Hur K, Han B, Lim SS, et al. - Since trachyonychia, a rare inflammatory disease of the nail matrix, has a more chronic course in adults than in children, but the histopathologic characteristics of the disease have not been adequately documented in the literature, researchers retrospectively reviewed the pathologic characteristics of idiopathic trachyonychia in adult cases at the center. In total, 30 cases were involved. The median age was 55.5 years and the median disease duration was 84 months. Upper dermal lymphocytic infiltrates (93.3%), acanthosis (86.7%), exocytosis (63.3%), spongiosis (63.3%), parakeratosis (46.7%), psoriasiform hyperplasia (40%), eosinophilic infiltrates (33.3%), vacuolar degeneration (33.3%), lichenoid pattern (13.3%), Civatte body (6.7%), and collection of neutrophils in the stratum corneum (3.3%) were observed by histopathological analysis. The majority of cases showed inflammatory cell infiltration with epidermal changes. Active therapy with anti-inflammatory agents should be considered, in view of the inflammation and chronic course of idiopathic trachyonychia in adulthood. Additionally, during the initial examination, mycological tests should be considered as there are cases of fungal co-infection.