Renal histopathological changes and clinical characteristics of antiphospholipid nephropathy in lupus nephritis patients

Objective
The aim of the present study was to evaluate the renal histopathological changes and clinical characteristics associated with antiphospholipid nephropathy (APSN) in lupus nephritis (LN) patients.
Patients and methods
This study included 50 LN patients referred for renal biopsy. Patients underwent clinical and laboratory assessments for disease activity and damage. The biopsy specimens were classified according to the International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification, activity, and chronicity indices, and assessed for renal vascular lesions of APSN - acute (thrombotic microangiopathy) and chronic (fibrous intimal hyperplasia, fibrous arterial/arteriolar occlusion and focal cortical atrophy).
Results
APSN lesions were found in 17/50 patients (34%); furthermore, 7/50 patients (14%) had thrombotic microangiopathy lesions, whereas chronic APSN lesions were detected in 15/50 patients (30%). LN patients with APSN had significantly higher age and Systemic Lupus International Collaborating Clinics scores ( = 0.032 and 0.004, respectively), but there were no differences in renal and antiphospholipid syndrome manifestations. Lupus anticoagulant positivity was significantly more frequent in patients with APSN ( = 0.002). LN patients with APSN had significantly higher renal chronicity scores ( = 0.033) with more frequent interstitial fibrosis and tubular atrophy ( = 0.006 for each). There was no significant difference in the distribution of LN classes in patients with and without APSN.
Conclusion
APSN is frequently found in LN patients irrespective of the LN class and antiphospholipid syndrome manifestations. It is associated with lupus anticoagulant positivity, higher disease damage, and renal biopsy chronicity indices, particularly interstitial fibrosis and tubular atrophy. Only the identification of intrarenal vascular lesions could characterize these patients, thus is it not time to revisit the ISN/RPS classification of LN to include renal vascular lesions of APSN.