AbstractBackground  Lichen planopilaris (LPP) is an inflammatory disease that affects the scalp and tends to produce cicatricial alopecia. The inflammatory process frequently results in the disruption of the basal cell of the external root sheath of the hair follicle.Objectives  To investigate the alterations in the basement membrane zone (BMZ) in LPP by immunohistochemistry.Methods  Skin biopsies from six patients with LPP plus six normal controls were studied by immunohistochemistry with antibodies to the following BMZ components: cytokeratin 5, cytokeratin 14, BP230 (bullous pemphigoid), BP180, plectin, laminin 5, collagen IV and collagen VII.Results  The localization and staining of the hemidesmosome, laminin and collagen components were strikingly different in the inflamed follicular epithelium when compared to the uninvolved follicles or interfollicular epithelium in active LPP lesions. The hemidesmosome‐associated complexes were weakly expressed and discontinuous in involved hair follicles. The expression of laminin‐5, type IV collagen and type VII collagen was disrupted and not linear along the BMZ with finger‐like projections of the staining protruding into the dermis. The expression of the intermediate filaments was normal.Conclusion  These alterations in the BMZ in LPP may explain the abnormal healing at follicular level which leads to irreversible hair loss and scarring in this condition.