Background: Alopecia areata is a nonscarring hair loss that usually causes round patches of baldness, but alopecia areata incognita (AAI) and diffuse alopecia areata (DAA) can cause a diffuse and acute pattern of hair loss. Objective: To analyze the clinical, trichoscopic, histological, and therapeutic features of AAI and DAA. Methods: The study was designed to include data of patients with histological diagnosis of AAI and DAA enrolled in our Hair Disease Outpatient Consultations. Results: DAA had a greater involvement of the parietal and anterior-temporal regions, while AAI manifested itself mainly in the occipital-parietal regions. The most frequent pattern was empty yellow dots, yellow dots with vellus hairs, and small hair in regrowth, but the presence of pigtail hair was found almost exclusively in those with AAI. In cases of DDA, the finding of dystrophic hair and black dots was more frequent. The most frequent trichoscopic sign in both diseases was the presence of empty yellow dots, which, however, were described in a higher percentage in cases of DAA. The diseases have a benign course and are responsive to topical steroid therapy. Conclusions: Trichoscopy is very important for the differential diagnosis between the 2 diseases and to select the best site for biopsy. In the presence of diffuse hair thinning, these entities must be considered.

Summary: Background: Recently, platelet‐rich plasma (PRP) injection has been proposed as a potential adjuvant therapy to treat androgenetic alopecia.Aims: Investigate the efficacy, tolerability, and clinical improvement of PRP for the treatment of female AGA.Patients/Methods: A total of 10 female patients affected by AGA and not responding to treatment with minoxidil and/or oral antiandrogens were enrolled. The clinical improvement was evaluated by pull test, global photographs, and Trichoscan at weeks 9, 12, and 24, and hair measurements were performed at baseline and 12 and 24 weeks after the first session.Results: After 24 weeks, the median relative percentage change (%RC) for all the parameters of hair density was mostly positive. After 12 weeks, the medium hair diameter in frontal area showed a significant increase (%RD = 12.5, with P‐value < .05), and after 24 weeks (%RD = 14.6, P‐value < .05), the vellus relative change instead showed a decrease, especially in the front and the central area, while for the vertex, the decrease was mainly visible at the end (−6.6%). No adverse events were reported.Conclusion: Platelet‐rich plasma injections have a positive therapeutic effect on hair density and hair diameter improvement.