medwireNews: People who suffer from chronic rhinosinusitis without nasal polyps (CRSsNP) have around twice the risk for psoriasis as the general population, a Taiwanese study has found.

The association presumably reflects shared immunologic abnormalities underlying both CRSsNP and psoriasis, write Herng-Ching Lin (Taipei Medical University, Taiwan) and fellow study authors in the British Journal of Dermatology.

Lin's team performed a retrospective cohort study using the Taiwanese Longitudinal Health Insurance Database. They identified 13,242 adults with a diagnosis of CRSsNP and matched them with 39,726 CRSsNP-free control individuals of similar gender, age, and level of urbanization.

Each participant was followed up for 5 years. During this time, 0.7% of the CRSsNP cohort and 0.3% of controls were diagnosed with psoriasis, giving incidence rates of 1.41 and 0.69 per 1000 person-years in people with and without CRSsNP, respectively.

The difference in psoriasis incidence between people with and without CRSsNP was statistically significant in unadjusted analyses, Lin et al report. Furthermore, it remained significant after adjusting for multiple confounders, with a hazard ratio of 2.01.

"This study succeeded in providing a risk estimate for subsequent psoriasis among patients with CRSsNP, thus adding large-scale population-based epidemiological evidence to the body of knowledge surrounding this association," writes the team.

They note that CRSsNP is characterized by a skewed T-helper (Th) cell 1 response and predominantly neutrophilic inflammation; similarly, psoriasis is a Th1 pathology that is frequently comorbid with other Th1 conditions.

Lin and co-authors remark: "Our study adds credence to the theory that CRS without polyps proceeds through a Th1 response, and also adds large-scale epidemiological data from a Chinese population to the prevailing Western bias regarding this association in the literature."

Free abstract