Hair Disorders in Children

Hair Basics - Tiny Follicle Facts

• Hair Cycle (Pediatric): Phases:
  • Anagen (active growth): 2-6 yrs, ~85-90% hairs.
  • Catagen (involution): 2-3 wks, <1%.
  • Telogen (resting): 2-3 mths, ~10-15%; then Exogen (shedding).

  ⭐ Newborn anagen phase is shorter, leading to physiological telogen effluvium (hair shedding in first few months).

• Classification: Etiology (Congenital/Acquired), distribution (Localized/Diffuse), scarring (Scarring/Non-scarring).
• Diagnostic Approach:
  • History: Onset, duration, pattern, family hx, systemic symptoms, hair care.
  • Clinical Exam: Scalp (inflammation, scale), Hair Pull Test (>10% hairs = positive), specific hair signs (exclamation (!) mark hairs, black dots, broken hairs).
  • Wood's Lamp: For Microsporum spp. (green fluorescence) in Tinea Capitis.
  • Trichoscopy: Non-invasive. AA (yellow/black dots, ! hairs), Tinea Capitis (comma, corkscrew, barcode hairs), Trichotillomania (varied length broken hairs, flame hairs).
  • Scalp Biopsy: For scarring alopecias, diagnostic uncertainty.

Non-Scarring Alopecias - Patchy Problems Parade

⭐ 'Exclamation mark' hairs (short, broken, proximally tapering) are pathognomonic for Alopecia Areata.

• Alopecia Areata (AA): Autoimmune; well-demarcated patches; ophiasis pattern (band-like loss at scalp margins). Trichoscopy: yellow dots, black dots, broken hairs. Rx: Topical/intralesional corticosteroids, minoxidil, anthralin. Severe: Systemic steroids, JAK inhibitors.
• Tinea Capitis: Fungal infection. India: T. violaceum, T. tonsurans. Ectothrix/Endothrix. Types: Black dot, grey patch, kerion (boggy, inflamed), favus (cup-shaped scutula). Dx: KOH, culture. Rx: Griseofulvin 20-25 mg/kg/day for 6-8 weeks; Terbinafine (if T. tonsurans).
• Telogen Effluvium (TE): Diffuse shedding ~3 months post-trigger (fever, stress, ↓nutrition). Positive hair pull test (>10% hairs in telogen). Reassurance, address trigger.
• Trichotillomania (TTM): Compulsive hair pulling. Bizarre patterns, varied hair lengths. Trichoscopy: perifollicular hemorrhages, v-sign, flame hairs. Rx: SSRIs, behavioral therapy.
• Traction Alopecia: Due to tight hairstyles. 'Fringe sign' (sparing of short hairs along frontal/temporal hairline). Reversible early; later, scarring. Rx: Looser hairstyles.

Hair Shaft & Scarring - Strand & Scar Stories

Hair Shaft Defects:

• Congenital Alopecias:
  • Aplasia Cutis Congenita (ACC): Localized skin absence, often scalp; membranous type with 'hair collar' sign.
• Scarring Alopecias (Rare in Children):
  • Irreversible follicular destruction (e.g., Lichen Planopilaris, Folliculitis Decalvans).
• Growth/Color Disorders:
  • Hypertrichosis: ↑Hair growth (non-androgenic). Pediatric causes: drugs (minoxidil), syndromes.
  • Hirsutism: ↑Male-pattern hair (androgenic). Pediatric causes: CAH, PCOS, tumors.
  • Poliosis: Localized white hair patch. Associations: Piebaldism, Waardenburg, Tuberous sclerosis.

⭐ Menkes kinky hair syndrome, an X-linked recessive disorder of copper metabolism, presents with Pili Torti, sparse hypopigmented hair, and severe neurodegeneration.

High‑Yield Points - ⚡ Biggest Takeaways

• Tinea capitis (often T. tonsurans) is the most common pediatric alopecia.
• Alopecia areata presents with exclamation mark hairs and non-scarring patches.
• Telogen effluvium: diffuse shedding 2-3 months post-trigger (e.g., fever).
• Traction alopecia results from chronic tension from tight hairstyles.
• Trichotillomania: compulsive hair pulling leading to bizarre hair loss patterns.
• Loose anagen syndrome: easily, painlessly pluckable anagen hairs, common in fair-haired girls.
• Netherton syndrome: key feature is trichorrhexis invaginata (bamboo hair).