Background/Purpose: To assess acute thrombotic microangiopathy (aTMA) and chronic vascular lesions (cTMA) in lupus nephropathy and to evaluate their association with extrarrenal lupus features, antiphospholipid (APS) clinical and/or serological criteria, low complement and renal survival.

Methods: We studied consecutive lupus patients (2008-2012) according to the following inclusion criteria: renal biopsy, at least two determinations of  aCL (IgG-IgM), anti-b₂GP-I (IgG-IgM), lupus anticoagulant and ≥1 year of post-biopsy follow-up. We excluded patients with overlap syndromes, diabetes mellitus, uremic hemolytic syndrome, thrombotic thrombocytopenic purpura and malignant hypertension. A blinded nephropathologist evaluated all biopsies. aTMA was defined as a fibrin thombi in arterioles and glomeruli and cTMA as arterial fibrous intimal hyperplasia and/or organized thrombi and/or fibrous occlusion and/or subcapsular ischemic cortical atrophy. We retrospectively collected demographic and clinical data (lupus and APS features, immunosuppressors and anticoagulant use), hypocomplementenemia as well as renal survival assessed as chronic dialysis. We used X², t-student and U-Mann Whitney test, plotted survival curves and Cox regression analysis. 

Results: We studied 90 lupus kidney biopsies from patients with disease duration at the time of the biopsy of 5.9 years and a median post-biopsy follow-up 2.4 of years (range 1-6.5). Eleven patients (12.2%) had cTMA and 3 (3%) aTMA. There were no differences in age, lupus duration, hypertension, immunosuppressors use, extra-renal lupus features (arthritis, vasculitis, serositis, hematologic, neurologic, Raynaud, cutaneous) and APS prevalence between patients with cTMA or without cTMA. We did not find any difference in the presence of low C3 (63% vs. 62%), low C4 (72% vs. 73%) nor in the frequency of aCL IgG  (27% vs 30%), anti-β₂GP1 IgG (36% vs 46%), anti-β₂GP1 IgM (22% vs 40%) and AL (20% vs13%) among patients with and without cTMA, respectively. Patients with cTMA had less frequently aCL-IgM (27% vs 66%, p=0.02), a higher prevalence of chronic dyalisis (54.5% vs 24% p=0.06), a higher frequency of class IV nephropathy  (100% vs 40%, p=0.01) also with a higher activity index (7.5 vs 2, p=0.03). At four years of follow-up, 28% of cTMA patients and 62% non-cTMA patients were free of dialysis (log Rank p=0.03). At the Cox analysis, cTMA  was associated with chronic dialysis (RR 2.9, CI 95% 1.1-8.1, p=0.03).

Conclusion:  cTMA confered a poor renal outcome. Unlike published studies, cTMA was not associated with lupus or antiphospholipid clinical or serological features. Other factors hitherto not studied are involved in the pathogenesis of this histopathological feature.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/thrombotic-microangiopathy-and-poor-renal-outcome-in-lupus-patients-is-not-associated-with-antiphospholipid-syndrome-andor-other-lupus-conventional-features/