Editorial to article: “Clinico-pathologic relationship in Colombian patients with lupus nephritis”

In the article by Velásquez-Franco et al.,¹ the authors describe a series of patients with lupus nephropathy and attempt to establish correlations between the clinical, analytical and immunological parameters and the data from renal biopsy. After the statistical analysis, they only found a clinical-pathological association between the proliferative forms and the presence of hematuria, 24 h proteinuria, level of serum creatinine and C3 hypocomplementemia. The authors conclude that renal biopsy continues to be the gold standard for the diagnosis and the correct evaluation of patients with suspected lupus nephropathy.

An important number of studies on this field (reviewed in the discussion section of the article by Velásquez-Franco et al.) have been published and have tried to establish different relationships in order to avoid the performance of renal biopsy, which is not exempt from possible complications. The result, in general, is similar in all of them, although with important differences. Globally, the proliferative forms are characterized by a greater immunological activity with a clinical presentation in the form of nephritic syndrome, in most cases, while the non-proliferative and membranous forms in particular, would occur with practically normal complement levels and the nephrotic syndrome would be the predominant clinical picture.² However, the article by Velásquez-Franco et al.¹ is a clear example, there are cases that to not follow these conditions. The discordant results might be due to the number of patients included in each of the studies, their ethnic origin, the limitation of the renal biopsy itself in which the number of glomeruli is sometimes not representative of the existing lesion, or to the inclusion of mixed forms (proliferative and membranous). In short, the problem points out the lack of a biomarker with enough sensitivity and specificity, not only for the diagnosis of lupus nephropathy but for the different histological types thereof and that makes renal biopsy to constitute the reference test for the diagnosis and treatment of lupus nephropathy. Derived from the information that it provides, on the one hand it allows to rule out other etiologies that might be present in patients with lupus and renal affectation, such as thrombotic microangiopathy in the presence of antiphospholipid antibodies, or endocapillary proliferative or membranoproliferative glomerulonephritis in cases of acute kidney failure.³ Secondly, it allows to evaluate the severity of the condition through the calculation of the activity and chronicity indexes in the proliferative forms and, finally, it provides information on lesions that although they are not contemplated in the classification of lupus nephropathy of 2003, are important for the treatment of some of its manifestation such as proteinuria in case of podocytopathy, tubulointerstitial lesions or renal vascular lesions.⁴ In this sense, the coexistence of some of these lesions could be another reason for the lack of association between the clinical parameters and the anatomopathological findings of renal biopsy.

Therefore, in case of suspicion of lupus nephropathy, renal biopsy is recommended in the current KDIGO, ACR, EULAR/ERA-EDTA and SEMI's guidelines to confirm the diagnosis, to evaluate its severity through the activity and chronicity indexes, and to decide the most appropriate treatment.⁵