Comparison of clinical and pathological features of secondary IgA nephropathy of ankylosing spondylitis and primary IgA nephropathy

Aim: Comparison of clinical and pathological features of secondary IgA ne-phropathy of ankylosing spondylitis (SIgAN-AS) and primary IgA nephropathy (PIgAN). Ma-terials and methods: Clinical characteristics and pathological data of patients diagnosed with IgAN by renal biopsy were collected in our hospital from January 2008 to October 2018. Patients with SIgAN-AS and PIgAN were recruited at a ratio of 1 : 5. Fifteen pa-tients with SIgAN-AS and 75 patients with PIgAN were enrolled in this retrospective study. Results: There were 15 cases in the SIgAN-AS group, including 13 males and 2 fe -males. The cohort of 75 patients with PIgAN included 37 males and 38 females. There were significantly more males in the SIgAN-AS group 13/15 (86.67%) vs 37/75 (49.30%), p < 0.05. Compared with PIgAN patients, SIgAN-AS patients had higher incidences of hematuria (12/15 (80.00%) vs. 37/75 (49.33%), p < 0.05), lower levels of 24-hour urinary protein (0.85 +/- 0.68 vs. 1.57 +/- 1.54 g, p < 0.05), but higher levels of estimated glomerular filtration rate (eGFR) (CKD-EPI formula; 112.56 +/- 24.53 vs. 88.23 +/- 29.39, p < 0.05), albumin (44.67 +/- 3.48 vs. 41.09 +/- 7.07 g/L, p < 0.05), erythrocyte sedimentation rate (ESR) (43.20 +/- 33.94 vs. 18.79 +/- 16.26 mm/h, p < 0.001), and C-reactive protein (CRP) (21.19 +/- 30.61 vs. 2.11 +/- 4.58 mg/L, p < 0.001). From the per- spective of renal pathology of PIgAN, pa-tients with SIgAN-AS had a lower incidence of renal tubular atrophy/interstitial fibrosis of nephropathy (p < 0.05). Immunohistos-taining analysis showed a higher incidence of dominant deposits of single IgA in the mesan-gial cell area (p < 0.05). Conclusion: SIgAN-AS was more commonly observed in males and displayed a milder progression than those PIgAN. The majority of SIgAN-AS patients can be improved by early intervention.