Diagnosis and treatment of scarring alopecia

Background

Scarring or cicatricial alopecia is a diverse class of conditions of differing etiologies and clinical presentations, in most cases leading to permanent hair loss. These disorders make up approximately 7% of patients evaluated in hair-loss specialty clinics (level of evidence: 5). Scarring alopecia can be primary, characterized by inflammation and destruction of the pilosebaceous unit with eventual replacement of subcutaneous tissue with fibrous tracts, or secondary as a result of trauma, cancer, radiation, or thermal burns (level of evidence: 5). ^, Primary cicatricial processes can be further classified into neutrophilic, lymphocytic, or mixed by the predominant inflammatory cell type seen on histology during the active phase of disease ( Table 3.1 ) (level of evidence: 5).

Unlike nonscarring alopecia where the follicular unit is preserved and treatment is centered on hair regrowth, treatment for scarring alopecia is largely aimed at reducing inflammation and preventing disease progression. Consequently, hair loss can be disfiguring and may contribute to increased psychosocial burden and decreased dermatology life quality index (DLQI) scores in patients with scarring alopecia compared with those with nonscarring alopecia (level of evidence: 1b). Early diagnosis and initiation of treatment is essential for a better prognosis in these patients.

Structural and functional differences in scarring alopecia

The pilosebaceous unit consists of three anatomic structures: hair follicle, sebaceous gland, and arrector pili muscle (level of evidence: 5). The hair follicle, an epithelial organ, can further be divided into three regions: the infundibulum (uppermost segment) extending from the insertion point of the sebaceous gland to the follicular orifice; the isthmus (middle segment) extending from the entrance of the arrector pili muscle to the insertion of the sebaceous gland; and the bulb (lowermost segment) extending from the base of the hair follicle to the arrector pili muscle. Near the attachment site of the arrector pili muscle and opening of the sebaceous gland there is an area on the outer root sheath of the hair follicle called the bulge region where multipotent stem cells are located (level of evidence: 3a). ^, During the hair cycle, quiescent follicular stem cells are transiently activated in the early anagen (growth) phase (level of evidence: 5). These cells can proliferate and further differentiate to support elongation or regeneration of the hair shaft.

In nonscarring processes, while the histopathology is largely disease dependent, all conditions share the finding of an intact and healthy hair bulge region in early stages of disease, allowing the hair follicle to regenerate with sufficient treatment. Contrarily, scarring alopecia involves destructive inflammation around the infundibular, and variably isthmic, region of the hair follicle. This causes damage to the follicular bulge region and leads to the loss of epithelial stem cells necessary to regenerate the hair follicle (level of evidence: 2b). ^, With persistent inflammation, the involved tissue becomes fibrotic, resulting in permanent hair loss. The fundamental differences between scarring and nonscarring alopecia are summarized in Table 3.2 .

Evaluation of scarring alopecia

Onset of scarring alopecia occurs most commonly in middle-aged adults, with only rare exceptions of familial genodermatoses developing during childhood and adolescent years (level of evidence: 5). ^, This may be an important distinguishing clue from some nonscarring alopecias such as alopecia areata (AA), which can affect individuals at any age (level of evidence: 2a). The threshold for a punch biopsy in patients presenting with clinical signs and symptoms concerning for a cicatricial process should remain low, as pathology examination allows for a more definitive identification of inflammatory infiltrates ( Pearl 3.1 ) . Often, two areas of the scalp are biopsied, both taken from the edge of an area of active inflammation to identify predominant cell types and provide possible insight on the underlying pathology (level of evidence: 5). However, biopsy alone may be insufficient for making an accurate diagnosis (level of evidence: 1b). A thorough patient history and clinical examination are key to establishing onset, disease course, family history, medication history, associated symptoms, and hairstyling and haircare practices. Extrascapular areas of hair growth such as the eyebrows, eyelashes, axillae, extremities, and genitalia should also be assessed, in order to establish the extent of disease involvement.

On clinical examination, there are several features that may be present to allow distinction between a cicatricial and noncicatricial process. Evidence of smooth, fibrotic alopecic patches on the scalp, follicular prominence, loss of follicular ostia, perifollicular erythema or hyperkeratosis, papules, and pustules in affected areas of the scalp are several signs that may point to a scarring process (level of evidence: 5). In addition, some scarring alopecias have characteristic findings such as skin atrophy in lichen planopilaris (LPP) (level of evidence: 5) and dyspigmentation in cutaneous lupus erythematosus (level of evidence: 5).

This chapter will focus primarily on the most common cicatricial processes encountered by dermatologists and therefore the most important to understand: LPP, frontal fibrosing alopecia (FFA), and central centrifugal cicatricial alopecia (CCCA) ( Table 3.3 ).