Abstract: SA-PO373
Monoclonal Gammopathy of Renal Significance: Not Just a Disease of the Old
Session Information
- Genetic and Diagnostic Trainee Case Reports
November 09, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Trainee Case Report
- 1602 Pathology and Lab Medicine: Clinical
Authors
- Roehm, Bethany, Tufts Medical Center, Boston, Massachusetts, United States
- Varga, Cindy, Tufts Medical Center, Boston, Massachusetts, United States
- Inker, Lesley, Tufts Medical Center, Boston, Massachusetts, United States
Introduction
Immunotactoid glomerulopathy is a rare finding on kidney biopsy, reported in 0.06-0.1% of biopsies. It is characterized by subepithelial and subendothelial microtubules made of immunoglobulin deposits. Without clinical findings suggestive of lupus or cryoglobulinemia, monoclonal gammopathy of renal significance (MGRS) should be considered. MGRS can be caused by any B cell or plasma cell clonal proliferative disorder. Less than 2% of those diagnosed with monoclonal gammopathy of undetermined significance (MGUS) are under the age of 40 years. Of all patients with MGUS, 1.5% have MGRS.
Case Description
This is a 26 year old man who presented for evaluation of proteinuria and hematuria, found incidentally during work-up for an acute episode of diarrhea that subsequently resolved. Initial UPCR and UACR were 977 mg/g and 740 mg/g, respectively. Past medical history was notable only for “ear problems” requiring Eustachian tubes as a child. He was not on any medications or supplements. Blood pressure was 143/89, but there were no other abnormalities on physical exam. Complements, anti-dsDNA Ab, and CBC were normal. eGFR was 125 ml/min/1.73m2. SPEP and UPEP were not initially done as he was deemed low risk for harboring a plasma cell dyscrasia at his age.
Kidney biopsy showed immunotactoid glomerulopathy with dominant IgG Kappa. SPEP and UPEP with IFE were then done and neither showed any monoclonal bands. Bone marrow biopsy showed rare polytypic plasma cells with a small kappa-restricted plasma cell population on flow cytometry. Given his young age and the natural history of MGRS, the plan is to treat with plasma cell directed chemotherapy.
Discussion
MGRS can occur in younger patients presenting with proteinuria. When evaluating young patients with proteinuria, a broad differential should be considered. The most common causes in adults are diabetes, amyloidosis, lupus, minimal change disease, membranous nephropathy, and FSGS. We also considered IgA nephropathy and Alport’s syndrome. MGRS was low on our differential, yet kidney biopsy showed immunotactoid glomerulopathy due to MGRS despite negative SPEP and UPEP. Kidney biopsy was key in obtaining a diagnosis in our patient. It is important even in young patients not to rule out potentially treatable causes of kidney disease based on age.