Lichen amyloidosus as a sweat gland/duct-related disorder: resolution associated with restoration of sweating disturbance.

BACKGROUND: Although a number of pathological processes resulting in amyloid deposition have been described in lichen amyloidosus (LA), no attention has been paid to the involvement of sweat glands/ducts in the pathogenesis of LA. According to recent studies, follicular structures are usually spared in serial histological sections of LA, and deposits of amyloid are likely to be confined to areas that display xerosis, suggesting that decreases in skin wetness by sweating disturbance seem to initiate LA. OBJECTIVES: To investigate whether sweating disturbance could represent an early event that triggers LA, and whether resolution of LA could be induced by restoring the sweating disturbance. METHODS: By using the impression mould technique, which allows an accurate quantification of individual sweat glands/ducts actively delivering sweat, we examined sweat responses to thermal stimulus in LA lesions before and after treatment with a moisturizer. RESULTS: Sweating disturbance was most profoundly detected in the 'hub' structure of the LA papule, and this disturbance due to leakage of sweat could be restored by short-term treatment with a moisturizer, particularly when used under occlusion. CONCLUSIONS: This study was limited by the relatively small sample size. Treatment of LA should be primarily directed at preventing leakage of sweat into the dermis or epidermis and therefore sweat delivery to the skin surface could be made easier.