MO223MEMBRANOUS NEPHROPATHY ASSOCIATED TO ANKYLOSING SPONDYLITIS: CASE REPORT
Authors: LAMRI Aldjia 
Published: May 2021

Abstract

Background and Aims
Ankylosing Spondylitis (AS) is a chronic inflammatory rheumatic disease diagnosed by the presence of the HLA-B27 antigen with joint and extra-articular manifestations.
Its pathogenesis was initially based on auto-inflammatory phenomena, mainly involving innate immunity. However, many studies carried out in the recent years focus on its adaptive immunity aspect, especially autoimmune. These mechanisms seem to interact with each other, resulting in a complex pathophysiology.
The general autoimmune characteristics of AS were investigated by Yuan and al, who reviewed recent reports of autoantibodies levels in AS patients. Their analysis shows that none of the autoantibodies considered in the study meet the criteria to be considered as a biomarker for the disease (including antibodies Anti- :CD74; beta2-Microglobulin; mutated Citrullinated Vimentin (MCV); Heat Shock Protein 65 (HSP65); 14-3-3 eta autoantibodies (14-3-3η); 1A-dependent autoantibody magnesium anti-protein phosphatase (PPM1A); sclerostin (SOST); and Anti-microbial antibodies).
Renal involvement in AS is dominated by amyloidosis and IgA nephropathy. In rare cases, this disease has been associated with Membranous Nephropathy (MN). The pathogenetic link between the two disorders remains obscure. However, the recent connection of AS to autoantibodies potentially indicates the involvement of immune complexes formed from these autoantibodies in the development of MN.

Method
We report the case of a 36-years-old woman with a 7 years history of sacroiliitis, who also developed a pedal edema in May 2020.
AS was diagnosed in 2014 by the presence of positive HLA-B27, and clinical and radiological manifestations of bilateral sacroiliitis without extra renal manifestations treated by indometacin during periods of pain . A pure nephrotic syndrome was revealed with a 24h proteinuria of 12g / 24h.The patient’s Albumin levels were at 16g/l, without HTA or hematuria, and with a correct renal function (Creatinine at 60mmol/l). A renal biopsy showed a MN with type I polytypical. Light microscopy showed a thickening of capillary loops, while IF staining revealed granular deposits of IgG along the capillary wall. Investigations of further secondary MNs were negative, and the patient was aPLA2R-negative.

Results
A treatment by corticosteroids was initiated prior biopsy to her referral , which resulted in pain relief and urinary protein reduction (prot 24h 1.5g/24h). Given her good response to this initial treatment, corticotherapy was maintained. As the levels of inflammation and discomfort were low, the patient did not wish to be treated by biotherapy.

Conclusion
This case suggests a secondary MN in association with AS.The discovery of new autoantibodies associated with AS opens up promising perspectives, and could potentially lead to the characterization of biomarkers for screening and monitoring this disease. However, more studies are needed in order to improve our understanding of the role played by possible immune complex diseases, (in particular MN), in relation to this Ankylosing spondilitis.