Nonscarring hair loss in well demarcated patches due to immune mediated inflammation of hair follicles

Epidemiology:- Prevalence: 1 in 1000 people- Age: mostly in people < 30 years- Sex: ♂ = ♀

Etiology:- Immune mediated inflammation and disruption of anagen phase hair follicles → well defined patches of nonscarring hair loss- A trigger factor (emotional stress, infections, pregnancy, etc.) may precede some cases - Family history in up to 20% of cases

Clinical features:- Abrupt onset (within weeks)- Smooth, circular, well defined patches of hair loss without scarring (Bland scalp)- Exclamation point hairs- Various patterns of distribution- Nail involvement (up to 40% of cases): nail pitting, onycholysis, Beau lines, etc.

Diagnostics: usually clinical, biopsy rarely necessary + histology, trichogram

Differential diagnosis:- Trichotillomania: Compulsive pulling out of one's own hair → ill defined patchy hair loss and hairs of different lengths. - Tinea capitis: The affected areas of scalp are scaly compared to the smooth hair loss of alopecia- Secondary syphilis: patchy hair loss → moth-eaten appearance of scalp- Brocq pseudopelade: scarring

Treatment:- Intralesional steroids (triamcinolone)- Topical immunotherapy: DCP (diphenylcyclopropenone) or SADBE (squaric acid dibutyl ester)- PUVA treatment (Psoralen + UVA)