Early relapse of atypical hemolytic uremic syndrome following ABO-incompatible living-related pediatric kidney re-transplant successfully treated with eculizumab

TMA in Kidney Transplantation

Thrombotic microangiopathy (TMA) is a rare and devastating complication of kidney transplantation, which often leads to graft failure. Posttransplant TMA (PT-TMA) may occur either de novo or as a recurrence of the disease. De novo TMA can be triggered by immunosuppressant drugs, antibody-mediated rejection, viral infections, and ischemia/reperfusion injury in patients with no evidence of the disease before transplantation. Recurrent TMA may occur in the kidney grafts of patients with a history of atypical hemolytic uremic syndrome (aHUS) in the native kidneys. Studies have shown that some patients with aHUS carry genetic abnormalities that affect genes that code for complement regulators (CFH, MCP, CFI) and components (C3 and CFB), whereas in 10% of patients (mostly children), anti-FH autoantibodies have been reported. The incidence of aHUS recurrence is determined by the underlying genetic or acquired complement abnormality. Although treatment of the causative agents is usually the first line of treatment for de novo PT-TMA, this approach might be insufficient. Plasma exchange typically resolves hematologic abnormalities but does not improve kidney function. Targeted complement inhibition is an effective treatment for recurrent TMA and may be effective in de novo PT-TMA as well, but it is necessary to establish which patients can benefit from different therapeutic options and when and how these can be applied.

ABO Incompatible Kidney Transplant in a Patient With Atypical Hemolytic Uremic Syndrome: Case Report

Kidney transplant (KT) or renal transplant is 1 of the preferred treatment options for patients with end-stage renal disease, but the presence of atypical hemolytic uremic syndrome (aHUS) further increases the risk of reoccurrence with graft rejection, and poor outcomes. ABO incompatibility further adds to the rejection risk. Here, we present a case of a young adult with a history of aHUS undergoing a successful ABO-incompatible (ABOi) renal transplant. ABO incompatibility desensitization was carried out, and the antibody titer was reduced to nullify the risk of rejection. Graft acceptance was facilitated by triple immunosuppression (steroid, tacrolimus, and mycophenolate mofetil), and 4-month serum creatinine follow-up indicated the absence of antibody-mediated rejection and recurrence of aHUS. This case demonstrates that in patients with aHUS, ABOi renal transplant can be performed successfully.

Pediatric Atypical Hemolytic Uremic Syndrome Advances

Atypical hemolytic uremic syndrome (aHUS) is a rare disorder characterized by dysregulation of the alternate pathway. The diagnosis of aHUS is one of exclusion, which complicates its early detection and corresponding intervention to mitigate its high rate of mortality and associated morbidity. Heterozygous mutations in complement regulatory proteins linked to aHUS are not always phenotypically active, and may require a particular trigger for the disease to manifest. This list of triggers continues to expand as more data is aggregated, particularly centered around COVID-19 and pediatric vaccinations. Novel genetic mutations continue to be identified though advancements in technology as well as greater access to cohorts of interest, as in diacylglycerol kinase epsilon (DGKE). DGKE mutations associated with aHUS are the first non-complement regulatory proteins associated with the disease, drastically changing the established framework. Additional markers that are less understood, but continue to be acknowledged, include the unique autoantibodies to complement factor H and complement factor I which are pathogenic drivers in aHUS. Interventional therapeutics have undergone the most advancements, as pharmacokinetic and pharmacodynamic properties are modified as needed in addition to their as biosimilar counterparts. As data continues to be gathered in this field, future advancements will optimally decrease the mortality and morbidity of this disease in children.