C1q Nephropathy in the Renal Allograft: A Report of 20 Cases
SM Said, LD Cornell, ME Fidler, S Sethi, SH Nasr. Mayo Clinic, Rochester, MN
Background: C1q nephropathy (C1qN) is an uncommon glomerular disease characterized by dominant or co-dominant mesangial staining for C1q in pts with no evidence of SLE. There are no series in the literature addressing the clinical and pathologic characteristics of pts with C1qN in the renal allograft.
Design: We identified and analyzed 20 cases of C1qN in renal allograft from our nephropathology archives, between 1998-2009.
Results: 80% of pts were whites and the M:F ratio was 1.5. The mean age at transplant was 30 yrs. The native disease was PCKD (35% of pts), FSGS (15%), HTN (10%), ANCA GN (10%), IgAN (10%), anti-GBM disease (5%), solitary kidney (5%), renal hypoplasia (5%) and oxalosis (5%). The kidney source was a living donor in 75% of pts and a deceased donor in 25% of pts. The mean time from transplant to diagnosis of C1qN was 44 mos (range 0.1-241 mos; >12 mos in 80% of pts). 45% of pts had preceding infection (most commonly urinary tract infection). None of the pts had clinical or laboratory evidence of SLE. The indication for biopsy was surveillance (60% of pts), worsening creatinine (Cr) (25%), proteinuria and worsening Cr (10%) and proteinuria (5%). At biopsy, 42% of pts had proteinuria which was > 1g/day in 21% of pts and mean Cr was 1.8 mg/dl. Only 11% of pts developed hematuria and none had hypoalbuminemia. One of the 3 pts whose native disease was FSGS had recurrent disease. The glomerular pattern on light microscopy was mesangial hypercellularity (45% of pts), FSGS (25%, including 1 of the 3 pts whose native disease was FSGS), and no lesions (30%). All cases showed intense (≥ 2+) dominant (65%) or co-dominant (35%) mesangial staining for C1q on immunofluorescence. Paramesangial electron dense deposits were seen in 14 of 17 (82%) biopsies studied ultrastructurally, but none showed subepithelial or subendothelial deposits or tubuloreticular inclusions. 5 pts were treated with pulse steroids for cellular rejection and 1 with plasmapheresis for recurrent FSGS. On follow-up (mean 20 mos), 35% of pts had stable Cr with no proteinuria, 12% had stable Cr with a reduction in proteinuria ≥50%, 29% had worsening Cr or <50% reduction in proteinuria, and 24% resumed HD or were re-transplanted (for causes other than C1qN).
Conclusions: C1qN in the renal allograft is a de novo disease in the majority of pts. It usually develops after the first year of transplant. Most cases are diagnosed as an incidental finding but some pts have mild proteinuria. Some cases may relate to infection. The most common histologic finding on light microscopy is mesangial hypercellularity.
Category: Kidney (does not include tumors)
Wednesday, March 24, 2010 1:00 PM
Poster Session VI # 230, Wednesday Afternoon