Surface pitting is the best-known sign of psoriatic nail disease. Pits may be random but are often linear.

Onycholysis. Separation of the distal nail plate may be misdiagnosed as a Candida or fungal infection.

Oil spot lesions. Brown-red spots represent accumulation of serum under the nail.

Matrix lesions. Distortion of the entire nail plate occurs when psoriasis involves the nail matrix. The entire nail plate is affected.