Crohn's disease-associated IgA nephropathy may prone to better renal outcome.

Background and aim: Renal involvement in Crohn's Disease (CD) was rare in the population. Little was known between IgA nephropathy and CD. This study aimed to investigate the differences in clinical and outcome features of CD-associated IgA nephropathy (CD-IgAN) and primary IgA nephropathy (PIgAN).

Methods: Clinical data of patients diagnosed with IgAN by kidney biopsy were collected in the Sixth Affiliated Hospital of Sun Yat-sen University from January 1st, 2016 to June 1st, 2023. 17 patients with CD-IgAN and 87 patients with PIgAN were enrolled in this retrospective study.

Results: Compared with PIgAN patients, CD-IgAN patients had lower levels of urinary protein excretion (1.57 g per 24 h vs. 0.33 g per 24 h, p < 0.01), but higher levels of estimated glomerular filtration rate (77.63 ± 40.11 ml per min per 1.73m² vs. 104.53 ± 32.97 ml per min per 1.73m², p = 0.008). From the point of renal pathology of PIgAN, patients with CD-IgAN had a less incidence of tubular atrophy or interstitial fibrosis (p = 0.001). CD-IgAN patients had a higher incidence of complete remission of proteinuria (45.8% vs. 81.8%, p = 0.031) or hematuria (10.4% vs. 45.4%, p = 0.019) than PIgAN patients after twelve-month treatments.

Conclusions: CD-IgAN manifests a milder progression of renal function than those PIgAN. After the treatment, proteinuria or hematuria are more prone to remit in patients with CD-IgAN.