Acquired hair fragility in pili anulati: Causal relationship with androgenetic alopecia

Pili anulati are defined by characteristic alternating light and dark bandi ng in the hair shaft, due to air-filled spaces between the macrofibrillar u nits of the hair cortex, and are regarded as a congenital hair shaft disord er without increased hair fragility. Two cases of pili anulati are presente d, in which fragility of hair developed in a causal relationship with the o nset of androgenetic alopecia. Accordingly, trichorrhexis-nodosa-like hair fracturing was exclusively limited to the androgenetic region. In general, secondary trichorrhexis nodosa is an unspecific finding related to excess s tress of hair in relation to its fragility. With onset of hair thinning due to androgenetic alopecia, progressive reduction of hair shaft diameter may cause increased fragility in pili anulati. In this case, hair shaft fractu ring occurs within the area of androgenetic alopecia and colocalizes with t he air-filled cavities of pili anulati. Copyright (C) 2001 S. Karger AG, Ba sel.