Psoriatic arthritis (PsA) is a chronic inflammatory condition affecting individuals with psoriasis, a skin disease characterized by red patches and silvery scales. This immune system disorder leads to pain, swelling, and stiffness in the joints, impacting fingers, toes, and the spine. While psoriasis often appears first, joint issues can begin simultaneously or even before skin symptoms.
The Hereditary Connection
Psoriatic arthritis is not inherited simply, like single-gene disorders. Instead, genetic predisposition means certain genetic factors increase an individual’s likelihood of developing the condition. This is evidenced by familial aggregation, where PsA occurs more frequently within families.
About 33% to 50% of individuals with psoriatic arthritis have a close relative with PsA or psoriasis, suggesting genetics contribute approximately 80% to its heritability. PsA is a complex genetic condition, meaning multiple genes, not a single one, interact to influence its development.
Key Genes Involved
Specific genetic markers increase the risk of developing psoriatic arthritis. Associated with the human leukocyte antigen (HLA) region on chromosome 6, HLA-B genes are particularly relevant. HLA-B27 is more strongly associated with PsA, especially in individuals with spinal manifestations.
Other HLA alleles, such as HLA-B38 and HLA-B39, also increase PsA risk. Beyond the HLA region, other susceptibility genes involved in immune system function or inflammatory pathways have been identified through genome-wide association studies (GWAS). These include IL12B, IL23R, TNIP1, and TRAF3IP2. Possessing these genetic markers increases risk but does not guarantee PsA development.
Environmental Triggers and Other Risk Factors
While genetics contribute to PsA likelihood, environmental factors often trigger symptoms in genetically predisposed individuals. Infections, such as streptococcal infections, can initiate or worsen psoriatic disease. Physical trauma, including injuries to the skin or joints, is another environmental trigger, which can lead to new skin lesions or joint inflammation (Koebnerization).
Certain medications can also trigger symptoms. Other non-genetic risk factors contribute to PsA development. Obesity is a risk factor, linked to a higher likelihood of developing PsA. Smoking has also been linked to an increased risk of PsA and can interfere with treatment effectiveness. Stress and certain gut issues can also contribute to both the onset and flares of psoriatic arthritis.
Understanding Your Family Risk
A family history of psoriatic arthritis or psoriasis indicates an increased personal risk, but it does not mean an individual will definitely develop the condition. Knowing this family history can encourage earlier vigilance for symptoms.
Individuals with a family history should be aware of early signs of PsA, including:
- Joint pain, stiffness, and swelling in one or more joints, often worse in the morning.
- Nail changes, such as pitting, crumbling, or separation from the nail bed.
- Swelling of entire fingers or toes, or dactylitis.
- Pain where tendons and ligaments attach to bones, particularly around the heel (Achilles tendinitis) or sole of the foot (plantar fasciitis).
If any of these symptoms appear, consulting a healthcare professional is advised promptly for early diagnosis and management, which can help control symptoms and prevent joint damage.