Tinea capitis vs Alopecia areata and trichotillomania
How to tell Tinea capitis and Alopecia areata and trichotillomania apart when a board question makes them look alike.
Tinea capitis is scaly fungal alopecia; alopecia areata is smooth autoimmune patches; trichotillomania is irregular broken hairs of different lengths.
Side by side
Tinea capitis causes scaly alopecia, broken hairs, black dots, kerion, and dermatophyte infection of scalp hair.
Alopecia areata causes smooth non-scarring patches with exclamation point hairs; trichotillomania causes irregular hair loss with hairs of varying length from pulling.
Dermatophytes invade hair shafts and scalp stratum corneum.
Alopecia areata is autoimmune hair bulb attack; trichotillomania is traction from repetitive hair pulling.
KOH hyphae, scale, black dots, and fungal culture support tinea capitis.
Exclamation point hairs support alopecia areata; broken hairs of varying lengths support trichotillomania.
The trap
Patchy hair loss overlaps, so scale/KOH, exclamation hairs, and hair-length irregularity separate them.
The repair move
For patchy alopecia, inspect scale, hair shafts, and KOH before naming the cause.
Try a free question
CoreA 7-year-old boy has 4 weeks of patchy hair loss with scaly, erythematous scalp and 'black dots' (broken hairs at the scalp surface). Posterior cervical lymphadenopathy is present. KOH preparation of hairs shows fungal hyphae within the hair shaft. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Tinea capitis. Tinea capitis is a dermatophyte (Trichophyton tonsurans most common in the US) scalp infection with scaling, hair breakage ('black dots'), and lymphadenopathy; treatment is oral antifungals (griseofulvin or terbinafine) because topical agents do not penetrate hair shafts.
Why the other choices are tempting
- B. Alopecia areata has smooth, non-scaly, well-circumscribed patches of complete hair loss with 'exclamation point' hairs.
- C. Trichotillomania has irregular patches with broken hairs of varying lengths from picking/pulling.
- D. Traction alopecia is at sites of chronic tension (hairline).
- E. Telogen effluvium is diffuse shedding without scaling.
Flashcards
Tap a card to flip it.
What microscopy supports tinea capitis?
KOH showing hyphae supports tinea capitis.
What hair finding supports alopecia areata?
Exclamation point hairs support alopecia areata.
Quick answers
What is the fastest way to tell Tinea capitis from Alopecia areata and trichotillomania?
Tinea capitis is scaly fungal alopecia; alopecia areata is smooth autoimmune patches; trichotillomania is irregular broken hairs of different lengths.
What is the key clue for Tinea capitis?
Tinea capitis causes scaly alopecia, broken hairs, black dots, kerion, and dermatophyte infection of scalp hair.
What is the key clue for Alopecia areata and trichotillomania?
Alopecia areata causes smooth non-scarring patches with exclamation point hairs; trichotillomania causes irregular hair loss with hairs of varying length from pulling.
What is the common trap with Tinea capitis vs Alopecia areata and trichotillomania?
Patchy hair loss overlaps, so scale/KOH, exclamation hairs, and hair-length irregularity separate them.