Few studies have examined the features of patients with IgA nephropathy secondary to psoriasis (IgAN-Pso); leaving the long-term renal outcomes and risk factors for this group unclear. A total of ninety patients with IgAN without evidence of a secondary cause other than psoriasis were enrolled in this retrospective study. The participants were categorized into two groups: the mild-to-moderate psoriasis group (n = 74) and the severe psoriasis group (n = 16). A comparative analysis was conducted on the clinicopathological attributes and renal outcomes between the two groups. Additionally, prognostic risk factors for end-stage renal disease (ESRD) were assessed. The patients within the severe psoriasis cohort exhibited a heightened prevalence of eGFR < 60 ml/min/1.73 m2 and urinary protein levels exceeding 1.49 g/d, alongside more pronounced T lesions and an increased incidence of C2 lesions (crescent > 25%) compared to their mild-to-moderate psoriasis counterparts. During a median follow-up period of 34.8 months, 11 patients (5 [35.7%] with severe psoriasis and 6 [8.2%] with mild-moderate psoriasis, P < 0.05) progressed to ESRD. At the time of biopsy, eGFR, CRP > 21.2 mg/l, immunoglobulin G > 8.05 g/l, low C3 and time-average proteinuria emerged as independent predictors of future ESRD. Pathological parameters could not independently predict ESRD when considering the baseline clinical features. Our study indicates that severe psoriasis is associated with worse renal impairment observed at biopsy and a greater likelihood of developing ESRD afterwards.
