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

Abstract

Comparison of clinical and pathological features of secondary IgA nephropathy of ankylosing spondylitis (SIgAN-AS) and primary IgA nephropathy (PIgAN). 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 patients with SIgAN-AS and 75 patients with PIgAN were enrolled in this retrospective study. There were 15 cases in the SIgAN-AS group, including 13 males and 2 females. 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±1.54g, 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±16.26mm/h, p<0.001), and C-reactive protein (CRP) (21.19±30.61 vs. 2.11±4.58mg/L, p<0.001). From the perspective of renal pathology of PIgAN, patients with SIgAN-AS had a lower incidence of renal tubular atrophy/interstitial fibrosis of nephropathy (p<0.05). Immunohistostaining analysis showed a higher incidence of dominant deposits of single IgA in the mesangial cell area (p<0.05). 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.