[A comparative study of IgA nephropathy secondary to ankylosing spondylitis and primary IgA nephropathy]

To study the characteristics of IgA nephropathy (IgAN) secondary to ankylosing spondylitis (AS) compared with primary IgAN.

Clinical and pathologic data were collected in patients who were diagnosed with IgAN by renal biopsy and admitted to our hospital from Jan 2007 to Sep 2015. Patients with IgAN secondary to AS were recruited by the ratio 1:5 of patients with primary IgAN as control group at the same period.

There were 15 patients in AS group, proportionately 75 patients in the control group. Compared with those in control group, patients in AS group had shorter disease course [(10.1±8.3) months vs (20.2±27.9) months] and lower proportions of renal insufficiency and hypertension[1/15 vs 52.0%(39/75); 1/15 vs 46.7%(35/75)]. In laboratory tests, quantitative 24 hour urinary protein and serum creatinine were significantly lower in group AS than those in the control group [(1.42±0.67)g vs (2.88±1.35)g; (79.0±18.2)mmol/L vs (145.3±77.6) mmol/L]. The Lee grading of IgAN in two groups was comparable. The treatment in both groups was similar including steroids, immunosuppression agents, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers . After follow-up from 1 to 6 years, 3/11 patients in AS group and 22.8%(13/57)(13/75) in control group developed deterioration of renal function.

Patients with IgAN secondary to AS have shorter disease course and milder condition compared with patients with primary IgAN. Clinical outcome of renal function in both groups is similar according to comparable treatment.