What Are Risk Factors for Developing Psoriatic Arthritis?
It is estimated that approximately 1% of the general population has psoriatic arthritis (PsA), although the exact prevalence is unknown, partly due to missed diagnoses and misdiagnoses.1,2 There are several identified risk factors for PsA: having psoriasis, having a family history of PsA and/or psoriasis, and age.3
People with psoriasis are at an increased risk of developing PsA.3 PsA occurs in up to 40% of people with psoriasis. The skin disease generally develops before the joint disease in the majority of patients. However, PsA develops before psoriasis in 10-15% of cases. Nearly all patients with PsA also have psoriasis.1
Some studies have shown that a greater body surface area involved in psoriasis is associated with an increased risk of developing PsA. However, the extent and severity of psoriasis, as quantified by the Psoriasis Area and Severity Index (PASI), do not correlate with the severity of PsA joint disease.3
Specific psoriasis symptoms that have been independently associated with PsA risk include:
- Scalp lesions – increasing the risk of PsA 3.75 times
- Nail dystrophy (damage to the nail beds) – increasing the risk of PsA 2.24 times
- Intergluteal (between the buttocks) or perianal (around the anus) lesions – increasing the risk of PsA 1.95 times3
Epidemiologic studies, which look at the distribution and cause of disease, have also shown a correlation between body mass index and the risk of PsA in psoriasis populations. In addition to being a risk factor for PsA, obesity may also reduce the effectiveness of some treatments for psoriasis and PsA. 3
Both psoriasis and PsA demonstrate high rates of occurrence in families, which suggests that both disorders have a strong genetic basis. The prevalence of PsA among first-degree relatives has been shown to be 49 times higher than the prevalence in the general population.3
PsA most often develops in people aged 35-55 years, although it can occur at any age. In the juvenile form, which is more rare, PsA typically develops at 9-11 years of age.4
Common risk factors for other autoimmune diseases
Researchers have evaluated and found several common risk factors that occur in many autoimmune disorders. One such trial determined three risk factors that were common among inflammatory autoimmune diseases: having first-degree relatives with autoimmune disease, being female, and advanced age.5 While first-degree relatives is a risk factor for PsA, age and gender do not increase risk in developing PsA.