Absence of thrombocytopaenia and/or microangiopathic haemolytic anaemia does not reliably exclude recurrence of atypical haemolytic uraemic syndrome after kidney transplantation

A 54-year-old man was diagnosed with atypical haemolytic uraemic syndrome (aHUS) with confirmed complement H mutation in 2012, requiring ongoing dialysis. He was commenced on eculizumab in 2014 once the pharmaceutical board approved this drug. After 4months, he received a live unrelated donor renal transplant from his wife and continued eculizumab post-transplant. Three months later, there was a rise in his creatinine with no laboratory features of haemolysis and a kidney biopsy confirmed rejection, which was treated with increased immunosuppression. After completing 12months of treatment with eculizumab, he opted for close monitoring rather than continuation with therapy. Five months post-cessation of the drug, there was a rise in creatinine, and once again, haematological parameters remained within reference range; however, his kidney biopsy showed features consistent with recurrence of aHUS; hence, eculizumab was recommenced with good effect. While there was no evidence of haemolysis, there was a gradual rise in LDH level and a drop in platelet count, although the parameters remained within the normal range. This suggests that aHUS can recur in the allograft in the absence of haematological abnormalities. Clinicians should have a low threshold for allograft biopsy if haematological parameters are not just outside the reference range, but possibly also if there are changes of at least >25% from baseline in platelet count and LDH levels, particularly in those patients who are no longer eligible for eculizumab.