Alopecia is defined as the partial or complete loss of hair in areas where hair is normally expected to grow.1 Hair loss has a significant impact on psychosocial function and can provoke anxiety and distress that may be disproportionate to its apparent objective severity.2,3

Lichen Planopilaris (LPP) is the most common primary scarring alopecias.4,5 Three clinical subtypes have been described: the classic subtype, Frontal Fibrosing Alopecia (FFA) and the Graham-Little-Piccardi-Lassueur syndrome.6–8 The etiopathogenesis of LPP is not fully understood. However, it is believed that an immune privilege collapse, induced by interferon-gamma, occurs in the follicular bulge of patients with LPP.9 This phenomenon allows for differentiation between lesional and non-lesional scalp in affected individuals.9 Due to the permanent nature of the condition, early management is essential.

Multiple medical therapies have been described, with varying degrees of efficacy. The main goals of treatment are to alleviate symptoms, reduce disease progression, and improve hair density.10–12 Surgical hair restoration has emerged as a cosmetic alternative. Surgical approaches include excision of alopecic scalp areas, scalp flaps, and hair transplantation.13

Hair transplantation aims to cover areas of scarring alopecia. The procedure involves relocating hair follicles from unaffected areas to recipient sites, with the expectation that transplanted follicles will continue producing healthy terminal hairs.14 Techniques for harvesting donor follicles include strip harvesting (follicular unit transplantation – FUT) and follicular unit extraction (FUE).15 The choice of technique typically depends on the clinical characteristics of the alopecia, the patient’s specific needs, and the surgical expertise of the treating team.

Hair transplantation in scarring alopecia presents unique challenges. Scarring alopecias alter the anatomy of the recipient site and may also affect potential donor areas. Other factors to consider include the potential for disease reactivation, donor site availability, scalp laxity, individual healing patterns, vascularization of both donor and recipient regions, and the location of the resulting scar.16

There are a few reports of patients with primary scarring alopecias undergoing hair transplantation. The use of this technique remains controversial due to the high likelihood of poor follicular growth post-transplant.17,18 Furthermore, cases of LPP developing after hair transplantation have been reported.18 The most recent systematic reviews addressing the topic of the present study were published in 2019 and 2021.19,20 However, the first one included other types of primary scarring alopecia,19 and neither review considered the four most recent studies reporting this procedure, which contributed a substantial number of new cases. Consequently, the objective of this study is to review the current evidence regarding the efficacy of hair transplantation in patients with LPP.

LPP is the most common type of scarring alopecia and has a significant impact on quality of life.38 Early diagnosis and prompt treatment are essential to halt disease activity. However, its management remains challenging, as responses to conventional therapies are often incomplete or absent.6 As a result, disease progression may lead to the development of scarring alopecic plaques.

Hair transplantation in LPP is controversial, mainly due to the risk of poor follicular growth and consequent graft failure. Additional concerns include determining the optimal timing of the procedure, the most suitable method for follicular unit extraction, and the potential need for continued active treatment for LPP following transplantation.

In this review, the authors found that graft survival was generally high (survival rate > 80%) during the first year in most patients. Between the first and second year, hair growth rates remained above 70%. A recent meta-analysis reported high graft survival rates in non-scarring alopecia (84.9%), with a mean follow-up of 1.2-years post-surgery, and in secondary scarring alopecia (88.6%), with a mean follow-up of 11.2-months, using only micrografts.39 Thus, in the short and medium term, graft survival in LPP appears comparable or only slightly lower than in both non-scarring and secondary scarring alopecia.

However, in the present review, after the second year, the survival rate declined to ≤ 41% in the majority of patients (89%), despite initially favorable growth. In one study, a biopsy of a residual follicular unit revealed histopathological findings consistent with FFA.29 This may suggest that the recipient site had ongoing subclinical inflammatory activity, despite apparent clinical stability, that LPP-related inflammation was predominant in the recipient area, or that the donor follicles may have been affected by subclinical LPP despite the absence of clinical or trichoscopic signs.29,35

In the present review, ten studies reported clinical inactivity at the time of transplantation. LPP is considered an “unstable” scarring alopecia due to its tendency to progress and relapse intermittently over time.40 Defining stability in LPP ‒ whether in the classic subtype or FFA ‒ is inherently complex. The Lichen Planopilaris Activity Index has been proposed as a tool to assess disease activity and progression.41 However, it is not a standardized tool, and in fact, only one study in our review used it.36

Thus, no sensitive biomarker has yet been identified to determine disease remission.35 Consequently, the assessment of stability largely relies on the clinician’s judgment. Moreover, despite an apparently inactive state, the microtrauma induced during hair transplantation may reactivate the disease or even trigger de novo development of LPP.21,42 Additionally, follicular inflammation has been reported in areas affected by FFA, although not in the transplanted follicles.33

The included studies reported variable durations of clinical stability prior to transplantation, ranging from zero to up to five years.25,34 Notably, one study described a case in which hair transplantation was performed following the failure of conventional therapies in a patient with FFA.28 By contrast, the clinically recommended quiescent period prior to hair transplantation is typically one to two years without ongoing therapy.40,43 However, there is no robust statistical evidence supporting this timeframe. The absence of individual patient data regarding clinical inactivity in LPP limits the ability to draw reproducible conclusions on its impact on hair graft survival rates.

The authors found a similar proportion of patients who had FUE and FUT techniques for follicular unit harvesting. However, all patients who underwent the strip technique presented with FFA. In contrast, the classic subtype was the most common presentation (70%) among those who underwent FUE. This may be related to the availability of donor follicle areas due to the different involvement patterns of LPP subtypes. Moreover, the possibility of performing FUE to harvest follicular units from the beard or anterior trunk allows for consideration of alternative donor sites.31,44

In addition to the unstable course of LPP, the potential concomitant development of androgenetic alopecia (AGA) ‒ characterized by progressive hair thinning following a defined pattern ‒ must also be taken into account.40 This consideration is essential in transplantation planning in order to avoid “islands” of transplanted hair within a “sea” of hair affected by AGA.40 Hair transplantation does not halt the progression of AGA; therefore, long-term medical therapy to slow the process is essential.45

In parallel, maintenance medical treatment in patients with LPP after hair transplantation is not standardized. In our review, five studies explicitly reported the continuation of treatment following transplantation.27,28,33,34,37 These studies described the use of 5-alpha reductase inhibitors,27,28,37 topical corticosteroids,27,28 topical minoxidil,28,37 and topical calcineurin inhibitors,33 with variable durations. Vañó-Galván S. et al. commented that patients received medical therapy for FFA after transplantation, but the authors did not specify the treatment regimens or their duration.34 Consequently, there is no significant evidence regarding the use of maintenance anti-inflammatory therapy, nor whether such treatment should be initiated only upon detection of clinical activity. Nonetheless, the use of 5-alpha reductase inhibitors may be considered as a strategy to slow AGA progression, while potentially stabilizing inflammation, particularly in patients with FFA.46,47

A study proposed the use of a transplantation test with 400–500 follicular units in patients with AFF with active inflammation and fibrosis.48 The authors suggested that, after monitoring graft survival over a period of two to five years, a standard transplantation could be considered.48 In our review, six studies reported performing a transplantation test.25,27,29–31,36 Although the reasons for not proceeding to subsequent transplantation were not always explicit, these may have included loss to follow-up with marked shedding of transplanted hair upon reassessment,27 follicle loss after 18-months to two years post-transplantation,29 or study design limitations.36

In three studies, after achieving an initially satisfactory outcome, hair transplantation was performed. Podda M et al. carried out a preliminary test with 50 follicular units.25 After four months, they performed between two and five additional sessions with 200 grafts, reporting acceptable graft survival.25 Greco C. et al. conducted a trial in 1 × 1 cm areas within the alopecic region.30 After confirming hair growth at four months, the authors proposed extending the transplantation to all affected alopecic areas.30 Similarly, Saxena K. et al. performed a test with 50-units and, after achieving an 80% growth rate at 10-months, completed the transplantation.31 Since graft survival progressively declines, particularly after the second year, defining the “success” of a transplantation trial is challenging without long-term follow-up.

This study had several limitations. First, despite the extensive search across multiple databases, there was a risk of missing potential articles indexed in alternative databases or published in languages other than English or Spanish. Moreover, the available studies on hair transplantation in patients with LPP were case reports or case series, and no prospective studies or clinical trials were identified. Even more, there was a marked heterogeneity among the included studies: some authors omitted relevant clinical information about patients and treatments, graft survival rates were not measured in a standardized manner, and follow-up times were inconsistent. Given that the primary goal of hair transplantation is cosmetic in nature, reporting bias cannot be excluded. Furthermore, because graft survival declines over time, long-term patient follow-up is essential. Future studies should therefore include larger cohorts, with homogeneous treatment protocols and follow-up regimens, to provide more robust conclusions.

In this study, the authors investigated the application of hair transplantation in patients with LPP. The authors conducted a systematic review with the aim of identifying the clinical characteristics of patients and the efficacy of hair transplantation. The studies retrieved were case reports or case series. With the exception of one study, hair transplantation was performed in patients without clinical activity; however, the duration of inactivity varied widely, ranging from zero to 60-months.

The technique for follicular unit extraction varied, with a similar proportion of FUE and FUT, although the distribution of clinical phenotypes differed. A progressive decline in graft survival rate was observed. While survival rates were above 70% up to the second year, a clear decline was noted thereafter, with survival rates of 41% or lower.

Although hair transplantation may be considered a cosmetic option in patients with LPP, the data from the available studies are heterogeneous. Further research is needed to better define graft survival rates and to identify interventions that may improve outcomes. Prospective studies with larger patient cohorts and standardized treatment and follow-up protocols are required to generate more robust evidence.

Rodolfo David Palacios_Diaz: 0000-0002-8353-7481

Miguel Antonio Lasheras-Pérez: 0000-0001-7429-9592

The entire dataset supporting the results of this study was published in this article.

None declared.

Rodolfo David Palacios-Diaz: The study concept and design; data collection, or analysis and interpretation of data; statistical analysis; writing of the manuscript or critical review of important intellectual content; data collection, analysis and interpretation; approval of the final version of the manuscript.

Miguel Antonio Lasheras-Pérez: The study concept and design; data collection, or analysis and interpretation of data; effective participation in the research guidance; critical review of the literature; approval of the final version of the manuscript.

None declared.