Tinea%20capitis Diagnosis

• All specimens obtained (scalp scrapings, hair follicles) should undergo microscopy & culture, w/ causative organism identified

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