Case Report: Advanced IgA nephropathy with psoriasis and a complex clinicopathologic course

Psoriasis and IgA nephropathy are immune-mediated disorders that may coexist, but the clinical meaning of this association remains uncertain. We report a 45-year-old man with psoriasis and progressive kidney dysfunction whose biopsy-proven IgA nephropathy presented with severe impairment of kidney function, heavy proteinuria, and mixed active and chronic histologic injury. At reassessment, serum creatinine was 463 μmol/L, estimated glomerular filtration rate was 12.1 mL/min/1.73 m², and pretreatment 24-hour urinary protein excretion ranged from 2.90 to 4.70 g. Kidney biopsy showed proliferative sclerosing IgA nephropathy, Oxford classification M1E1S1T2C0, with ischemic glomerular injury, microangiopathy, tubular atrophy, and interstitial fibrosis. Targeted-release budesonide and deucravacitinib were started together. Proteinuria fell to 0.62 g, serum creatinine decreased to 323 μmol/L, and a modest improvement in cutaneous disease activity was observed, with PASI decreasing from 2.4 to 1.6. After patient-initiated discontinuation of deucravacitinib, proteinuria increased and later declined after reintroduction. Following completion of the planned budesonide course, proteinuria continued to fall during deucravacitinib monotherapy, while kidney function deteriorated. This case is best interpreted as a clinicopathologic observation rather than proof of drug efficacy. Biopsy-defined activity and chronicity helped explain the discordant changes in proteinuria and kidney function, while the longitudinal course generated a testable but unproven hypothesis of a possible inflammatory connection between psoriasis and IgA nephropathy.