What nail change is commonly associated with psoriasis?

Pitting is indeed the nail change commonly associated with psoriasis. This condition leads to the development of small, pinpoint depressions in the surface of the nails, which can vary in size and depth. These pits are a manifestation of the underlying psoriatic process, where the rapid turnover of skin cells affects the nail matrix and results in this characteristic appearance.

The presence of pitting in nails serves as a clinical clue for healthcare providers, suggesting an underlying diagnosis of psoriasis, especially when it is accompanied by other typical skin findings. The mechanism behind the pitting involves an inflammatory response affecting the nails, correlating with the systemic symptoms of psoriasis.

In contrast, horizontal ridges, also known as Beau's lines, can occur due to a variety of conditions and are not specific to psoriasis. Koilonychia is characterized by spoon-shaped nails and is primarily associated with iron deficiency anemia. Onycholysis refers to the separation of the nail from the nail bed but is more commonly associated with other dermatoses like fungal infections or trauma rather than psoriasis specifically. Thus, pitting stands out as the hallmark nail change linked to this condition.