Abstract
This study aimed to determine the impact of HLA-B27 on clinical phenotype and renal function during follow-up periods in patients with ankylosing spondylitis (AS) and secondary IgA nephropathy (IgAN). This single-center retrospective study included 71 AS patients with secondary IgAN. Renal function decline was defined as a mean eGFR decline of more than 5 mL/min/1.73 m2 per year or progression into the dialysis stage. The association between HLA-B27 status and renal function decline was evaluated by univariable and multivariable Cox regression analyses. The results showed that seven (9.85%) of the 71 included patients were HLA-B27-negative. The median follow-up period was 4.0 years. HLA-B27-negative patients showed higher levels of uric acid (UA) than those who were HLA-B27-positive. Pathologically, a higher percentage of globally sclerotic glomeruli was observed in HLA-B27-negative patients. Survival analysis indicated that HLA-B27 negativity was associated with a significantly higher probability of renal function decline than HLA-B27 positivity. This significant association was also found in subgroup analyses of patients with either substantial proteinuria (more than 1.0 g per day) or interstitial fibrosis and tubular atrophy. Multivariable analysis showed that HLA-27 negativity was independently associated with renal function decline (HR 6.58; 95% CI 1.65 to 26.21; p = 0.008). In conclusion, HLA-B27 negativity is associated not only with a higher level of UA and a higher percentage of globally sclerotic glomeruli in AS patients with secondary IgAN but with renal function decline during follow-up periods.
Highlights
Ankylosing spondylitis (AS) is a chronic inflammatory disease predominantly affecting the spine, sacroiliac joints, and peripheral joints, which may lead to disability
A history of mucosal infections is characteristic of typical ankylosing spondylitis (AS) and IgA nephropathy (IgAN) patients, in whom the clinical symptoms emerge about several weeks postinfection [10]
IgA immune complex was detected in some AS patients, which is consistent with the proposed mechanism of IgAN in which circulating immune complexes lead to mesangial IgA deposition and renal tissue damage [11, 12]
Summary
Ankylosing spondylitis (AS) is a chronic inflammatory disease predominantly affecting the spine, sacroiliac joints, and peripheral joints, which may lead to disability. In addition to extra-articular manifestations such as uveitis, psoriasis, and inflammatory bowel disease (IBD), some other organ systems may be involved [1,2,3]. Renal involvement is an uncommon but significant complication that contributes to the poor prognosis of AS patients [4]. The most common pathological type of renal lesions in AS is IgA nephropathy (IgAN), the diagnosis of which mainly depends on renal biopsy. IgAN is characterized by deposition of immune complexes in the glomerular mesangium, proliferation of mesangial cells, increased synthesis of extracellular matrix, and infiltration of proinflammatory. The clinical manifestations of IgAN include proteinuria, microscopic hematuria, and hypertension, alone or in combination. There is little knowledge about the clinical features and prognosis in this unique patient population owing to the requirement for pathological evidence
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