PATHOGENESIS

It has been suggested that FAPD is a variant of LPP10 or a lichenoid scarring variant of AGA.¹¹ The last hypothesis is favored by the variable peri-follicular micro-inflammation observed in histopathology in many cases of AGA.

The cause for the location of a lichenoid infiltrate primarily around miniaturized hair follicles is unknown. Some authors propose that the damaged hair follicles may express different cytokines, initiating a repairing inflammatory process or an apoptosis-mediated organ deletion.^2,6 Others suggest that the lichenoid reaction may be caused by unknown antigenic stimulus on altered AGA hair follicles in immunogenetically susceptible patients.^2,8Androgens may play a role, considering that anti-androgen therapy decreasesscalp inflammation in some cases and stabilizes hair loss progression.^2,9,10

There is one report of familial occurrence of FFA and FAPD in both mother and daughter, suggesting nosological relationship between the two conditions with respect to both the androgenetic background and the inflammatory reaction pattern.^10,13Further studies are necessary to understand the pathophysiology of FAPD.

DIAGNOSIS

FAPD can be diagnosed by combination of physical exam, trichoscopy and histopathology. The main differential diagnoses are AGA, AGA plus seborrheic dermatitis and classic LPP.

Clinically, FAPD presents with patterned hair loss involving androgen dependent scalp - Ludwig pattern in women (Fig. 1) and Hamilton-Norwood pattern in men - with slowly progressive course. Some patients complain of scalp symptoms such as dysesthesia, pain, burning sensation and pruritus.^2,16Physical exam reveals low hair density and sometimes peri-follicular erythema, follicular hyperkeratosis and absence of follicular openings may be detected by open eye.^2,9Rare skin findings are frontal hairline recession similar to FFA, red dots in reticulated pattern on the chest and facial papules.^2,17,18FAPD may affect the eyebrows, but unlike FFA, FAPD is not known to affect eyelashes or other body hair.^17,18Patchy or asymmetric hair loss should be excluded for the diagnosis of FAPD.²

Figure 1  FAPD in a 60-year-old woman, with hair loss on the crown resembling androgenetic alopecia 

Regarding trichoscopy, the most important distinguishing findings between FAPD (Fig. 2) and AGA (Fig. 3) are loss of follicular openings, perifollicular erythema, and perifollicular hyperkeratosis. The last may have a tubular shape around the hair: peripilar casts. When surrounding the emergence of a tuft of 2-3 hairs, they are very typical and represents the optimal biopsy site for histologic diagnosis.^2,6-9Other trichoscopic features are common to AGA, like hair diameter variability and predominance of single hair follicles. The presence of vellus hair in FAPD helps to distinguish it from classic LPP (Fig. 4). In patients with dark skin, a honeycomb pigmented network and scattered white small patches may also be seen, similar in presentation to what is seen in central centrifugal cicatricial alopecia (CCCA).^2,9Dermoscopy alone may not be sufficient to distinguish between CCCA and FAPD in dark-skinned patients.

Figure 2 FAPD Trichoscopy: coexistence of vellus and terminal hair, mild peripilar scaling activity, with peripilar casts surrounding the emergence of tuft of 4 hairs (white arrow), mild interpilar erythema and micro-islands with no follicular orifices (scarring alopecia). 

Figure 3 AGA Trichoscopy: anisotrichia greater than 20%, without peripilar activity. 

Figure 4 Trichoscopy: absence of follicular orifices in a large extension of the field (cicatricial alopecia), mild interpilar erythema and marked peripilar activity, consisting of circumferential desquamation(peripilar casts) and follicular plugs. Note the absence of vellus hair. 

Skin biopsy is important to confirm diagnosis and may be performed with a 4-mm punch biopsy, guided by trichoscopy and processed with horizontal sections. The best locations are peripilar casts. In early lesions, we find a lymphohistiocytic infiltrate surrounding the hair follicle in the isthmus and infundibular regions and follicular interface dermatitis, with vacuolar degeneration of the follicular epitheliocytes.

Interface dermatitis in inter-follicular epidermis is rarely found and lower portions of the follicles, including the hair bulbs, are usually spared. Advanced lesions show concentric peri-follicular lamellar fibrosis (Fig. 5) and fibrosed follicular tracts.^2,6-13,16,17There is hair follicle miniaturization, apoptosis of the basal keratinocytes and a decrease in sebaceous gland number.^2,6 In FAPD, the follicular lichenoid reaction affects both miniaturized and non-miniaturized follicles in the affected scalp.²

Figure 5 FAPD Histopahology: several follicles show perifollicular fibrosis and mild lichenoid infiltrate at the upper follicular level. Note the involvement of a vellus follicle. (horizontal sections, Hematoxylin and eosin, x10). Courtesy of Dr. Maryia Miteva (Miami University). 

Combination of clinical pattern, trichoscopy and histopathology differentiates FAPD from AGA or classic LPP (Table 1).^6,11,14The distinction between FAPD and AGA with seborrheic dermatitis is easy, because in the latter the scales are observed in the inter-pilar spaces and the follicular openings are present. The difference is important, especially in cases in which hair transplantation is being considered, because patients with FAPD, similarly to those with LPP, might not be good candidates for the procedure due to the potential risk of loss of the transplanted hair.²

TREATMENT

There are few available data, limited to small retrospective studies and case reports.

The primary treatment goal is to stabilize the progression of hair loss and a secondary goal is to achieve hair regrowth. However, substantial improvement in advanced disease is impossible. Available agents aim to decrease inflammation and reverse miniaturization. Topical corticosteroids are the mostly used anti-inflammatory drugs, improving scalp symptoms alone and stabilizing hair loss in combination with other agents. Only in one case, stabilization in hair loss with topical clobetasol alone was reported.^19,20Topical 0.05% clobetasol propionate (as foam, solution, and shampoo) has been successfully used combined with 5% minoxidil.¹⁶ Triamcinolone acetonide 0.2% solution used in combination with 5% topical minoxidil has also been a successful maintenance therapy.¹⁷

Oral hydroxychloroquine is commonly used in both FFA and LPP. A few data point its potential benefit in FADP in daily dose of 200-400 mg combined with topical therapy with clobetasol propionate and 5% minoxidil.^2,16,17

Minoxidil is a hair growth promoter, thickening miniaturized hairs and is often used as complementary treatment in scarring alopecias. In FAPD, topical minoxidil is always used in combination with other agents to stabilize hair loss.^1,16,17There are no data about using oral minoxidil in FAPD.

Antiandrogens drugs, even in monotherapy, may stabilize the disease. One man treated with 1 mg daily finasteride presented both decreased inflammation and hair loss.¹

Finasteride seems to be beneficial in women with FAPD refractory to topical therapy with minoxidil and clobetasol.^2,16There are two successful cases of women treated with oral cyproterone acetate combined with topical 5% minoxidil and clobetasol propionate,¹ but recently there is concern about the association between oral cyproterone acetate and the occurrence of meningioma.^19-21

Although topical retinoids may contribute to hair regrowth in patients with AGA, in FAPD no benefit was observed.²

KEY-POINTS

- Fibrosing alopecia in a pattern distribution is a scarring alopecia with lichenoid Inflammation involving miniaturized hair, in androgen-dependent scalp.

- Clues for diagnosis are hair loss resembling androgenetic alopecia and trichoscopic findings of peripilar casts and loss of follicular openings.

- Anti-inflammatory agents in combination with hair growth promoters and/or anti-androgen drugs can stabilize the disease decreasing hair loss.