Psoriatic arthritis (also arthropathic psoriasis or psoriatic arthropathy) is a type of inflammatory arthritis that, accoring to Oxford Handbook of Clinical Medicine, affects around 5-7% of people suffering from the chronic skin condition psoriasis. Psoriatic arthritis is said to be a seronegative spondyloarthropathy and therefore occurs more commonly in patients with tissue type HLA-B27. Treatment of psoriatic arthritis is similar to that of rheumatoid arthritis. More than 80% of patients with psoriatic arthritis will have psoriatic nail lesions characterised by pitting of the nails, or more extremely, loss of the nail itself (onycholysis).