Proteinuria is a key to suspect autoimmune nodopathies

Area of Science:

• Neurology
• Immunology
• Nephrology

Background:

• Autoimmune nodopathies concurrent with nephrotic syndrome are increasingly reported.
• Proteinuria is being investigated as a potential biomarker for autoimmune nodopathies.

Purpose of the Study:

• To determine if proteinuria can serve as a biomarker for autoimmune nodopathies.
• To investigate the association between proteinuria and specific autoantibodies in patients with chronic inflammatory demyelinating polyneuropathy (CIDP).

Main Methods:

• Retrospective analysis of urinalysis results from 69 CIDP patients.
• Measurement of autoantibodies against paranodal proteins (contactin 1, neurofascin 155, contactin-associated protein 1) and nodal protein (neurofascin 186) using ELISA.
• Grading of proteinuria based on urine dipstick test results.

Main Results:

• Four patients (6%) tested positive for anti-CNTN1 IgG4 antibodies; five (7%) for anti-NF155 IgG4 antibodies.
• Proteinuria (mild or greater) was observed in patients with anti-CNTN1 IgG4 and anti-NF155 IgG4 antibodies.
• Autoantibody-positive patients showed a higher frequency of proteinuria compared to seronegative patients (p=0.01).

Conclusions:

• Proteinuria is a potential biomarker for autoimmune nodopathies targeting contactin 1 (CNTN1) or neurofascin 155 (NF155).
• Urinalysis is crucial for differentiating autoimmune nodopathies from CIDP.
• Testing for anti-CNTN1 IgG4 antibodies in nephrotic syndrome and anti-NF155 IgG4 antibodies in mild proteinuria is recommended.