Comparison of clinical characteristics and outcome between isolated and classic lupus nephritis

Background/Purpose: Lupus nephritis (LN) is a serious manifestation of systemic lupus erythematosus (SLE). Rarely, patients may present with LN alone and have no extra-renal clinical manifestations of lupus (isolated lupus nephritis, ILN). We aimed to describe the clinical characteristics of patients presenting with isolated LN and to study their treatment outcome and long term survival and its predictors compared to classic LN.

Methods: Subjects were identified by searching a pathologic renal biopsy database. Clinical records were reviewed for exclusion of infectious and secondary causes. Cases with isolated LN were defined per 2012 SLICC criteria; classic SLE patients had lupus nephritis along with extra-renal manifestations of lupus. Complete response (CR) was defined as proteinuria <0.5 g/24 h and serum creatinine (sCr) within 125% of the baseline value after the start of induction therapy. Partial response (PR) was defined as reduction of proteinuria of >50% (and at least <3.0 g/24 hours) plus sCr within 125% of the baseline value after the start of the induction therapy.

Results: 30 patients with isolated LN and 134 patients with classic LN were identified. The median age at the time of biopsy was 41 and 39 years, for the ILN and LN group, respectively. Majority were Caucasian; female to male ratio was 3:1 in ILN and 2:1 in the LN group. The median duration from renal symptoms to biopsy was 5.2 months for ILN and 1.2 for the LN group (p=0.013). Mean sCr was 1.7 mg/dl and 1.3 mg/dl and 24 hour proteinuria 8.5 and 4.9 g, respectively. A greater percentage of patients with ILN had hypertension at onset (83% versus 35% in LN, p<0.001) and interstitial fibrosis in biopsies (97% ILN versus 69% LN, p=0.018). The outcomes and survival among 18 ILN and 72 LN patients of class 3, 4 or mixed are noted in Table.

Conclusion: The response rates and 10 year survival tended to be higher in the LN group compared to ILN. Possible late recognition and/or under treatment of this subset may be underlying the differences.