Psoriasis is a skin condition that causes red, flaky, crusty patches of skin covered with silvery scales. These patches normally appear on your elbows, knees, scalp and lower back, but can appear anywhere on your body.
Between 5-20% of patients with psoriasis may develop an associated arthritis (inflamed joint). The lining of the joint, called the synovium, becomes inflamed and swollen. With chronic inflammation, the joints become deformed and unstable. The joint surface wears out with further erosion. Apart from the hands, this arthritis can affect joints in the spine, feet, and jaw.
Psoriatic nail disease occurs in about 50% of patients with psoriasis and is more common in patients who suffer with psoriatic arthritis. Nail psoriasis occasionally occurs in the absence of any skin psoriasis. Characteristic nail changes include pitting (small depressions measuring less than 1 mm in diameter), discolouration (circular areas resembling an oil drop), subungual hyperkeratosis, crumbling of the nail plate, and onycholysis (separation of the nail plate from the nail bed).