Cicatricial alopecia: classification and histopathology

Primary cicatricial alopecias are a diagnostically challenging group of disorders characterized by folliculocentric inflammation resulting in destruction of hair follicles and irreversible hair loss. They are classified according to a consensus-issued classification scheme based on the predominant cell type present: lymphocytic, neutrophilic, or mixed. Histopathology is a pivotal component of the diagnostic evaluation. Early diagnosis is critical since timely institution of treatment can halt progression of permanent hair loss. Salient histopathologic findings are presented in this review, along with adjunctive clues derived from interpretation of special stains and direct immunofluorescence studies. Despite careful evaluation, accurate diagnosis may remain elusive in some instances. The primary cicatricial alopecias often share overlapping features. The highest diagnostic yield is procured when histology is correlated with the clinical presentation.