Non-Cicatricial Alopecias - Hair Today Gone Tomorrow
| Feature | Androgenetic Alopecia (AGA) | Alopecia Areata (AA) | Telogen Effluvium (TE) |
|---|---|---|---|
| Key Features | Gradual, patterned loss (Hamilton-Norwood/Ludwig); follicular miniaturization | Autoimmune; patchy/total loss (ophiasis); nail pitting; exclamation mark hairs | Acute, diffuse shedding 2-3 months post-trigger; +ve pull test |
| Histology | ↑Telogen hairs, miniaturized follicles, ↓anagen:telogen ratio | Peribulbar lymphocytic infiltrate ("swarm of bees") | ↑Telogen hairs (>20-25%); no significant inflammation |
| Treatment Pearls | Minoxidil, Finasteride (males), Spironolactone (females) | Corticosteroids (topical/IL/systemic), immunotherapy | Address trigger, reassurance, topical Minoxidil |
Cicatricial Alopecias & Hair Shaft - Scarred Scalps Snapped Strands
Permanent hair loss due to follicle destruction and scarring. Key types:
| Feature | Lichen Planopilaris (LPP) | DLE (Scalp) | Folliculitis Decalvans (FD) |
|---|---|---|---|
| Clinical | Perifollicular erythema/scaling. Frontal Fibrosing Alopecia (FFA) variant. | Erythematous plaques, atrophy, follicular plugging, dyspigmentation. | Chronic pustules, crusts. 'Tufted folliculitis' (polytrichia). |
| Histology | Lymphocytic interface/bulge infiltrate, perifollicular lamellar fibrosis, vacuolar alteration. Loss of sebaceous glands. | Epidermal atrophy, follicular plugging, interface dermatitis, thickened basement membrane, dermal mucin. | Early: neutrophilic perifollicular abscess. Late: lymphoplasmacytic infiltrate, plasma cells, fibrosis. |
| Distinguishing | Lonely hairs, loss of follicular openings. | Carpet tack sign. Photosensitivity. | Often S. aureus. Boggy, tender scalp. |
⭐ 'Tufted folliculitis' is characteristic of Folliculitis Decalvans.
Hair shaft defects (e.g., Trichorrhexis Nodosa) cause brittle hair, snapped strands, usually non-scarring.
Nail Infections & Anatomy - Fungal Fingers Toe Troubles
and paronychia)
- Nail Anatomy: Plate, bed, matrix (growth), nail folds (proximal/lateral), eponychium (cuticle), hyponychium.
- Onychomycosis (Tinea Unguium): Fungal nail infection.
Type Organism(s) Highlights Key Feature(s) DLSO T. rubrum (most common) Distal/lateral entry, subungual hyperkeratosis WSO T. mentagrophytes Superficial white patches on nail plate PSO T. rubrum, Candida (HIV assoc.) Proximal entry, cuticle; immunocompromised TDO End-stage of others Total nail destruction, thickened - Paronychia: Nail fold inflammation.
- Acute: Bacterial (S. aureus, Strep.). <6 wks. Rapid pain, erythema, pus. Tx: Warm soaks, antibiotics.
- Chronic: Candida albicans, irritants. >6 wks. Boggy, tender folds, nail dystrophy. Tx: Avoid irritants, antifungals.
⭐ Trichophyton rubrum is the most common dermatophyte causing onychomycosis worldwide.
Nail Disease & Tumors - Nail Clues Nasty Knots
-
Nail Psoriasis vs. Lichen Planus (LP):
Feature Psoriasis Lichen Planus (LP) Pitting Irregular, deep Fine, rare Onycholysis Common, "oil drop" Common Subungual Hyperkeratosis Common Common Pterygium Absent Present (dorsal, classic) 
-
Key Nail Lines & Associations:
- Beau's lines: Transverse grooves; severe illness, chemo.
- Mees' lines: Transverse white bands; arsenic, renal failure.
- Muehrcke's lines: Paired white bands (nail bed); hypoalbuminemia.
- Beau's lines: Transverse grooves; severe illness, chemo.
-
Other Important Changes:
- Clubbing: Lovibond angle >180°; lung disease, cyanotic heart disease.
- Koilonychia: Spoon nails; iron deficiency.
- Onycholysis: Nail plate separation from bed.
- Paronychia: Nail fold inflammation (acute/chronic).
- Onychomycosis: Fungal; thick, discolored.
- Clubbing: Lovibond angle >180°; lung disease, cyanotic heart disease.
-
Melanonychia Evaluation: (📌 ABCDEF rule for melanoma)
> ⭐ Hutchinson's sign (pigment on proximal/lateral nail fold) is a red flag for subungual melanoma. 
- Nail Tumors:
- Glomus tumor: TRIAD - severe pain, cold sensitivity, localized tenderness. Bluish.
- Subungual melanoma: Often melanonychia; check Hutchinson's sign.
High‑Yield Points - ⚡ Biggest Takeaways
- Alopecia Areata: Peribulbar lymphocytic infiltrate ("swarm of bees") is characteristic.
- Androgenetic Alopecia: Shows hair follicle miniaturization and ↑ telogen hairs.
- Lichen Planopilaris: Follicular interface dermatitis and fibrosis cause scarring alopecia.
- Tinea Capitis: Fungal elements (endothrix/ectothrix) in hair; PAS stain confirms.
- Nail Psoriasis: Oil spots, pitting, onycholysis; neutrophils in nail plate (Munro's).
- Onychomycosis: Fungal hyphae in nail plate/bed; PAS stain is diagnostic.
- DLE: May cause scarring alopecia with follicular plugging, interface changes.
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