Dermoscopy and Scalp Biopsy in the Hair Transplant Evaluation

17 Dermoscopy and Scalp Biopsy in the Hair Transplant Evaluation

Aron G. Nusbaum and Antonella Tosti

Summary

While the majority of patients seeking hair restoration surgery have androgenetic alopecia, surgeons must be able to properly identify patients with other etiologies of hair loss. An invaluable tool to aid in scalp examination that is fairly easy to learn is dermoscopy, which involves the interpretation of magnified scalp images to identify changes not visible with the naked eye and can quickly provide the clinician with important diagnostic clues. This modality can detect characteristic features of many hair loss conditions and, for example, aids in the differentiation of scarring from nonscarring alopecia, androgenetic alopecia from telogen effluvium or alopecia areata incognita, and classic alopecia areata from other patchy alopecias. When findings are equivocal or a scarring alopecia is suspected, scalp biopsy is indicated, and dermoscopy-guided localization is recommended as it has shown to significantly increase diagnostic yield.

Keywords: dermoscopy-guided localization nonscarring alopecia scarring alopecia alopecia areata incognita classic alopecia areata telogen effluvium patchy alopecias interfollicular vascular patterns

Key Points

•An invaluable, noninvasive tool to aid in scalp examination is dermoscopy, which involves interpreting magnified scalp images to identify changes that are not visible with the naked eye and can quickly provide the clinician with important diagnostic clues regarding the etiologies of alopecias.

•When clinical or dermoscopic findings are equivocal, scalp biopsy should be performed not only for hair loss diagnosis but also for determining disease activity.

•Dermoscopy-guided localization to select biopsy sites is recommended, as this has been shown to significantly increase diagnostic yield.

17.1 Introduction

Hair restoration surgeons will invariably encounter patients with different types of alopecia. With regard to performing surgery, some of these conditions require special consideration and others may have relative or absolute contraindications. In hair restoration, as in any medical discipline, a correct diagnosis is essential for formulating a proper treatment plan, especially when surgery is being considered.

While the overwhelming number of individuals seeking hair restoration surgery have androgenetic alopecia (AGA), special subsets such as diffuse unpatterned alopecia (DUPA) are critical to recognize. In addition, nonandrogenetic cases of both scarring and nonscarring alopecia can present with subtle features and can also coexist with or mimic AGA. It is clear that increased awareness of these etiologies is needed along with training in scalp examination and use of ancillary tools such as dermoscopy and scalp biopsy.

Scalp examination begins by looking for a recognizable pattern as seen in patients with AGA, and suspicion should immediately arise if these patterns are not discernable. An invaluable, noninvasive tool to aid in scalp examination is dermoscopy or trichoscopy which can be performed using a video microscope with greater than ×20 magnification (a common tool utilized in most hair transplant clinics) or a dermatoscope attached to a digital camera or smartphone.1 Dermoscopy involves interpreting magnified scalp images to identify changes that are not visible with the naked eye and can quickly provide the clinician with important diagnostic clues (Table 17.1). This modality can detect characteristic features of many hair loss conditions and, for example, aids in the differentiation of scarring from nonscarring alopecia, AGA from telogen effluvium (TE) or alopecia areata incognita (AAI), and classic alopecia areata (AA) from other patchy alopecias. While a diagnosis can often be made solely on physical examination and dermoscopy, when findings are equivocal or a scarring alopecia is suspected, scalp biopsy should be performed. Biopsies are important not only in hair loss diagnosis but also in determining disease activity of certain disorders. When scalp biopsy is indicated, dermoscopy-guided localization is recommended, as it has shown to significantly increase diagnostic yield.¹^,²

Table 17.1 Classical dermoscopic findings in hair loss disorders

Dermoscopic finding	Description	Associated hair loss disorder
Variable hair shaft miniaturization >20%	>20% of hairs with decreased caliber of varying degrees	Androgenetic alopecia
Black dots	Black dots visible within follicular ostia	Alopecia areata Trichotillomania
Exclamation point hairs	1–3 mm short hairs broader at the distal end	Alopecia areata
Follicular keratotic plugging	Keratotic debris occluding follicular ostia	Discoid lupus erythematosus
Hair tufting (2–4 hairs)	Hair groups exiting from same ostium	Lichen planopilaris
Hair tufting (≥6 hairs)	Hair groups exiting from same ostium	Folliculitis decalvans
Peripilar casts	keratotic cuffs surrounding the proximal hair shafts at their emergence	Lichen planopilaris Frontal fibrosing alopecia Discoid lupus erythematosus Traction alopecia (active)
Peripilar gray-white halo	Gray-white circle around hairs at ostium	Central centrifugal cicatricial alopecia
Peripilar sign	Brown halo surrounding hairs at ostium	Androgenetic alopecia
Red dots	Pink-red polygonal structures surrounding and within ostia	Discoid lupus erythematosus
White patches	Sclerotic, white areas devoid of follicular ostia	Scarring alopecia
Yellow dots	Small, yellow to yellow-pink round or polycyclic dots	Alopecia areata Androgenetic alopecia Trichotillomania

17.2 Dermoscopy of the Normal Scalp

In order to properly detect the dermoscopic features seen in patients with hair loss pathology, it is important to recognize the normal scalp findings seen in patients without alopecia, or in the case of AGA, the unaffected donor fringe. The normal scalp is composed of evenly distributed follicular units containing one to four hairs and vellus hairs, the latter of which represent no more than 10 to 20% of the total number of hairs.3 An interfollicular vascular pattern can also be appreciated with capillaries in the dermal papilla seen as fine, red, hairpin-shaped loops and the deeper dermal plexus visualized as larger-caliber arborizing red lines.⁴ In patients with skin of color or with chronic solar damage, one can appreciate adjoining brown rings in a honeycomb network representing melanocytic pigmentation, as well as pinpoint white dots, which denote the ostia of sweat ducts and/or empty follicles in exogen.⁵

17.3 Dermoscopy of Nonscarring Alopecia

17.3.1 Androgenetic Alopecia

Diagnostic features of AGA include hair diameter variability (anisotrichosis), the presence of more than six short regrowing hairs in the frontal scalp, and single hair-bearing follicles. One of the most distinguishing features in affected areas of AGA is hair shaft diameter variability exceeding 20% (Fig. 17.1a), with thinner hair shafts and decreased number of hairs within follicular units as compared to the occiput. Surrounding the emergence of hair shafts, one may see a brown halo “peripilar sign” which has been shown to correlate with perifollicular inflammation.⁶ Irregularly distributed yellow dots of varying shapes and sizes can also be been, especially in advanced cases (Fig. 17.1⁷ The yellow dots in AGA tend to have an oily appearance which may correlate with a prevalence of sebum in the follicular ostia. In DUPA, a subtype of AGA, the previously described miniaturization process is observed also in dermoscopy of the donor zone, signifying an unstable donor not suitable for transplantation.⁸

Fig. 17.1 (a) Hair shaft diameter variability >20% indicative of androgenetic alopecia (AGA). (b) Yellow dots at the follicular ostia with variable hair shaft miniaturization in a patient with AGA.

17.3.2 Alopecia Areata

In its most common form, AA is easily recognized by patchy, nonscarring hair loss with preservation of follicular ostia. More important for hair restoration surgeons is to be aware that this condition can present clinically in a diffuse form which may be difficult to distinguish from AGA. In addition, AA may occur superimposed on AGA.

In AA, dermoscopic findings include black dots and broken hairs (which correspond to fragmented hair shafts) as well as exclamation mark hairs (short fractured hairs, 1–3 mm in length with the distal end broader in diameter than the proximal segment) and coudability hairs (hairs of normal length with a narrowed proximal portion). Black dots are present in more than 40% of patients and correlate with disease activity as do exclamation mark hairs.⁹ Yellow dots are observed in both AA and AGA. In AA, they may be empty or contain broken hairs (Fig. 17.2) or short regrowing hairs, which often appear as clustered short vellus hairs in contrast to hairs of varying degrees of miniaturization which are present in AGA.