Hair and Nail Disorders
Two appendages, two logics
Hair loss is classified as scarring versus nonscarring and focal versus diffuse. Nail disease is classified by which nail structure is involved (matrix, bed, fold, plate).
Concepts to master
- Androgenetic alopecia: patterned thinning, frontal in men, diffuse central in women; miniaturized hairs on trichoscopy.
- Alopecia areata: well-circumscribed smooth patches, exclamation-mark hairs, nail pitting; associated with autoimmunity.
- Telogen effluvium: diffuse shedding weeks after a trigger (illness, childbirth, medication); nonscarring and reversible.
- Scarring alopecias: lichen planopilaris, frontal fibrosing alopecia, and discoid lupus; loss of follicular ostia and permanent hair loss.
- Nail psoriasis: pitting, onycholysis, oil spots, and subungual hyperkeratosis.
- Onychomycosis: distal and lateral subungual pattern; confirm with KOH or culture before systemic therapy.
- Longitudinal melanonychia: consider subungual melanoma, especially with Hutchinson sign or a single dark band in an adult.
Traps
The most common error is treating presumed onychomycosis without confirmation - many dystrophic nails are psoriatic. Another is missing scarring alopecia, which requires early biopsy and urgent treatment to prevent permanent loss. Exclamation-mark hairs confirm alopecia areata but may be absent in chronic disease.
Rule of thumb
In any alopecia, first ask whether the follicular ostia are preserved. Preserved ostia mean nonscarring and potentially reversible; absent ostia mean scarring and irreversible, so biopsy early.