Tinea%20capitis Diagnosis
Diagnosis
- All specimens obtained (scalp scrapings, hair follicles) should undergo microscopy & culture, w/ causative organism identified
Laboratory Tests
Microscopy
- Provides the most rapid means of diagnosis but may not always be positive in affected patients
- Scalp scales &/or hair are mounted in 10-30% potassium hydroxide (KOH) solution, gently heated & viewed under light or flourescence microscope
- Positive results reveal hairs and scales invaded by spores &/or hyphae
Causative Agents
- Large-spored endothrix pattern chains of large spores within hair (Trichophyton tonsurans, T violaceum)
- Large-spored ectothrix (T verrucosum, T mentagrophytes)
- Small-spored ectothrix randomly arranged in masses inside & on the surface of the hair shaft (Microsporum canis, M audouinii)
Dermoscopy (Trichoscopy)
- A noninvasive in vivo imaging technique that may aid in the diagnosis of Tinea capitis, especially in patients w/ black dot pattern
Culture
- Allows accurate identification of organism but results may take up to 4 weeks
- Use of Sabouraud agar w/ 1 or more plates w/ cycloheximide is recommended
- Results may be positive even when microscopy is negative
- Necessary in hair fungal infections to identify the source of infection & verify the infecting species
Wood’s Light Exam
- Useful for certain ectothrix infections (eg M canis, M audouini, M rifalieri)
- If present, will cause hair to fluoresce bright green
- T tonsurans which causes most Tinea capitis does not fluoresce