Dermoscopic Findings in Scalp Psoriasis and Seborrheic Dermatitis: Two New Signs; Signet Ring Vessel and Hidden Hair

In 2015, a study involving 31 patients with scalp psoriasis and 112 patients with seborrheic dermatitis was conducted to identify trichoscopic figures that could differentiate between the two conditions. The study found that 'signet ring vessels' and 'hidden hairs' were more common in psoriasis, while 'twisted red loops' and 'comma vessels' were more common in seborrheic dermatitis. These findings introduced two new trichoscopic structures supporting the diagnosis of psoriasis and described 'comma vessels' for the first time in seborrheic dermatitis. The study concluded that trichoscopy could be useful in differentiating scalp psoriasis and seborrheic dermatitis from each other and from other noncicatricial alopecia.