Although researchers are still uncovering the exact processes that occur in the body in psoriasis, experts believe that this chronic inflammatory disease occurs as a combination of genetic susceptibility, environmental factors, and a dysfunction in the immune system. These processes result in the plaques on the skin and can also affect the nails.1
Abnormal activation of the immune response
In a healthy immune system, foreign substances are recognized by the antigens on the surface of their cells. One of the white blood cell types is the T-cell lymphocyte. T lymphocytes, or T-cells, attack the antigens directly and help control the immune response. They also release chemicals called cytokines that govern the entire immune response.2
In people with psoriasis, the immune system is abnormally activated following an environmental trigger, like physical stress, trauma or infection. The immune system begins attacking healthy tissue and creating chronic inflammation.
Certain infections have been shown to be involved in the exacerbation and continuation of psoriasis. One of the fungal infections that seems to activate skin and nail psoriasis is Candida albicans. The T-helper cells Th17 and Th22 are activated in the presence of Candida, and they produce interleukin(IL)-22 and IL-17A/F. (Interleukins are a type of cytokine). IL-22 and IL-17A/F stimulate keratinocytes, the cells which are found in the epidermis (the outermost layer of the skin). Candida stimulates the production of cytokines and seems to act as a trigger for nail psoriasis.1
Tumor necrosis factor
Tumor necrosis factor-alpha (TNF-alpha) is another cytokine that is found in abnormally high levels in people with skin and nail psoriasis.1 TNF-alpha has multiple functions, including increasing inflammation and inducing necrosis (death) of tumor cells.
Symptoms of nail psoriasis
When psoriasis affects the nails, it can cause changes to the nail matrix (where the new nail is formed), the nail bed (the skin underneath the nail), or the nail plate (what we commonly call the fingernail or toenail). Nail psoriasis can present as:
In addition, vitamin D has been found to defend against infection and support a healthy skin barrier. Studies have shown that vitamin D can be helpful in treating nail psoriasis.1
Ventura A, Mazzeo M, Gaziano R, Galluzzo M, Bianchi L, Campione E. New insight into the pathogenesis of nail psoriasis and overview of treatment strategies. Drug Design, Development and Therapy. 2017;11:2527-2535. doi:10.2147/DDDT.S136986.
Immune response. Medline Plus, U.S. National Library of Medicine. Accessed online on 9/29/17 at https://www.nlm.nih.gov/medlineplus/ency/article/000821.htm
Pasch MC. Nail psoriasis: a review of treatment options. Drugs. 2016 Apr 4. [Epub ahead of print] Accessed online on 4/13/16 at http://dx.doi.org/10.1007/s40265-016-0564-5.