Background: The frequency of different types of alopecia is not clearly reported in recent studies.
Objective: To analyze the frequency of the types of alopecia in patients consulting at specialist hair clinics (SHC) and to assess for global variations.
Methods: Multicenter retrospective study including data from patients evaluated at referral SHC in Europe, America, Africa and Australia.
Results: A total of 2,835 patients (72.7% females and 27.3% males) with 3,133 diagnoses of alopecia were included (73% were non-cicatricial and 27% were cicatricial alopecias). In all, 57 different types of alopecia were characterized. The most frequent type was androgenetic alopecia (AGA) (37.7%), followed by alopecia areata (AA) (18.2%), telogen effluvium (TE) (11.3%), frontal fibrosing alopecia (FFA) (10.8%), lichen planopilaris (LPP) (7.6%), folliculitis decalvans (FD) (2.8%), discoid lupus (1.9%) and fibrosing alopecia in a pattern distribution (FAPD) (1.8%). There was a male predominance in patients with acne keloidalis nuchae, dissecting cellulitis and FD, and female predominance in traction alopecia, central centrifugal cicatricial alopecia, FFA, TE, FAPD and LPP.
Conclusion: AGA followed by AA and TE were the most frequent cause of non-cicatricial alopecia, while FFA was the most frequent cause of cicatricial alopecia in all studied geographical areas.
Keywords: Alopecia; Alopecia areata; Androgenetic alopecia; Epidemiology; Folliculitis decalvans; Frontal fibrosing alopecia; Hair diseases; Lichen planopilaris; Telogen effluvium.