Abstract: TH-PO184

A Sheep in Wolf’s Clothing: Hematuria in GPA

Session Information

Category: Nephrology Education

  • 1302 Fellows and Residents Case Reports

Authors

  • Hemmings, Stefan Ceru, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
  • Geetha, Duvuru, John Hopkins Bayview Medical Center, Baltimore, Maryland, United States
  • Segal, Paul E., Johns Hopkins Bayview Medical Center, Baltimore, Maryland, United States
  • Sozio, Stephen M., Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
Background

Performing a renal biopsy in a patient with RBC casts, rising serum creatinine (sCr) and positive ANCA serology is justifiable to evaluate for crescentic glomerulonephritis and determine best management strategies. Nonrenal involvement has a better prognosis in patients with ANCA-vasculitis. Finding underlying unrelated benign pathology in such instances can make future clinical decision-making challenging.

Methods

A 51 year-old man visited the rheumatology clinic in May 2017 for ongoing unexplained multisystem symptoms. He had been in good health until 10 months earlier when he started having recurrent bouts of sinusitis, cough, fatigue, otitis media leading to deafness and a 40lbs weight loss. Serology for cANCA was positive [1:40 titer; PR3: 87], this was negative earlier in his clinical course. He was noted to have microscopic hematuria and was seen in nephrology clinic within 24 hours for evaluation. His sCr notably had risen from 0.7 to 1.0 mg/dL over a 5 month-period, he had normal serum complements, and his random urine protein to creatinine ratio was 280 mg/g. Urine microscopy revealed RBC casts (Figure-left). An urgent renal biopsy was performed and pulse IV steroids initiated for presumed renal involvement of granulomatosis with polyangiitis (GPA). On biopsy, the 19 glomeruli sampled were histologically normal on light microscopy and immunofluorescence was unremarkable. Electron microscopy revealed thin basement membranes of width 218nm (Figure-right). Alport’s immunostaining was negative.

Conclusion

Thin Basement Membrane Nephropathy (TBMN) likely explained his microscopic hematuria and RBC casts. This diagnosis portends a good clinical renal prognosis. However, finding benign pathology, including TBMN, does pose challenges in diagnosing a GPA relapse clinically as the hematuria and RBC casts can be intermittent and from the benign condition. Nevertheless, this case highlights the utility of performing renal biopsy even when there is a high index suspicion of renal involvement from ANCA-associated vasculitis.

RBC cast on microscopy (Right) and Electron Microscopy with TBMN (Left).