Scarring alopecia

Scarring or cicatricial alopecias are characterized by irreversible hair loss, resulting in profound psychosocial impact on those affected. Clinically, they are manifested by white, fibrosing patches, with absent follicular openings, often associated with varying degrees of perifollicular inflammation. On histopathology, inflammatory infiltration of the upper portion of the hair follicle is evident, resulting in its irreversible destruction and replacement by fibrous scar tissue.

This umbrella term encompasses a spectrum of disorders, broadly categorized as primary or secondary cicatricial alopecias. This classification depends on whether scarring alopecia results from a primary inflammatory or autoimmune process, or it is caused by physical, mechanical, traumatic factors and neoplastic or scarring skin diseases, respectively. Primary scarring alopecias are further classified into lymphocytic, neutrophilic and mixed, depending on the predominating cell type in the inflammatory infiltrate.

Diagnosis of scarring alopecia poses many difficulties, and is based on history, clinical and dermoscopic examination, and histopathology, the latter considered as the diagnostic gold standard. However, skin biopsy is an invasive procedure that has several limitations. The introduction of trichoscopy has revolutionized the diagnostic landscape, providing a non-invasive and highly accurate alternative. By bridging clinical and histological findings, trichoscopy has become a cornerstone in alopecia diagnosis, reducing the necessity for biopsies and optimizing patient care. Numerous trichoscopic clues have been described and integrated into diagnostic algorithms, most notably the 3-step diagnostic algorithm, which effectively applies pattern analysis in trichoscopy.

Treatment is challenging, and often proves unrewarding. Advances in understanding the pathophysiology, as well as the contributing and associated etiologic factors, have led in the introduction of innovative approaches for scarring alopecia. Furthermore, novel therapeutic agents, such as JAK inhibitors and biologics, offer promises for a more effective management, not only in alopecia areata, but also in primary cicatricial alopecia. Nevertheless, prevention and early diagnosis, before irreversible hair loss is established, remains of outermost importance, as well as rescue therapies for rapidly advancing scarring alopecia.