Distal onycholysis: Distal onycholysis can occur on the one hand by oil stain formation in the nail bed, when the oil stain, by area growth finds connection to the hyponychial air-containing space. Thus, air enters under the nail, causing whitening of the nail(onycholysis semilunaris).
Distal onycholysis can also result from psoriatic involvement of the hyponychium. This results in distal detachment of the nail plate from its epithelial support, fraying the originally sharply drawn line of adhesion between the distal nail matrix and the skin.