Infections.  Pediatrics in Review. April 2012

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