[Roles of dermoscopy in the diagnosis and differential diagnosis of scalp psoriasis and seborrheic dermatitis].

OBJECTIVE: To describe the dermoscopic patterns of scalp psoriasis and seborrheic dermatitis and explore the roles of dermoscopy in their diagnosis and differential diagnosis. METHODS: A total of 40 patients with scalp psoriasis (n = 20) and seborrheic dermatitis (n = 20) were recruited from Department of Dermatology, Peking Union Medical College Hospital from December 2013 to May 2014. They were examined both dermoscopically and histopathologically. And characteristic dermoscopic features were evaluated. Sensitivity, specificity, positive predictive value and negative predictive value were calculated for predefined dermoscopic criteria in relation to the diagnosis of two diseases. RESULTS: The most significant dermoscopic features of scalp psoriasis included dotted vessels (10/20, 50%), glomerular vessels (13/20, 65%), red loops (16/20, 80%), hairpin vessels (17/20, 85%), white scales (10/20, 50%) and punctate hemorrhages (12/20, 60%). In contrast, seborrheic dermatitis was characterized by arborizing vessels (16/20, 80%), atypical red vessels (13/20, 65%), featureless areas (20/20, 100%) and honeycomb pigment (9/20, 45%) (all P < 0.05). CONCLUSIONS: Scalp psoriasis and seborrheic dermatitis have different dermoscopic patterns. Dermoscopy may be valuable for clinical diagnosis and differential diagnosis of scalp psoriasis and seborrheic dermatitis.