Abstract: TH-PO196

Incidental Thin Basement Membrane Associated with Primary Membranous Nephropathy

Session Information

Category: Nephrology Education

  • 1302 Fellows and Residents Case Reports

Authors

  • Naranjo Sanchez, Felipe, North Shore Medical Center, Salem Hospital, Cambridge, Massachusetts, United States
  • Rennke, Helmut G., Brigham and Women's Hospital, Boston, Massachusetts, United States
  • Burdge, Kelly A., North Shore Medical Center, Salem Hospital, Cambridge, Massachusetts, United States
Background

Thin basement membrane nephropathy (TBMN) is a benign recessive genetic condition caused by defects of α3 or α4 type IV collagen, presenting with hematuria. A thin BM can also be found in Alport syndrome, an x-linked disease affecting α5 type IV collagen, which presents with early renal failure and has poor prognosis.

Methods

52 yo F, PMHx of HTN, CKD3, GERD and Takasubo cardiomyopathy, presented to the ER with severe headache and nausea, there she had one episode of seizure, lasting 45 secs, in the setting of PRES. In her workup, a UA demonstrated proteinuria, confirmed to be 8g/g creatinine in a random sample, but no hematuria. Medications included: amlodipine, lisinopril, metoprolol, atorvastatin and omeprazole. She denied NSAIDs, herbal or illicit drugs, smoking, travel. No family history of kidney or autoimmune diseases. She had negative cervical, breast and colon cancer screening. Physical exam demostrated stable vital signs and edema in lower extremities. Urine sediment findings: few muddy brown casts and several fat bodies. Laboratory showed: SCr 2 mg/dl (previous 1mg/dl); hypercholesterolemia, hypoalbuminemia, Alb/Cr 8,583 mg/g; negative serology for HBV, HVC, HIV and RPR; normal C3 and C4, negative ANCA, ANA, SPEP and positive PLA2r antibody; low IgG, normal IgA. Kidney biopsy reported membranous glomerulonephropathy (MGN) stage II. Immunofluorescence microscopy revealed co-dominant reactivity for IgG3 and IgG4, weakly reactive to PLA2r. Electronic microscopy showed diffuse attenuation and fraying of lamina densa and effacement of foot processes of the glomerular basement membrane (GBM); thickness of the GBM could not be measured due to marked distortion of the capillary wall; changes suggestive of TBMN, an inherited abnormality of the GBM, possibly involving collagen IV genes. Patient was started on rituximab, cyclophosphamide and steroids, with improvement Alb/Cr ratio to 89 mg/g.
The underlying etiology for her proteinuria was primary MGN, but a concomitant TBMN was incidentally observed, probably heightened the primary glomerular disease.

Conclusion

Diagnosing female patients with TBMN should raise awareness to screen for GBM collagen-related inherited disorders in the patient’s family members, especially in males. Careful clinical assessments and repeated urinalysis should be offered to discover the genetic basis of the disease.