The clinical signs of nail psoriasis are described and correlated with the psoriatic involvement of the original nail components responsible for the formation of these signs.
Nail plate abnormalities, ie, pits and grooves, result from previous matrix psoriasis. Nail bed discoloration, onycholysis, and subungual keratosis result from nail bed or hyponychium involvement or both. It is suggested that the yellow greasy-look of psoriatic nails is due to a serum glycoprotein which accumulates in and under the abnormal nail.
Isolation of Candida from subungual debris is frequent. The presence of dermatophytes is rare.
Zaias N. Psoriasis of the NailA Clinical-Pathologic Study. Arch Dermatol. 1969;99(5):567-579. doi:10.1001/archderm.1969.01610230059011