🩺 Non-Scarring (Most Common)
• Alopecia areata: well-circumscribed round/oval patches, normal skin, exclamation point hairs, autoimmune
• Tinea capitis: scaling, broken hairs (black dots), ± kerion (boggy pustular plaque), Trichophyton tonsurans most common
• Telogen effluvium: diffuse shedding 3-5 months after stressor (fever, surgery, illness)
• Trichotillomania: irregular patchy loss, broken hairs of varying length, compulsive hair pulling
⚠️ Scarring (Cicatricial) Alopecia (Rare)
• Discoid lupus, lichen planopilaris, folliculitis decalvans
• Incontinentia pigmenti: X-linked dominant (female), vesicles → verrucous → hyperpigmented swirls, alopecia (scarring)
• Permanent hair loss due to follicle destruction
📋 Other Causes
• Traction alopecia: tight braiding, styling → frontal/temporal hairline
• Congenital: aplasia cutis (scalp defect), nevus sebaceous (yellow-orange plaque, pre-malignant, remove before adolescence)
• Loose anagen syndrome: easily pulled hairs, young blonde girls
• Androgenetic alopecia: male/female pattern hair loss, may begin adolescence
🔬 Diagnostic Tools
• Hair pull test: >3-6 hairs indicates active shedding
• KOH preparation: tinea (hyphae)
• Culture (fungal)
• Wood's lamp: green fluorescence in Microsporum canis (uncommon; T. tonsurans non-fluorescent)
• Scalp biopsy for scarring alopecia
📌 Decision strategy: Scaling + broken hairs → tinea capitis. Round smooth patches without scale → alopecia areata. Irregular broken hairs with varying length → trichotillomania. Diffuse shedding 3 months after stressor → telogen effluvium.