Table 1.
Important clinical findings of alopecias to aid in diagnosis.
| Type of hair loss | Loss of follicular ostia | Pattern | Scale | Erythema | Trichoscopy | Trichogram | Classic findings |
|---|---|---|---|---|---|---|---|
| Alopecia areata | No | Patchy, diffuse, or complete hair loss | No | None to mild | Yellow dots, exclamation mark hairs | Tapered hair | “Exclamation point” hairs, ± nail pitting, ± family history of AA |
| Anagen effluvium | No | Diffuse | No | No | Occurs days or weeks after inciting event | ||
| Androgenetic alopecia | No | Patchy, usually vertex or temporoparietal regions | No | No | Thin and vellus hairs, hair shaft thickness diversity, perifollicular pigmentation, yellow dots | Diversity of hair shaft thickness | Vellus hairs within patches, ↑ androgen levels, ± family history |
| Aplasia cutis congenita | No | Focal | No | No | Telangiectasia, radially oriented hair follicles with visible bulbs under translucent epidermis | Absent, thin or ulcerated overlying skin, surrounded by ring of dark, coarse hair “collar” | |
| Central centrifugal cicatricial alopecia | Yes | Patchy, starting at vertex | Yes | Yes | Peripilar gray/white halo, disrupted pigmented network | Hair loss gradually spreads centrifugally, ± family history | |
| Congenital atrichia and hypotrichosis | No, follicular agenesis | Diffuse | No | No | Complete hair loss by >2 years, isolated finding or feature of syndrome | ||
| Congenital triangular alopecia | No | Focal, often unilateral, temporal region | No | No | Vellus hairs, miniaturized terminal hair follicles, hair length diversity | Vellus hairs within patches, ± peripheral terminal hairs, does not improve with age | |
| Discoid lupus erythematosus | Yes | Patchy, diffuse | Yes | Yes | Yellow dots with radial, thick, arborizing vessels | Confluent erythema and scale, follicular plugging | |
| Female pattern hair loss | No | Diffuse, “Christmas tree pattern” on top of scalp | No | No | Yellow dots, single-hair pilosebaceous units, perifollicular hyperpigmentation | Often little to no evidence of androgen excess | |
| Lichen planopilaris | Yes | Patchy, diffuse | Yes | Yes | Perifollicular erythema and scales, scalp atrophy | ||
| Loose anagen syndrome | No | Diffuse | No | No | Rectangular black granular structures, solitary yellow dots, and >90% of follicular units with single hairs | Ruffled cuticle, absent root sheaths | Tend to occur in female infants, improves with age |
| Short anagen syndrome | No | Diffuse | No | No | Telogen hair with tipped point | Normal hair density, but with very short hairs | |
| Structural hair disorders | No | Diffuse | No | No | Features specific to different hair shaft abnormalities (107) | Fragmented hair shaft; increase hair breakage | Variation in hair texture and appearance, (+) hair tug test |
| Telogen effluvium | No | Diffuse | No | No | Increased percentage of clubbed hairs | Occurs approximately 3 months after inciting event or illness, (+) hair pull test if active disease | |
| Tinea capitis | Yes and no | Patchy | Yes | Yes | Black dot or “comma” hair, posterior cervical LAD, (+) KOH test | ||
| Traction alopecia | Yes and no | Patchy, usually temporal or frontomarginal regions | Yes | Yes | Fringe sign, history of grooming practices causing excessive scalp tension, ± folliculitis, (−) hair pull test | ||
| Transient neonatal hair loss | No | Focal | No | No | Improves with age | ||
| Trichotillomania | No | Patchy with irregular borders | None to mild | None to mild | Broken hairs, “V-sign,” tulip hairs | Various stages of hair regrowth, ± loss of eyebrow or lashes, (−) hair pull test, personal or family psychiatric history | |
LAD, lymphadenopathy; KOH, potassium hydroxide.