Clinical, Dermoscopic, and Mycological Characteristics of Tinea Capitis in Children

Overview

Tinea capitis is a common dermatophyte infection of the scalp in children aged 0-9 years .The prevalence of tinea capitis in Egypt is 0.4% and higher in public than private schools, Boys were more affected than girls according to children by 5:1 ratio , It is more prevalent in those who live in urban areas, large families, low socioeconomic level, crowded living conditions and immunocompromised people . Tinea capitis is caused by dermatophyte fungi Trichophyton and Microsporum genera. These fungi are classified as: anthropophilic, zoophilic, and geophilic according to the route of infection. These fungi invade the hair shaft in two routes: ectothrix and endothrix . T.tonsurans and T.violaceum are reported to be the most common cause of tinea capitis

Clinical types of tinea capitis include : scaly type (characterized by fine scaling and circular alopecia), black dot (characterized by non-inflammatory patches with broken-off, swollen hair stubs), tinea agminate (patchy alopecia with scattered pustules or low-grade folliculitis), kerion (painful, boggy, inflammatory masses with alopecia, often confused with bacterial abscess) and favus (scutula, mousy odor) . Tinea incognito (steroid modified tinea) refers to dermatophytosis that has lost their usual clinical appearance due to the use of steroids. The main clinical feature of dermatophyte scalp infections is the appearance of scaling of the scalp skin, which is associated with a variable degree of inflammation and itching . In some cases, the infection closely resembles seborrheic dermatitis or dandruff of the scalp. A pathognomonic feature is hair loss; hair often breaks a few millimeters or more above the skin surface. Broken or infected hairs are also slightly swollen and have a dull appearance . Trichoscopy is a non-invasive and very useful technique for the diagnosis and follow-up of hair and scalp disorders. The presence of certain trichoscopic features allows accurate identifying of tinea capitis. In tinea capitis, specific signs can be seen like comma hair, corkscrew hair, bar code-like hair and zigzag hair . In tinea incognito trichoscopic finding include erythema, scaling, bent hair, Morse code hair, and micropustules . Mycological examination was first performed using Potassium Hydroxide(KOH) to confirm the diagnosis of tinea capitis where the patients with positive KOH were considered to have endothrix when observing arthroconidia inside the hair shaft and ectothrix when observing arthroconidia outside the hair shaft. The fungal culture also done to accurately recognize the organism through inoculation of samples on Sabouraud medium agar (SDA) with and without chloramphenicol(nonspecific medium) . And Dermasel medium agar act as specific medium. The increase in antifungal resistance has recently been observed worldwide and resistant strains of the dermatophytes T. rubrum and T. indotineae have spread globally, causing outbreaks of extensive, difficult to treat infections , so we need rapid and reliable diagnostic tools that provide clues regarding the causative organisms.