Pitting of the nails, typically the fingernails, is characterized by depressions in the surface of the nail. Nail pitting is caused by defective development of the layers of the superficial nail plate. It is common in patients with psoriasis and can affect up to 50% of people suffering from this condition. Nail pitting can also be associated with other conditions, including connective tissue disorders, alopecia areata, and sarcoidosis. Any condition that can cause a superficial and localized inflammation of the skin (dermatitis) can also affect the nails and result in nail pitting. Nail pitting can be associated with other abnormalities of the nails, including nail separation, flaking or crumbling, or other damage to or changes in the nail. Nail pitting that is associated with disease processes generally shows involvement of multiple or all nails, while trauma to an individual nail bed can cause localized pitting or disruptions in a single nail.