Cohen Philip R
Department of Dermatology, University of California San Diego, La Jolla, California, USA.
Skin Appendage Disord. 2018 Oct;4(4):331-334. doi: 10.1159/000487860. Epub 2018 Mar 26.
Half-and-half nails were originally described as a transverse leukonychia in patients with chronic renal disease; other conditions (such as Behcet's and Crohn's disease) and medications (such as isoniazid) have also been associated with the nail changes. However, longitudinal half-and-half nails (affecting the medial aspects of the nails) have previously been reported on the great toes of an older woman and, in the present case, on the thumbs of an elderly man; neither person had Behcet's, Crohn's, or kidney disease or was receiving isoniazid. The woman had a true leukonychia, bilateral hallux valgus deformity, and chronic trauma to her medial nail folds. The man had a nontraumatic apparent leukonychia and bilateral koilonychia; the non-white lateral area of his left thumb also had a linear groove (resulting from a digital mucous cyst on the proximal nail fold) and subun gual hyperkeratosis. In conclusion, longitudinal half-and-half nails are a rare phenomenon that has not been associated with either a systemic disease or medication; the acquired nail change can present either as an idiopathic finding or occur secondary to chronic trauma.
对半甲最初被描述为慢性肾病患者的横向白甲；其他病症（如白塞病和克罗恩病）及药物（如异烟肼）也与指甲改变有关。然而，纵向对半甲（累及指甲内侧）此前曾在一名老年女性的大脚趾上有过报道，在本病例中，则出现在一名老年男性的拇指上；两人均无白塞病、克罗恩病或肾病，也未服用异烟肼。该女性有真性白甲、双侧拇外翻畸形以及内侧甲襞的慢性创伤。该男性有非创伤性明显白甲和双侧匙状甲；其左手拇指的非白色外侧区域还有一条线性沟（由近端甲襞上的指黏液囊肿所致）和甲下角化过度。总之，纵向对半甲是一种罕见现象，与全身性疾病或药物均无关联；这种后天性指甲改变既可以是特发性表现，也可以继发于慢性创伤。
