BACKGROUND
Frontal fibrosing alopecia (FFA) is a primary lymphocytic cicatricial alopecia, considered a variant of lichen planopilaris due to histological similarities.1 Clinically, FFA causes gradual hair loss of the frontotemporal hairline and is commonly associated with loss of eyebrows and body hair. FFA may occur in conjunction with lichen planus pigmentosus (LPPigm), another lichenoid condition (Figure 1). LPPigm is a macular variant of lichen planus that presents as diffuse or reticulated grey to brown macules on sun-exposed areas and in flexures, eventually evolving into large hyperpigmented patches.2 LPPigm mainly affects the face and neck but can sometimes progress to the trunk and upper limbs and may be associated with a burning sensation or itch.3 There is limited data regarding the association between these two conditions, though various reports have documented a link.4-8
Epidemiology
Concomitant FFA and LPPigm most commonly affect dark-skinned individuals, with one case series describing its occurrence in 5 women with skin phototypes II and III.9 The first study associating both conditions evaluated 24 patients from South Africa, with 91% of patients identifying as African.4 Subsequent reports similarly noted its association in dark skinned patients.6,7,10 More recently, a multicenter retrospective descriptive analytical study involving 104 patients with combined FFA and LPPigm found that most affected patients had skin phototypes IV, V, and VI (74.1%).5 Data regarding whether LPPigm precedes FFA is conflicting. In the patient cohorts evaluated by Dlova et al and Romiti et al, LPPigm preceded FFA in all patients, with an average lag time of 14 and 10 months respectively between each diagnosis.4,7 These case series consisted of smaller cohorts, involving 24 and 16 patients respectively. The observed trend was less pronounced in the larger, multicenter study, with LPPigm preceding FFA in 56.8% of cases5 and 51% of cases in another case series of 37 patients.6 Though there is inconsistent evidence elucidating the temporal relationship between LPPigm and FFA, LPPigm appears to precede FFA in some patients, and is thus a proposed risk factor for FFA.4 Most studies have reported a larger frequency of concomitant FFA and LPPigm in post-menopausal women,5-7 which is consistent with the general FFA epidemiology.5 In Dlova et al’s study, most patients were premenopausal. Increased mechanical trauma associated with hair grooming styles is a potential explanation for the relatively early manifestation of FFA in African patients.4
Pathophysiology
A continual inflammatory response and breakdown of immune privilege of the epithelial hair follicle stem cells is pivotal in the pathogenesis of FFA. CD8+ T-lymphocytes and IFN-gamma are key mediators of the associated inflammatory processes.11,12 The pathogenesis of LPPigm remains unclear, though it is known that CD8+ T-lymphocytes and mediators such as interferon-gamma, tumor necrosis factor-alpha, interleukin 6, and lymphocyte function-associated antigen 1 play a role.11,3 The clinical parallelism and progression between LPPigm and FFA, and their histological associations suggest that LPPigm and FFA represent distinct stages within the spectrum of the same underlying disease,4 though more research is necessary to evaluate the association.
Treatment
FFA is a chronic condition, requiring long-term treatment, often with a combination of therapies. Commonly prescribed topical
