title: Dermoscopic findings in scalp psoriasis and seborrheic dermatitis; two new signs; signet ring vessel and hidden hair.
abstract: BACKGROUND
  Psoriasis and seborrheic dermatitis are both chronic erythemato-squamous dermatoses that can involve the scalp. It may be difficult to differentiate these two diseases when there is isolated scalp involvement. Recently, trichoscopy is commonly used to differentiate noncicatricial alopecias including psoriasis and seborrheic dermatitis that can lead to telogen effluvium (TE).
  
  
  OBJECTIVE
  The objective of this study is to evaluate the trichoscopic figures that may help to differentiate scalp psoriasis and seborrheic dermatitis.
  
  
  METHODS
  Thirty one with scalp psoriasis and 112 patients with seborrheic dermatitis were enrolled. Trichoscopic examinations were performed using a videodermatoscope (MoleMax 3(®)). Trichoscopic findings of scalp psoriasis and seborrheic dermatitis were compared with each other, with 100 healthy individuals and with other noncicatricial alopecias including female androgenetic alopecia (FAGA) (n: 138), male androgenetic alopecia (n: 63), FAGA of male pattern (FAGA.M) (n: 5), alopecia areata (39), TE (n: 22) and trichotillomania (n: 4).
  
  
  RESULTS
  Atypical red vessels, red dots and globules (RDG), signet ring vessels (SRV), structureless red areas and hidden hairs (HH) were statistically more common in psoriasis while twisted red loops and comma vessels (CV) in seborrheic dermatitis. RDG were considered as the characteristic videodermatoscopic figure for psoriasis and arborizing red lines and CV for seborrheic dermatitis. In comparison with previous reports, our study yielded two new trichoscopic structures supporting the diagnosis of psoriasis; HH and SRV. Besides, according to our study, CV were described for the first time in seborrheic dermatitis and considered to be specific for seborrheic dermatitis.
  
  
  CONCLUSIONS
  This study confirmed that trichoscopy might be useful in differentiating scalp psoriasis and seborrheic dermatitis from each other and from other noncicatricial alopecia with three trichoscopic structures as HH, SRV and CV.
authors: Department of Dermatology, Muş Bulanık Government Hospital, Muş, Turkey.
authors: Melike
authors: M
authors: Kibar
authors: Department of Dermatology, Dokuz Eylül University School of Medicine, İzmir, Turkey.
authors: Şebnem
authors: Ş
authors: Aktan
authors: Department of Biostatistics, Eskişehir Osmangazi University School of Medicine, Turkey.
authors: Muzaffer
authors: M
authors: Bilgin
keywords: Dermatoscopy; dermoscopy; psoriasis; seborrheic dermatitis; trichoscopy
references: J Am Acad Dermatol. 2006 Nov;55(5):799-806
references: 17052485
references: Br J Dermatol. 2011 Mar;164(3):652-6
references: 21155753
references: J Cutan Pathol. 1985 Oct;12(5):412-25
references: 2932481
references: Am J Clin Dermatol. 2004;5(3):205-8
references: 15186200
references: An Bras Dermatol. 2011 Nov-Dec;86(6):1061-71; quiz 1072-4
references: 22281892
references: Am J Dermatopathol. 1979 Fall;1(3):199-214
references: 543520
references: J Am Acad Dermatol. 2004 Nov;51(5):811-3
references: 15523365
references: Arch Dermatol. 2006 Jun;142(6):808
references: 16785400
references: Arch Dermatol. 2007 Dec;143(12):1612
references: 18087028
references: Arch Pathol. 1967 Nov;84(5):443-50
references: 6054609
references: Semin Cutan Med Surg. 2004 Mar;23(1):39-45
references: 15095914
references: Hautarzt. 1979 Sep;30(9):478-83
references: 161301
references: Dermatology. 2006;212(1):7-18
references: 16319467
references: Clin Dermatol. 2007 Nov-Dec;25(6):524-8
references: 18021888
references: Arch Dermatol. 1972 Oct;106(4):503-6
references: 4116898
references: J Am Acad Dermatol. 2008 Aug;59(2):268-74
references: 18550207
references: J Dermatol. 2011 Jan;38(1):71-5
references: 21175759
references: Skin Res Technol. 2013 Feb;19(1):e60-4
references: 22220807
references: Am J Clin Dermatol. 2001;2(3):159-65
references: 11705093