Nail Signs Koilonychia (spoon nails) 反甲

Koilonychia (spoon nails)
The nail plate is thinned and flattened with upward eversion of its lateral and distal edges, leading to a concave spoon-like shape. Koilonychia is common in infancy as a benign feature of the great toenail, although insome infants its persistence may be associated with a deficiency of cysteine‐rich keratin in trichothiodystrophy. The most common systemic association is with iron deficiency and haemochromatosis, although the majority of adults with koilonychia demonstrate a familial pattern, which may be autosomal dominant. In adults, koilonychia is rare and occurs in association with severe iron deficiency and systemic amyloidosis. It can also be seen in manual laborers who have contact with irritants and detergents that damage the nail plate. In dermatoses such as psoriasis and dermatophyte infection, nail bed hyperkeratosis may push the nail up distally to produce a spoon‐shaped nail.

Koilonychia

反甲，指甲板变薄并变平，其横向和远端边缘向上外翻，导致呈勺状凹陷形状。 幼儿（1-4岁）的大脚趾甲常见，是生理性的，最终自发消退。在一些幼儿中，其持久不退可能与营养不良，含半胱氨酸的角蛋白缺乏有关。 尽管大多数有反甲的成年人表现出家族性模式，可能是常染色体显性遗传，但是，反甲也可能与严重的铁缺乏症和全身性淀粉样变性相关。 在体力劳动者中也可以看到与刺激物和清洁剂接触会损坏指甲板的情况。牛皮癣和皮肤癣菌感染的皮肤病中，甲床过度角化可以将指甲向远侧推动以产生勺状指甲。

Reference:

 

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  7. Alanko K, Kanerva L, Estlander T, et al. Hairdresser’s koilonychia. Am J Contact Dermatitis 1997;8:177–8