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Tinea%20capitis%20(pediatric) Diagnosis
Assessment
Patterns of Clinical Infection
- Host T-lymphocyte response determines clinical infection patterns
- Diffuse or patchy, fine, white, adherent scales on the scalp resembling dandruff
- There are tiny, perifollicular pustules and/or hair stubs from the scalp
- Patient has areas of noninflammatory hair loss that are well demarcated; hairs are broken off at the follicular orifice and debris left at the opening appears as a black dot
- Color of “dot” will depend on hair color
- Caused by T tonsurans, T soudanense, T violaceum, M audouinii
- Patient has circular patches with hair loss and fine scaling which is dull grey in color
- Greying is caused by the spores covering the affected hair
- Intense inflammation manifests as single or multiple boggy, tender areas of alopecia with pustules on and/or in surrounding skin
- Hypersensitivity to fungus may form a boggy, indurated, tumor-like mass that exudes pus and referred to as kerion
- Discrete pustules or scabbed areas without scaling or significant hair loss
- Pustules result from superimposed bacterial infection
- An inflammatory variant characterized by yellow cup-shaped crusted lesions called scutula
- Commonly seen in the Middle East and North Africa, caused by T schoenleinii
Laboratory Tests
Microscopy
- Provides the most rapid means of diagnosis but may not always show positive in affected patients
- Scalp scales and/or hair are mounted in 10-30% potassium hydroxide (KOH) solution, gently heated and viewed under light or fluorescence microscope
- Positive results reveal hairs and scales invaded by spores and/or hyphae
- Large-spored endothrix pattern chains of large spores within hair (T tonsurans, T violaceum)
- Large-spored ectothrix (T verrucosum, T mentagrophytes)
- Small-spored ectothrix randomly arranged in masses inside and on the surface of the hair shaft (M canis, M audouinii)
- Allows accurate identification of organism but results may take up to 4 weeks (6 weeks for T verrucosum, T violaceum and T soudanense)
- Use of Sabouraud agar with 1 or more plates with cycloheximide is recommended
- Options for growth media that can be used include Kimmig fungal agar and other agars that contain antibiotics and cycloheximide (eg Mycosel® agar)
- Results may be positive even when microscopy is negative
- Necessary in hair fungal infections to identify the source of infection and verify the infecting species
- A noninvasive in vivo imaging technique that may aid in the diagnosis of tinea capitis, especially in patients with black dot pattern
- Used for rapid initial assessment and when mycological tests are unavailable
- May also be used when choosing a suitable sampling site and for treatment monitoring, in combination with ultraviolet light
- Useful for certain ectothrix infections (eg M canis, M audouinii, M rivalieri)
- If present, will cause hair to fluoresce bright green
- T tonsurans, T rubrum and T mentagrophytes, which cause tinea capitis (depending on the region), does not fluoresce
- Eg conventional polymerase chain reaction (PCR) with subsequent species identification by sequencing, enzyme-linked immunosorbent assay (ELISA), microarray, blot, real-time PCR, matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry
- Highly sensitive and specific, and significantly faster compared to KOH preparation and culture
- Currently the only methods capable of species identification from clinical material
- Histologic examination of biopsies with staining may be considered in post-treatment patients with a negative mycological test result especially those with deep dermatophytosis
