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Isolated arterial mucoid intimal thickening lesion in early post-transplant kidney allograft biopsies
Mineaki Kitamura1,2, Mohan Doraiswamy3, Bryce Parkinson1
1Department of Pathology, Division of Renal and Transplant Pathology, The Ohio State University Wexner Medical Center, Columbus, Ohio, US.
Introduction:
Thrombotic microangiopathy (TMA) on kidney biopsy shows a variable combination of features: arterial mucoid intimal thickening, acellular closure of glomerular capillary loops, fragmented red blood cells, fibrin thrombi, and arterial fibrinoid necrosis. However, some early post-transplant kidney biopsies show only arterial mucoid intimal thickening. We aimed to elucidate the importance of this finding.
Methods:
We identified 19 biopsies showing isolated arterial mucoid intimal thickening and compared them with 22 bona fide TMA biopsies identified based on the pathological findings (excluding rejection) (2011-2020). Additionally, delayed graft function (DGF) (n = 237), and no DGF (control, n = 1314) groups were included for survival analysis.
Results:
Seven of 19 cases with isolated arterial mucoid intimal thickening showed peripheral blood schistocytes but no other systemic features of TMA. Eight patients underwent adjustments in maintenance immunosuppression (mainly calcineurin inhibitors). None of the cases progressed to full-blown TMA on consecutive biopsies. The overall and death-censored graft survival rates in this group were comparable to the DGF group, but significantly better than the TMA group (P = .005 and .04, respectively).
Conclusions:
Isolated arterial mucoid intimal thickening in early post-transplant biopsies may be an early/mild form of TMA, probably requiring adjustment in immunosuppressive regimen. Careful exclusion of known causes of TMA, and donor-derived arterial injury are important.
Insights
Isolated arterial mucoid intimal thickening in kidney transplants may indicate early thrombotic microangiopathy (TMA). Prompt immunosuppression adjustments can improve outcomes, showing better graft survival than established TMA.
Area of Science:
- Nephrology
- Transplant Pathology
- Immunosuppression
Background:
- Thrombotic microangiopathy (TMA) presents with diverse kidney biopsy findings.
- Early post-transplant biopsies may exhibit isolated arterial mucoid intimal thickening, a finding whose significance is unclear.
Purpose of the Study:
- To determine the clinical importance of isolated arterial mucoid intimal thickening in early kidney allograft biopsies.
- To assess the association of this finding with thrombotic microangiopathy (TMA) and patient outcomes.
Main Methods:
- Retrospective analysis of 19 kidney biopsies with isolated arterial mucoid intimal thickening.
- Comparison with 22 biopsies of confirmed TMA and survival analysis against delayed graft function (DGF) and no-DGF control groups.
Main Results:
- Seven cases showed peripheral schistocytes, but no other systemic TMA features.
- Eight patients had immunosuppression adjustments; none progressed to full TMA.
- Graft survival in the isolated thickening group was comparable to DGF and superior to TMA groups.
Conclusions:
- Isolated arterial mucoid intimal thickening may represent an early or mild form of TMA.
- Immunosuppression adjustment may be warranted.
- Excluding other TMA causes and considering donor factors are crucial.
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