Cicatricial alopecia: clinico-pathological findings and treatment.

Cicatricial alopecia is the result of various diseases of the scalp. It is usually circumscribed but may be widespread. It presents as areas of hair loss in which the underlying scalp is scarred, sclerosed, or atrophic. In early stages, the underlying disease is usually diagnosable clinically and histologically, but in late stages, only scarring may be evident. The scarring is the result of the destruction and fibrosis of hair follicles. A recent hypothesis suggests that the primary pathology of many of the mechanistically obscure scarring alopecias occurs in the sebaceous gland. It is speculated that inadequate sebaceous gland function could lead to hair follicle destruction.1 The failure of affected follicles to regrow is thought to be because of destructive changes at the level of the insertion of the arrector pili muscle into the region of the follicular bulge.2 This is where the slow cycling hair follicle stem cells that are capable of initiating follicular renewal at the end of the resting phase of the hair cycle are located.3 Not all disorders classified under the term cicatricial or scarring alopecia have histological evidence of true scar formation in which elastic fibers are destroyed.4,5 For example, true scars differ from scleroderma, in which collagen fibers are thickened and hyalinized but connective tissue is not destroyed. Under the term “cicatricial alopecia” are included diseases in which there is true scarring because of the destruction of the hair follicle and others in which there is no true scar formation. The latter could better be called “permanent alopecia.” The hallmark of permanent alopecia is middermal hyalinization involving the follicular bulge. Follicular destruction in scarring alopecia may be primary or secondary.6,7 In primary scarring alopecia, the hair follicle itself is the principle target for destruction, with relative sparing of the intervening dermis. Causes of primary scarring alopecia include discoid lupus erythematosus, lichen planopilaris, pseudopelade, and folliculitis decalvans, and are listed in Table 1.7 Secondary scarring alopecia results from nonfollicular events that impinge upon and eventually destroy the follicle. The permanent follicular scarring is the result of the close proximity of the follicles to the primary pathological process. The scarring may be secondary to numerous congenital or nevoid disorders affecting the hair follicle such as nevus sebaceus.8 Destruction of hair follicles may also result from physical and chemical trauma or pathological changes in the dermis because of sclerosing diseases or granulomatous or neoplastic infiltrates. Causes of secondary scarring alopecia are shown in Table 2. Primary scarring alopecias are reviewed here. In many cases, extensive permanent damage is already present when patients are first seen, leaving little hope for regrowth with specific treatment; however, it should be possible to recognize and diagnose cases of scarring alopecia at an earlier stage in order to obtain better treatment outcomes. To gain further clinico-pathological data about cicatricial alopecia, 358 consecutive patients were studied, and horizontal and vertical sections of scalp biopsies were examined. Primary and secondary scarring alopecias were seen and salient details are given here.