A cohort analysis from Toronto suggests that axial psoriatic arthritis (PsA) is distinctly different from axial ankylosing spondylitis (AS) with psoriasis.

Researchers examined two PsA and AS cohorts –  patients with PsA with axial disease and isolated axial patients with AS with psoriasis. 

From a total of 1576 PsA patients, 2% had isolated axial disease and 29% had axial and peripheral disease. They found that isolated axial disease was associated with HLA-B*27 positivity (OR 25) and lower Health Assessment Questionnaire scores (OR 0.004).  The presence of HLA-B*27 predicted peripheral disease development over time (HR 7.54).

From a total of 1688 AS patients, the found 4.86% with axial disease with psoriasis. The latter patients (isolated axial disease with PsA) were older at diagnosis (OR 1.06), had more nail lesions (OR 12.37) and less inflammatory back pain (OR 0.12) compared to isolated axial AS with psoriasis.

Isolated axial PsA and AS with psoriasis are uncommon and are clinically distinct from each other.

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