Anti-nephrin antibodies in minimal change disease: Case report series

Minimal change disease (MCD) is one of the causes of nephrotic syndrome (NS) in adults. Recently, anti-nephrin antibodies have been detected in a certain subset of patients with MCD, supporting the proposed autoimmune etiology and appearing to be markers of disease activity. Despite their diagnostic and prognostic potential, the use of anti-nephrin autoantibodies in routine clinical practice is not yet widespread. Studies have shown that patients with anti-nephrin-associated MCD have a more fulminant NS and a better response to antibody-depleting therapy than those who are anti-nephrin-negative.

We report cases of a 79- and a 42-year-old male patient presenting with new-onset NS and acute kidney injury. Both patients had negative immunologic tests, including antibodies against phospholipase A2-receptor (anti-PLA2R) and thrombospondin-7A (anti-THSD7A). Renal biopsy was performed in both patients.

In both cases, light microscopy of kidney samples from thick-needle biopsy showed acute tubular injury attributed to severe proteinuria. Electron microscopy revealed diffuse (90%) effacement of the podocyte foot processes without electron-dense deposits. Immunofluorescence presented discrete intracytoplasmic IgG podocyte deposits with a high probability of MCD due to anti-nephrin autoantibodies. In addition to therapy with angiotensin convertase inhibitors, calcium channel blockers, and furosemide, we started treatment with low-dose oral glucocorticoids and mycophenolic acid (case 1) or oral glucocorticoids alone (case 2) depending on patients' comorbidities. We administered rituximab, resulting in a fast and complete resolution of proteinuria and improvement of kidney function.

Anti-nephrin autoantibodies have been detected in a subgroup of patients with MCD supporting the autoimmune etiology of the disease. Targeted anti-B-cell therapy with rituximab is an additional therapeutic option in patients with relapsing or treatment-resistant disease, or drug-related adverse effects to standard therapy.