Abstract: TH-PO221

The “M” Factor: An Insight into IgM Nephropathy

Session Information

Category: Nephrology Education

  • 1302 Fellows and Residents Case Reports

Authors

  • Malhotra, Divyanshu, Yale New Haven Hospital, New Haven, Connecticut, United States
  • Luciano, Randy L., Yale New Haven Hospital, New Haven, Connecticut, United States
Background

Nephrotic syndrome is an important clinical entity with multiple manifestations and a variety of causes. In addition to MCD, three other disorders causing a picture of nephrotic syndrome present initially with minimal changes on light microscopy. These include idiopathic mesangial proliferative glomerulonephritis, IgM nephropathy and C1q nephropathy. There is a controversy regarding these being a part of the spectrum of MCD/FSGS versus being separate clinical entities. We present a series of 2 patients with IgM nephropathy and their interesting clinical course.

Methods

Case 1
61 y/o male with DM who had initially presented with lower extremity edema, scrotal swelling and was found to have 3+ proteinuria. His further w/u revealed Hepatitis C Genotype 1b infection. He had a kidney biopsy which was consistent with IgM nephropathy and early diabetic nephropathy. Initially it was thought that this was secondary to the hepatitis C. He received Ledipasvir/Sofosbuvir for the Hepatitis C with SVR. This led to proteinuria resolution but recurrence in 3 months. Started on prednisone which controlled the proteinuria but with recurrence when he tapered off steroids. He had a another biopsy which showed evidence of IgM nephropathy again. He was then started on Cellcept and currently remains in remission on the same.
Case 2
22 y/o male who came to our clinic with a diagnosis of FSGS and nephrotic syndrome. He had been steroid dependent with frequent relapses off prednisone. Repeat biopsy showed evidence of IgM nephropathy concomitant with FSGS. He was switched to Cellcept leading to remission but with relapse requiring steroids. His course waxes and wanes on cellcept and we have planned for an extended genetic testing panel for podocyte specific genes.

Conclusion

IgM nephropathy is a rare condition and has been a controversial entity since its first description. It is characterized by prominent diffuse mesangial deposits of IgM +/- complement, along with electron dense deposits in the mesangium. Limited case series suggest that it is typically more steroid resistant than idiopathic MCD. Progression to FSGS is possible in a number of cases. Exact pathophysiology and relationship to FSGS is not well defined. Clinical progression is intermediate between MCD and FSGS. Multiple steroid sparing immunosuppressants have been tried with variable responses thus it can be a challenging disease to manage as seen in our cases too.