In the 14 cases of seborrheic dermatitis, scales were the main characteristic findings in all patients (100%) (Fig. 3c). Arborizing blood vessels (Fig. 3d), which appeared as branching red lines and were best viewed when the camera probe was angled tangentially, were observed in five patients (35.7%) (Table 3).
In the 11 cases of tinea capitis, all patients showed comma hairs (a specific marker of tinea capitis). Scales were detected in nine patients (81.8%) (Fig. 4a). No exclamation mark hairs or corkscrew hairs were observed in any of the lesions (Table 3).
In the three cases of DLE, hyperkeratotic follicular plugs (Fig. 4b), arborizing and tortuous vessels (Fig. 4b), white and brown dyschromia (Fig. 4c), and reduction in follicular ostia (Fig. 4c) were observed in the three patients. Follicular red dots (Fig. 4b) distributed regularly in and around the follicular openings as red to pink-red, round dots, were observed in one patient (33.3%) and these dots were not influenced by pressure. Blue-gray dots (Fig. 4d) were observed, with a speckled pattern of distribution along the patch of alopecia, in two patients (66.6%). Scales (Fig. 4d) were also observed in one patient (33.3%) (Table 3).
Comparing patients with nonscaly hair loss scalp diseases, AA and AGA, it was found that clustered vellus hair, black dots, tapering hair, and yellow dots are specific to AA, whereas more than 20% hair diameter diversity and peripilar sign were specific for AGA. However, white dots and a honeycomb pattern were features of both diseases (Table 2).
Comparing patients with scaly scalp diseases, such as psoriasis, seborrheic dermatitis, tinea capitis, and DLE, it was found that interfollicular red dots were specific for psoriasis, whereas follicular red dots were specific for DLE. Arborizing blood vessels were features of DLE, seborrheic dermatitis, and psoriasis, in descending frequency. Comma-like hair was a specific feature of tinea capitis. Brown dyscromia, reduction of follicular ostia, and blue dots were specific features of DLE (Table 3).
The present study was carried out on the most common scalp diseases encountered in everyday dermatological practice and may have clinical diagnostic similarities. In the past few years, dermoscopy has been used successfully in the evaluation of different hair disorders either as a diagnostic device or as a useful instrument to gain a better insight into their pathogenesis 9.
In this study, cases with AA showed clusters of vellus hairs in 74.4% of patients. The pigmented hairs of Egyptians facilitate the detection of short vellus hairs by dermoscopy. Vellus hairs represent hair regrowth; thus, they indicate the nondestructive nature of AA and are considered a sensitive marker of AA. Our results are in agreement with those of Inui et al. 10, who reported vellus hairs in 72.7% of patients and confirmed the presence of vellus hairs as a characteristic dermoscopic finding of AA, and they correlated negatively with disease activity and severity.
Black dots may be considered as remnants of exclamation mark hairs or broken hairs, providing a sensitive marker not only for disease activity but also for the severity of AA 11,12. Broken hairs were observed in 58.1% of AA patients in this study, which is consistent with Inui et al.10. They represent hairs that are fractured at different distances from the scalp secondary to inflammation in the hair bulb 13. However, Karadag et al. 11 observed broken hair in 57.1% of AA patients, documenting them not only in AA but also to a lesser extent in patients with primary cicatricial alopecia and AGA, suggesting that broken hairs are a suggestive but not an indicative feature of AA. The black dots of AA occur mainly in black-haired individuals, including Egyptians, and this finding has never been used for the diagnosis of AA in white populations. This difference may be attributed not only to hair color but also to cuticle resistance. Indeed, it was reported that cuticles of black-haired individuals fall as large pieces while retaining their original shape under extension stress, whereas hair cuticles of white populations tend to collapse to form small fragments 10.
The tapering hair shafts toward the follicles in alopecia patches (exclamation mark hairs) were more readily perceived using dermoscopy than by the naked eye in 58.1% of the patients. Exclamation mark hair is important in the diagnosis of AA as they indicate the presence of the lymphocytic inflammatory infiltrate affecting the hair bulb and, thus, producing a thinner hair shaft. In agreement with the present study, it is considered as a specific marker for AA 14. Exclamation mark hair helps in differentiating AA from tinea capitis as this finding was not observed in patients with tinea capitis 15. Our results are in agreement with those of Inui et al. 10 and Karadag et al. 11, who reported exclamation mark hairs in 31.7 and 42.9% of AA patients, respectively.
Moreover, coudability hairs were found in 9.3% of the patients, which were better visualized by dermoscopy than by the naked eye. The coudability hairs represent normal-looking hairs tapered at the proximal aspect and occur in perilesional hairs of normal length. They correspond to a premature rapid transition from anagen to catagen, causing hair shaft narrowing at the follicles. In addition, it was suggested that some black dots are remnants of coudability hairs. Thus, the coudability hairs are considered as a clinical indicator of the disease activity of AA 10,16.
Yellow dots were detected in 51.1% of our patients, which likely represents distension of the affected follicular infundibulum with keratinous material and sebum 13. Yellow dots are very characteristic and have been observed in over 95% of European patients 8 and in 60% of Asian patients 10. Few yellow dots were observed in African-American patients of skin phototypes V and VI in Brazil, which is consistent with our finding 13. It is believed that the reduced contrast of the pigmented scalp of Egyptian patients and the yellowish color of yellow dots may make observation of these findings difficult. Another explanation is that yellow dots were initially described as pathognomonic of diffuse AA, being highly emphasized for the diagnosis of the diffuse form 13. Although Inui et al. 10 reported that yellow dots are sensitive but not specific in AA because they can be seen in other hair loss diseases such as AGA, yellow dots were not found in the present AGA cases. Moreover, they reported that yellow dots possibly indicate the coincidence of AGA and enlargement of the sebaceous glands caused by common end-organ hypersensitivity to androgen 11,17.
White dots were observed in 32.5% of AA and 28.5% of AGA cases. The presence of white dots represents eccrine pores, which could be seen by dermoscopy in normal scalp 18. Karadag et al. 11 detected white dots in about 15.3% of AGA patients. In contrast, Ross et al.2 could not observe white dots in their patients with AGA. A honeycomb pattern was observed in 25.5% of AA and 31.4% of AGA cases. This is in agreement with Ross et al.2, who detected a honeycomb pattern in 18.7 and 26% of AA and AGA cases, respectively. De Moura et al.13 reported that a honeycomb pigment pattern appears to be a marker of chronic persistent or slowly progressive AA. Honeycomb pigment may result from chronic sun exposure of the balding scalp 2,11.
In all patients with AGA, we counted the number of hairs and calculated the percentage of apparently thin hairs. When the percentage of thin hairs was more than 20%, we defined it as significant for AGA, where hair diameter diversity reflects hair follicle miniaturization and corresponds to vellus transformation of the follicles 19. In the present study, it was considered as a specific feature as it was not elicited in the other groups. Meanwhile, it was accepted as an essential but not a specific finding of androgenic alopecia because it was reported in diffuse AA and primary cicatricial alopecia as well 20,21. This is not in disagreement with the results of the present study as diffuse AA cases were not among the present cases.
In early AGA, it is common to observe peripilar brown depressions around the follicular ostium described as peripilar signs that are linked to perifollicular lymphocyte infiltration 20 as perifollicular inflammation may activate melanocytes in the outer root sheath and cause peripilar pigmentation 17. They were detected in 45.7% of cases of AGA in this study. This was less than that reported previously in a white population (90%) 20 and Asian individuals (66%) 17 possibly because the Egyptian skin color conceals slight peripilar pigmentation.
Moreover, they reported that yellow dots possibly indicate the coincidence of AGA and enlargement of the sebaceous glands caused by common end-organ hypersensitivity to androgen 11,17.
In scalp psoriasis, red dots represent twisted red loops that correspond to tortuous capillaries in the dermal papilla as twisted loops occur in epidermal hypertrophy with a psoriasiform pattern 22. In this study, red dots were observed in all patients with psoriasis but twisted red loops could not be observed by dermoscopic magnification (×10). Our result is in agreement with that of Ross et al.2 as they reported that striking arrays of red dots were observed in all cases with psoriasis at lower magnification, but these dots appeared as multiple, relatively evenly spaced, twisted red loops at higher magnification. However, Kim et al.23, who observed twisted red loops and red dots in patients with psoriasis using dermoscopic magnification (×10), reported that the vascular patterns of the scalp lesions could be observed better with the application of ultrasound gel. In this study, other signs of vasculature such as arborizing red lines were observed only in 14.2% of patients with psoriasis and scales were detected in all the patients in accordance with other studies 24–26.
In scalp seborrheic dermatitis, arborizing blood vessels, which indicate markedly dilated capillaries in hyperplastic rete ridges, were observed in 35.7% of our patients, whereas no twisted loops or red dots were observed. Our results are in agreement with those of Ross et al.2 and Kim et al.23, who observed arborizing blood vessels in 62 and 49% of patients with seborrheic dermatitis, respectively; however, they observed twisted loops in 19 and 22% of patients with seborrheic dermatitis, respectively. Scales were observed in all patients (100%) with seborrheic dermatitis.
Patients with tinea capitis showed broken hairs that were characterized by a sharp slanting end, homogenous thickness, and pigmentation of hair shaft. Their diameter and morphology allow us to differentiate them from exclamation mark hairs present in AA, which are characterized by a blunt end with hair shaft tapering and brightening toward the follicular orifice 1. Our result is in agreement with that of Slowinska et al.15, who observed broken hairs in tinea capitis. Comma hairs were observed in all patients (100%) with tinea capitis as a result of subsequent cracking and bending of a hair shaft filled with hyphae in tinea capitis 27. Our result is in agreement with that of other studies 27,28 that detected comma hairs in all patients with (100%) tinea capitis and considered them as a specific dermoscopic marker for tinea capitis. Scales were also observed in 81.8% of patients with tinea capitis. In this study, corkscrew hairs were absent in tinea capitis. It could not be detected in dark-skinned patients including Egyptian, Ethiopian, and Congolese patients infected with Trichophyton violaceum27.
All patients with scalp DLE showed hyperkeratotic follicular plugs. Keratin plugs correlate histologically with follicular hyperkeratosis 29. White and brown dyschromia, corresponding to dermal fibrosis (scarring) and pigment incontinence, respectively 29, were observed in 100% of patients with DLE. Our results are in agreement with those of Tsai et al.29, who observed white and brown dyschromia in DLE. Reduction of follicular ostia as a result of fibrosis was observed in all patients (100%). The reduction in the number of follicular ostia is a typical finding in cicatricial alopecias and has been reported previously in DLE 30. White scales were observed in 33.3% of patients with DLE. Our results are in agreement with those of Ross et al.2 and Tsai et al.29, who observed hyperkeratotic perifollicular white scales in some patients with DLE 29. Follicular red dots that correspond to widened infundibula plugged by keratin and surrounded by dilated vessels and extravasated erythrocytes were observed in 33.3% of patients with DLE. This pattern is probably easily identified on dermoscopy owing to the presence of atrophic epidermis and may be a specific dermoscopic feature in DLE and helps the clinician to differentiate DLE from other diseases causing cicatricial alopecia 31. In contrast, earlier studies 32,33 reported the absence of perifollicular erythema in DLE and this was attributed to the presence of dilated papillary dermal vessels without erythrocytes extravasation in pathological examination. Arborizing and tortuous vessels were observed in the interfollicular scalp between the red dots in all patients with DLE. They may correspond to papillary dermal dilated vessels. Blue-gray dots were observed in 66.6% of our patients with DLE with a speckled pattern that may represent interface dermatitis and the subsequent pigment incontinence in the papillary dermis of follicular and interfollicular epidermis.
Hair and scalp dermoscopy is a fast and noninvasive technique that allows identification of hair and scalp diseases in everyday practice. Dermoscopy may be useful in the differential diagnosis of common hair and scalp disorders such as AA, AGA, and tinea capitis. Specification of vascular patterns by dermoscopy can be valuable for the clinical diagnosis and differentiation of scalp psoriasis and seborrheic dermatitis. Further large studies correlating dermoscopic findings with histopathological features are required to improve the clinical significance of dermoscopy and to establish clear trichoscopy criteria for the diagnosis of specific hair loss disorders.
Conflicts of interest
There are no conflicts of interest.
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Keywords:© 2014 Egyptian Women's Dermatologic Society
alopecia areata; androgenetic alopecia; dermoscope; discoid lupus erythematosus; scalp disorders; scalp psoriasis; seborrheic dermatitis