Trichoscopy performed with a handheld dermoscope or a videodermoscope became an indispensable tool in differential diagnosis of hair and scalp diseases. Current research is focusing on trichoscopy of: 1) non-cicatricial alopecia, 2) cicatricial alopecia, 3) hair shaft disorders, and 4) inflammatory scalp diseases. This review summarizes current knowledge in these four fields of research. In all non-cicatricial alopecias presence of empty follicular openings is a common trichoscopy finding. In alopecia areata black dots and micro-exclamation mark hairs and tapered hairs correlate with disease activity, whereas yellow dots and vellus hairs correlate with disease severity. In androgenic alopecia trichoscopy shows hair shaft thickness heterogeneity, multiple thin and vellus hairs, yellow dots, perifollicular discoloration, and predominance of follicular units with only one hair. These features predominate in the frontal area. In all forms of cicatricial alopecia, trichoscopy shows milky-red or ivory-white areas lacking follicular openings. In classic lichen planopilaris trichoscopy shows perifollicular inflammation, tubular perifollicular scaling, elongated, concentric blood vessels and "classic white dots", which merge to form white areas. Frontal fibrosing alopecia shows mild perifollicular scaling. Folliculitis decalvans is characterized by tufted hairs, large follicular pustules with emerging hair shafts and perifollicular starburst pattern hyperplasia. In dissecting cellulitis characteristic findings are "3D" yellow dots imposed over dystrophic hairs, large, yellow amorphous areas and pinpoint white dots with a whitish halo. Trichoscopy is particularly useful to diagnose hair shaft abnormalities in trichorrhexis nodosa, trichorrhexis invaginata, monilethrix, pili torti, and pili annulati. The method may be also useful in diagnosing inflammatory scalp diseases. In discoid lupus erythematosus trichoscopy shows large arborizing vessels and large hyperkeratotic folliculilar yellow dots. Trichoscopy of scalp psoriasis shows regularly distributed twisted and lacelike blood vessels, whereas in seborroic dermatitis thin arborizing vessels may be observed. In tinea capitis trichoscopy shows comma, corkscrew and zigzag hairs. Examination tinea capitis may be facilitated by UV-light enhanced trichoscopy (UVET). In conclusion, trichoscopy is a non-invasive method which may be applied in differential diagnosis of most hair and scalp diseases.

Objective:Establishing the trichoscopy criteria of female androgenic alopecia (FAGA).Design:Trichoscopy images were retrospectively evaluated.Setting:Dermatologic hospital-based clinic and private practice offices.Patients and methods:One hundred and thirty-one females (59 with androgenic alopecia, 33 with chronic telogen effluvium (CTE), 39 healthy controls). The diagnosis was based on clinical examination and confirmed by histopatology.Main Outcome Measure:Trichoscopy results obtained in frontal, occipital and both temporal areas of the scalp under a 20-fold and 70-fold magnification, including average hair thickness, number of 'yellow dots' and vellus hairs, number of hairs in one pilosebaceous unit and percentage of follicular ostia with perifollicullar hyperpigmentation.Results:Average hair thickness in frontal area versus occiput was, respectively, 0.061 ± 0.008 mm versus 0.058 ± 0.007 mm in healthy controls, 0.047 ± 0.007 mm versus 0.052 ± 0.008 mm in androgenic alopecia and 0.056 ± 0.007 mm versus 0.053 ± 0.009 mm in CTE. Mean percentage of thin hairs (< 0.03 mm) in androgenic alopecia was 20.9 ± 12% and was significantly higher than in healthy controls (6.15 ± 4.6%, P < 0.001) or in CTE (10.4 ± 3.9%, P < 0.001). The number of yellow dots, pilosebaceous units with only one hair and with perifollicular hyperpigmentation was significantly increased in androgenic alopecia. Classification and Regression Tree Analysis was performed to establish diagnostic criteria for FAGA.Conclusion:FAGA may be differentiated from CTE based on trichoscopy criteria. Major criteria are ratio of (1) more than four yellow dots in four images (70-fold magnification) in the frontal area, (2) lower average hair thickness in the frontal area compared to the occiput and (3) more than 10% of thin hairs (below 0.03 mm) in the frontal area. Minor criteria encompass increased frontal to occipital ratio of (1) single-hair pilosebaceous units, (2) vellus hairs and (3) perifollicular discoloration. Fulfillment of two major criteria or one major and two minor criteria allows to diagnose FAGA based on trichoscopy with a 98% specificity.

Differential diagnosis of trichotillomania is often difficult in clinical practice. Trichoscopy (hair and scalp dermoscopy) effectively supports differential diagnosis of various hair and scalp diseases. The aim of this study was to assess the usefulness of trichoscopy in diagnosing trichotillomania. The study included 370 patients (44 with trichotillomania, 314 with alopecia areata and 12 with tinea capitis). Statistical analysis revealed that the main and most characteristic trichoscopic findings of trichotillomania are: irregularly broken hairs (44/44; 100% of patients), v-sign (24/44; 57%), flame hairs (11/44; 25%), hair powder (7/44; 16%) and coiled hairs (17/44; 39%). Flame hairs, v-sign, tulip hairs, and hair powder were newly identified in this study. In conclusion, we describe here specific trichoscopy features, which may be applied in quick, non-invasive, in-office differential diagnosis of trichotillomania.

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Importance: Nodular melanoma (NM) is a rapidly progressing potentially lethal skin tumor for which early diagnosis is critical.Objective: To determine the dermoscopy features of NM.Design: Eighty-three cases of NM, 134 of invasive non-NM, 115 of nodular benign melanocytic tumors, and 135 of nodular nonmelanocytic tumors were scored for dermoscopy features using modified and previously described methods. Lesions were separated into amelanotic/ hypomelanotic or pigmented to assess outcomes.Setting: Predominantly hospital-based clinics from 5 continents.Main Outcome Measures: Sensitivity, specificity, and odds ratios for features/models for the diagnosis of melanoma.Results: Nodular melanoma occurred more frequently as amelanotic/hypomelanotic (37.3%) than did invasive non-NM (7.5%). Pigmented NM had a more frequent (compared with invasive non-NM; in descending order of odds ratio) symmetrical pigmentation pattern (5.8% vs 0.8%), large-diameter vessels, areas of homogeneous blue pigmentation, symmetrical shape, predominant peripheral vessels, blue-white veil, pink color, black color, and milky red/pink areas. Pigmented NM less frequently displayed an atypical broadened network, pigment network or pseudonetwork, multiple blue-gray dots, scarlike depigmentation, irregularly distributed and sized brown dots and globules, tan color, irregularly shaped depigmentation, and irregularly distributed and sized dots and globules of any color. The most important positive correlating features of pigmented NM vs nodular nonmelanoma were peripheral black dots/globules, multiple brown dots, irregular black dots/globules, bluewhite veil, homogeneous blue pigmentation, 5 to 6 colors, and black color. A model to classify a lesion as melanocytic gave a high sensitivity (Ͼ98.0%) for both nodular pigmented and nonnodular pigmented melanoma but a lower sensitivity for amelanotic/hypomelanotic NM (84%). A method for diagnosing amelanotic/hypomelanotic malignant lesions (including basal cell carcinoma) gave a 93% sensitivity and 70% specificity for NM.Conclusions and Relevance: When a progressively growing, symmetrically patterned melanocytic nodule is identified, NM needs to be excluded.