Schnitzler syndrome complicated by membranous nephropathy

Area of Science:

• Nephrology
• Immunology
• Rheumatology

Background:

• Schnitzler syndrome is a rare autoinflammatory disease characterized by chronic urticarial rash and monoclonal IgM gammopathy.
• The association between Schnitzler syndrome and kidney disease is not well-established.

Observation:

• A 62-year-old male with Schnitzler syndrome presented with nephrotic syndrome.
• Renal biopsy revealed histological features consistent with secondary membranous nephropathy.

Findings:

• Immunofluorescence showed immunoglobulin G deposition along glomerular capillary walls.
• Electron microscopy identified subepithelial and mesangial electron-dense deposits.
• This represents the first reported renal biopsy in a patient with Schnitzler syndrome.

Implications:

• Schnitzler syndrome can be associated with secondary membranous nephropathy.
• Corticosteroid treatment effectively resolved rash and proteinuria, though IgM paraprotein persisted.
• This case highlights the importance of considering renal involvement in Schnitzler syndrome.