Recent advances in human genetics empower researchers to discover the genetic basis of many common disorders. As genetic science is evolving at a rapid pace, new discoveries are made almost daily.

PsoriasisDX is committed to providing the latest in genetic discoveries to patients and their doctors. While it is clear that multiple genes play a strong role in the development of psoriasis and psoriatic arthritis (PsA), the causative genes have not yet been fully characterized (1).

Scientists believe that psoriasis and PsA share common susceptibility genes, since a significant proportion of psoriasis patients and their first degree relatives develop PsA (1,2). Given that the immune system is involved in the pathogenesis of both diseases, it is not surprising that variations in immune response genes have shown the strongest association with psoriasis and PsA (1,2).

The immune response genes are among the most polymorphic in the human genome. The gene encoding the HLA class I antigen HLA-Cw6 is the primary susceptibility locus for developing type I psoriasis (3). This gene is also associated with PsA; however, it is not independently associated with PsA.

The strongest independent genetic association for PsA is found in the immune response gene, MICA, located on chromosome 6. In particular, a triple repeat polymorphism in the MICA gene (called MICA-A9) is found in approximately 60% of patients who develop PsA. The MICA-A9 association was replicated by four peer-reviewed and published studies involving over 900 patients from multiple ethnic populations (4-7).

The PsoriasisDX genetic screening test reports on the presence or absence of the MICA-A9 allele. According to the published studies, a patient with a positive test result has approximately 60% chance of developing PsA, while a patient with a negative test result has approximately 70% chance of not developing PsA.

The need for early screening and medical intervention for PsA is underscored by the fact that PsA becomes more severe when left untreated, leaving patients with significant joint damage, functional impairment, and reduced quality of life. Approximately 20% of PsA patients develop a debilitating form of arthritis (8).

FDA approved medications for the treatment of PsA are most effective at controlling inflammation and arresting joint destruction, but are ineffective at reversing joint damage; therefore, it is important to identify psoriasis patients at high risk for developing PsA prior to the onset of arthritic symptoms.

Current PsA screening techniques identify symptomatic patients after the onset of inflammatory arthritis. Identifying PsA in an earlier or pre-clinical stage will allow treatment to be initiated at a time when intervention has a greater likelihood of succeeding. Early screening combined with tailored treatment will help prevent disease progression and slow joint destruction.

WARNING: Due to the limitations of the test to identify all the psoriasis patients that will ultimately develop PsA, the PsoriasisDx Genetic Test for PsA should be used as an adjunct to currently used diagnostic criteria to determine the need for medical therapy. In particular, patients carrying the high risk MICA-A9 allele who already show any signs of inflammatory arthritis and who have psoriasis or a family history of the disease will likely need an aggressive treatment plan determined by a qualified doctor to slow the progression of PsA.

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