DLE of the scalp

The scarring alopecia of DLE is an LE-specific cutaneous lesion according to Gilliam’s classification of cutaneous LE.28 DLE is a cutaneous item in the SLICC criteria and is counted separately from non-scarring alopecia.1

Epidemiology

Scalp is the most common site affected by DLE, occurring in 30%–50% of reported cases.29–31 In its early stages, DLE lesions are only slightly inflammatory and non-scarring.25 However, as much as 60% of patients with scalp DLE continue to progress towards permanent and irreversible hair loss.32 It accounts for 30%–40% of all scarring alopecias combined33–35 and about 60% of all primary lymphocytic alopecias, making it the most common scarring alopecia in this subgroup.14 33 In a prospective cross-sectional study, the proportion of patients with scarring alopecia did not differ across LE subgroups (generalised DLE, localised DLE, systemic LE).31 Although scalp DLE is more frequent in women,31 32 35 there is an equal proportion of both sexes in terms of the tendency to develop scarring alopecia from DLE.31 The age of onset is usually between 20 and 40 years of age,14 30 33 35 and it is reported to be most prevalent among African–Americans.30 32 The presence of scarring alopecia in a patient with DLE portends a prolonged disease course.14 31

Pathology

The hallmark finding in cicatricial alopecias is fibrosis of the follicular structure, which is appreciated clinically as obscured follicular openings on the scalp.36 The scarring process usually begins with the inflammatory cells infiltrating the follicular bulge, a contiguous part of the outer root sheath located at the insertion point for the arrector pili muscle. This marks the bottom of the permanent portion of hair follicles and is also where the epidermal hair stem cells are located.14 Once replacement by fibrous tissue is established, hair loss is permanent and irreversible.36 37 Scarring alopecias are usually either (1) primary, in which the hair follicle is the main target of inflammation; or (2) secondary, if a separate disease process causes destruction of the nearby follicular structure.34 In 2001, the North American Hair Research Society proposed a classification scheme for the primary scarring alopecias based on the predominant inflammatory cell type on histology (lymphocytic, neutrophilic, mixed, non-specific).36 Scalp DLE serves as a model for studying the processes leading to primary lymphocytic cicatricial alopecias.37

Although the pathogenesis of scarring in DLE is not fully elucidated, several hypotheses can explain the processes leading to the collagenous transformation of the follicular structure in primary cicatricial alopecias.34 36 37 In scalp DLE, the most likely determinant of fibrosis is the aggregation of inflammatory infiltrates in the bulge area of the follicle where there is a high concentration of antigen-presenting Langerhans cells in close association with epithelial hair follicle stem cells.14 37 The aggregation of inflammatory infiltrates around the pilosebaceous junction also leads to the destruction of the sebaceous gland in DLE,14 a feature that is not usually present in acute or subacute cutaneous LE.31 When there is no sebum to regulate the outward movement of the hair, the shaft moves proximally perforating the bulbar region and inciting a foreign body granulomatous reaction that precipitates the scarring process.34 DLE lesions of the scalp are susceptible to Koebnerisation, increasing in number on sites frequently rubbed and scratched such as the scalp.14 Although ultraviolet light is a known trigger of cutaneous lupus erythematosus (CLE), interestingly, in one prospective cross-sectional study, sun-exposed alopecic patches of patterned hair loss and sites with prominent solar elastosis did not show an increased tendency to develop discoid lesions.31 Smoking has been found to worsen DLE on the scalp and to make the lesions more resistant to therapy.38

Clinical features

A panel of international experts recently proposed the following morphological features to distinguish DLE from other mimickers: (1) an erythematous to violaceous hue, (2) features of damage such as atrophic scarring and dyspigmentation, (3) follicular hyperkeratosis or plugging, and (4) the presence of scarring alopecia.39 In addition, telangiectasia and scale are also frequently present.14 33 These changes are more prominent on the centre of the alopecic patch in contrast to other cicatricial alopecias in which clinical activity is more prominent on the peripheral rim (figure 1A).30 Hair on these sites are usually brittle and easily detachable after a hair pull test.27 35 Lesions are more likely to be multiple than solitary, and are confined most commonly on the vertex.33 DLE on the scalp can be itchy, tender or burning, but sometimes they produce no symptoms.14

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Figure 1

(A) Discoid lupus erythematosus. An atrophic porcelain-white plaque on the vertex with areas of erythema, scale, dyspigmentation on the periphery. (B) Dermoscopy of discoid lupus erythematosus. Loss of follicular ostia, areas of follicular plugging, dyspigmentation and pinpoint follicular red dots.

Diagnosis

Dermoscopy has recently been found to approach a specificity of 100% in the diagnosis of DLE when features such as tortuous blood vessels and follicular keratotic plugs are seen (figure 1B).40 Follicular plugging can be a feature of both acute and chronic alopecic lesions.29 Another very specific dermoscopic finding is the presence of follicular red dots, which correspond to multiple widened infundibula bordered by ectatic vessels and extravasated red blood cells.41

The North American Hair Research Society recommends performing at least one 4 mm punch biopsy down to the subcutaneous tissue in the area of active hair loss.36 The HoVert technique obtains both horizontal and vertical sections in a single punch biopsy specimen.42 A horizontal section allows for visualisation of follicular units, whereas a vertical section exhibits the dermoepidermal junction and may be used for immunofluorescence studies.36 Other optional but recommended stains include elastin, mucin or colloidal iron, Gram, and periodic acid-Schiff.34 36 If infection needs to be ruled out, histopathology samples may be sent for cultures.36 The most characteristic histopathological features of DLE are interface dermatitis (basal cell vacuolisation, apoptotic keratinocytes and obscuring of the dermoepidermal junction with inflammatory cells), lymphohistiocytic infiltration around the vessels and appendages, follicular keratotic plugs, mucin deposition, and basement membrane thickening.33 39 Later stages of the disease show reduced follicular units and interstitial fibrosis.30 34

Immunopathology can aid in the correct diagnosis when histopathology does not show the usual distinguishing features of DLE.33 DIF of lesional skin can differentiate DLE from mimickers such as lichen planus or lichen planopilaris, approaching a specificity of 0.97, which is higher than histopathology alone (0.84).43 The lupus band test, described as granular deposition of immunoglobulin and complement deposition at the dermoepidermal junction () , can be positive in as high as 81.7% of patients with scalp DLE.33

ANA positivity among patients with scalp DLE ranges from 15% to 42% of cases.33–35 Hence, it is reasonable to order a complete blood count, urinalysis with urine protein, ANAs and extractable nuclear antigens in a patient with scalp DLE.34 44

Differential diagnoses of DLE (other scarring alopecias)

Frontal fibrosing alopecia

Frontal fibrosing alopecia (FFA) is a special variant of LP presenting as progressive scarring hair loss in a band-like distribution along the frontotemporal scalp mostly affecting postmenopausal women (figure 2).14 51–53 Aside from the recession of the frontal hairline, half of these patients suffer from eyebrow alopecia.34 Other associated clinical features are facial papules, erythematous macules on the glabella and loss of body hair.51 FFA shares the same histological and immunopathological features with LPP, but it additionally involves the intermediate and miniaturised (vellus hair) follicles.34 47 FFA has been reported to coexist with DLE; therefore, the presence of cutaneous lesions of LP or LE elsewhere does not entirely rule out DLE.51 52 Conversely, prior diagnosis of CLE does not preclude the diagnosis of LP scarring alopecia.52

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Figure 2

Frontal fibrosing alopecia. Receding hairline on the frontal scalp, with bilateral loss of eyebrows.

LE-specific alopecia in the setting of acute LE

This type of hair loss in LE may be confused with telogen effluvium, anagen effluvium or alopecia universalis (figure 3).15 62 However, this is considered a distinct entity because it shows interface dermatitis, and obscuring of the dermoepidermal junction by inflammatory cells on histology and a positive lupus band test.18 Some suggest that its clinical presentation more likely fits the non-scarring early stage of DLE, rather than a separate form of LE-specific alopecia.25 In addition, histological findings of early DLE may be similar to those seen in acute and chronic CLE.30 63 However, points which do not support the diagnosis of DLE include (1) a diffuse pattern, (2) absence of follicular plugging and dyschromia on trichoscopy, (3) serology and immunofluorescence tests favouring SLE, and (4) full regrowth of hair after immunosuppressive therapy.19 Establishing the correct diagnosis in this scenario is important in terms of disease classification because the SLICC criteria include both DLE and non-scarring alopecia as clinical items to diagnose SLE, whereas the 1997 American College of Rheumatology criteria only include discoid rash.2 Non-scarring diffuse alopecia in SLE usually reflects the underlying disease activity or severity, with improvement in hair growth once an acute LE flare abates.8 14 16 18 64

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Figure 3

Diffuse hair loss in a patient with acute lupus erythematosus. Alopecia resembles patterned hair loss, but occurs in the setting of a lupus erythematosus flare.

A patchy type of alopecia is also a relatively frequent manifestation in SLE occurring in about 14%–50% of patients.17 24 These multiple partially alopecic patches can occur before, during or after the diagnosis of SLE,24 although it is commonly associated with severe established SLE.15 16 24 Remaining within these patches are fractions of telogen or dystrophic anagen hairs.16 It is believed by some authors that cases previously clinically diagnosed as alopecia areata in the setting of lupus are actually patchy LE hair loss.17 In LE, areas of incomplete hair loss have some degree of erythema within the patch, and dermoscopy may reveal hair shaft hypopigmentation and vessel changes.15 17 Histopathological features that support the diagnosis of LE-specific patchy alopecia are atrophy of the epidermis, hyperkeratosis, interface dermatitis of the epidermal basal cells and pigment incontinence.17 However, in some cases, histopathology alone cannot distinguish LE from AA or even syphilitic alopecia; therefore, further testing such as DIF and serologies should be performed.15 17 24 65 One recommendation is to order an autoantibody panel in patients initially presenting with an AA-like pattern of hair loss to avoid missing the diagnosis of LE.17 In contrast to AA, once the LE disease activity is controlled, hair loss also improves.16

Other forms of lupus-specific alopecia

Although SCLE does not typically involve the head and neck region,63 there have been reports of SCLE affecting the scalp and resulting in patchy hair loss.21 22 These lesions are usually non-scarring, and the morphology can be polycyclic, annular or psoriasiform with thick adherent scale (figure 4).21 22 Histopathology showing psoriasiform hyperplasia with a perivascular mononuclear cell infiltrate can be similar to psoriasis; however, a positive lupus band test favours the diagnosis of SCLE.22 Distinguishing SCLE from early DLE can be challenging.

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Figure 4

Subacute cutaneous lupus erythematosus. Non-scarring, scaly erythematous plaques, with similar papulosquamous lesions on the body (not depicted).

Tumid LE can rarely affect the scalp. The presentation can either be non-inflammatory round patches of hair loss similar to alopecia areata,20 or erythematous reticulated indurated plaques typical of papulonodular mucinosis.23 Biopsy shows no interface change, but displays mucinous infiltration in the deep dermis.20 23 Hair regrowth is possible with antimalarials or intralesional corticosteroids.20 23

Lupus hair

It was Armas-Cruz et al 68 who first described the appearance of dry and fragile short hairs on the frontal hairline of patients with lupus and coined the term ‘lupus hair’ because this sign is so striking that it can suggest the diagnosis of SLE even by just observing a patient from afar (figure 5). The prevalence in a certain cohort of patients with SLE can range from 5% to 30%, and it is found predominantly in women with chronically active SLE.15 24 69 This condition is postulated to be either due to hair shaft breakage68 or to retarded hair growth,15 although a trichogram performed on a few cases showing pointed hairs supports the latter.69 The presence of this type of hair loss in a patient with SLE suggests disease activity or exacerbation,15 68 69 oftentimes improving after the LE flare subsides.14 Growth of fine depigmented hairs can be seen in some patients during the recovery phase.69 There is no formal consensus as to what the clinical definition of ‘lupus hair’ should be. Some consider ‘lupus hair’ to be a variant of telogen effluvium,14 15 whereas others characterise it as vellus hairs on the anterior scalp.24 Moreover, there are no trichoscopic or histopathological features of this clinical sign available in the literature.

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Figure 5

Lupus hair. Fine, brittle hairs on the frontal scalp in a patient with SLE.

Alopecia areata

There is an increased incidence of alopecia areata in LE which reflects their similar autoimmune nature.70 Circular and completely alopecic patches, devoid of erythema or scaling are the characteristic clinical features of AA (figure 6).62 A gentle hair pull test on the edges of the patch reveals dystrophic anagen hairs.66 Dermoscopy classically shows yellow dots, black dots and exclamation point hairs.49 A mononuclear cell infiltrate is typically found surrounding the anagen bulb, although this microscopic finding can also be found in patchy lupus alopecia and syphilitic alopecia.65 If deep dermal mucin deposition is found in addition to the usual biopsy features of alopecia areata, it might be reasonable to search for underlying SLE.71 Cases of tumid LE20 23 and lupus panniculitides72 73 have been reported to be initially diagnosed as AA, pending histopathology. The prognosis of AA is different from the patchy alopecia in LE because AA can have an unpredictable course,62 whereas the patchy hair loss in LE responds favourably to immunosuppressive therapy.17

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Figure 6

Alopecia areata. Non-inflammatory circular patch of hair loss on the parietal scalp.

Ophiasis is more known as a rare form of alopecia areata in which the hairless region follows a band-like distribution along the parieto-temporo-occipital region.17 74 In LE, it can be both scarring or non-scarring.14 Although it is regarded as one of the major features that portend a poor prognosis in AA,62 there are no available data to say this risk is the same as for those with LE.

Telogen effluvium

High fever, anaemia, sudden corticosteroid withdrawal, certain drugs, and physical or mental stress can precipitate this type of hair loss.11 14–16 26 66 Severe metabolic breakdown and increase in certain proinflammatory markers can destructively affect the hair growth cycle.15 The hair follicles then undergo a reactive process manifesting clinically as diffuse hair shedding and/or thinning, often involving both the temporal regions.14 66

Patients often complain of falling hair when they brush or run their fingers through their hair, or when they get up from bed and several strands are left on the pillow.13 Around 150–400 hairs are being shed per day, but it is not until 30% of the scalp is affected that thinning becomes noticeable.14 16 26 A simple hair pull test, which is performed by randomly grasping around 40 hairs, will reveal a count of more than 10% telogen hairs, whereas a hair card placed perpendicularly to the scalp will demonstrate hair regrowth in the recovering disease.26 66 Trichoscopic findings are typically non-diagnostic.49 In a condition known as chronic telogen effluvium, hair loss is abrupt, severe and diffuse, with a fluctuating course lasting for more than 6 months.75

Anagen effluvium

The use of cytotoxic agents (eg, cyclophosphamide) or antimetabolites (eg, methotrexate) in LE and flares in disease activity can cause the rapidly dividing matrical cells of the anagen follicle to temporarily shut down.14 66 74 76 This abrupt arrest in anagen is clinically seen as hair shaft tapering (Pohl-Pinkus constriction), which is prone to intrafollicular breakage.15 74 A hair pull test will reveal several ‘pencil-point hairs’ and telogen hairs.76 Black dots, exclamation mark hairs and monilethrix-like hairs may be appreciated on dermoscopy.49 Timing and onset are critical because anagen effluvium classically occurs as early as 7 days after the triggering event, whereas telogen effluvium ensues months later26 74; there can be an overlap between these two conditions in some patients.74

Differential diagnoses of non-scarring alopecias

Patterned hair loss

The typical location of patterned hair loss (PHL) is on the crown and frontal hairline in men, and on the midline of the crown in women (figure 7).26 A gradual course and a positive family history of PHL can rule in the diagnosis.66 Hair pull test is negative, and characteristically seen on trichoscopy is an increased number of thin, sometimes hypopigmented, vellus hairs admixed with intermediate and thick pigmented hair strands.49 66 However, TE and PHL can coexist, resulting in a more pronounced presentation of alopecia.66 Moreover, PHL is a progressive disease, and therefore difficult to exclude in a patient with lupus with a history of gradually evolving diffuse hair loss (box 2).24

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Figure 7

Patterned hair loss in a female patient. Alopecia resembles a ‘Christmas tree’ configuration on the crown.