Diagnosis of de novo localized thrombotic microangiopathy by surveillance biopsy

Drug-induced de novo thrombotic microangiopathy diagnosed 2 years after renal transplantation: a case report and literature review

Background

Post-transplant de novo thrombotic microangiopathy (TMA) is a rare yet serious complication that generally can develop in renal transplant recipients immediately after reperfusion or several months after transplantation. Here, we report a case of systemic tacrolimus-associated TMA in a patient diagnosed 2 years after renal transplantation.

Case presentation

A 49-year-old woman presented with severe anemia 18 months after undergoing renal transplantation. Anemia was refractory to recombinant human erythropoietin and was suspected to be due to excessive menstruation. Anemia persisted even after hysterectomy, and thereafter, pancytopenia developed. A bone marrow biopsy was performed and showed no evidence of myeloproliferative neoplasms. Furthermore, an increase in serum lactate dehydrogenase level and the appearance of schistocytes on peripheral blood smear was noted 24 months post-transplant. Other possible causes of de novo TMA were excluded, and an allograft biopsy was performed. Pathological findings of the allograft biopsy showed that some afferent arterioles had formed thrombi. Suspecting tacrolimus to be the cause of TMA, 25 months after the transplant, we switched treatment to cyclosporine. Pancytopenia and renal function improved after switching to this calcineurin inhibitor. Subsequently, her allograft renal function stabilized for three years after renal transplantation.

Conclusion

We encountered a case of secondary drug-induced TMA in the late stages of renal transplantation. Therefore, TMA should be suspected when anemia with hemolysis is observed in recipients of kidney transplant.

A non-invasive laboratory panel as a diagnostic and prognostic biomarker for thrombotic microangiopathy: development and application in a Chinese cohort study

Background

Thrombotic microangiopathy (TMA) in the kidney is a histopathologic lesion that occurs in a number of clinical settings and is often associated with poor renal prognosis. The standard test for the diagnosis of TMA is the renal biopsy; noninvasive parameters such as potential biomarkers have not been developed.

Methods

We analyzed routine parameters in a cohort of 220 patients with suspected TMA and developed a diagnostic laboratory panel by logistic regression. The levels of candidate markers were validated using an independent cohort (n = 46), a cohort of systemic lupus erythematosus (SLE) (n = 157) and an expanded cohort (n = 113), as well as 9 patients with repeat biopsies.

Results

Of the 220 patients in the derivation cohort, 51 patients with biopsy-proven TMA presented with a worse renal prognosis than those with no TMA (P = 0.002). Platelet and L-lactate dehydrogenase (LDH) levels showed an acceptable diagnostic value of TMA (AUC = 0.739 and 0.756, respectively). A panel of 4 variables - creatinine, platelets, ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats 13) activity and LDH - can effectively discriminate patients with TMA (AUC = 0.800). In the validation cohort, the platelet and LDH levels and the 4-variable panel signature robustly distinguished patients with TMA. The discrimination effects of these three markers were confirmed in patients with SLE. Moreover, LDH levels and the 4-variable panel signature also showed discrimination values in an expanded set. Among patients undergoing repeat biopsy, increased LDH levels and panel signatures were associated with TMA status when paired evaluations were performed. Importantly, only the 4-variable panel was an independent prognostic marker for renal outcome (hazard ratio = 3.549; P<0.001).

Conclusions

The noninvasive laboratory diagnostic panel is better for the early detection and prognosis of TMA compared with a single parameter, and may provide a promising biomarker for clinical application.