Alport syndrome (AS) patients in Japan undergoing a kidney transplant were found to have long-term survival rates similar to patients whose transplant was due to other causes of kidney failure, a study in that country reports.
The study, “Long-term survival in Japanese renal transplant recipients with Alport syndrome: a retrospective study,” was published in the journal BMC Nephrology.
Alport syndrome is caused by defects in a major structural protein called type 4 collagen, which is essential for the normal functioning of the kidney, inner ear, and eye.
In the kidney, this protein is a key component of the glomerular basement membrane (GBM) of the glomeruli, small structures responsible for filtering the blood and producing urine. Defects in type 4 collagen allow the passage of blood and protein into the urine and lead to progressive scarring of the kidney, which can lead to kidney disease and organ failure.
A kidney transplant is currently the only available way of restoring kidney function in Alport patients. Previous studies conducted in several countries — such as Ireland, Australia, New Zealand, and Turkey — have shown that post-transplant survival rates for these patients match or even exceed those of patients with end-stage kidney disease from other causes.
It is also believed that Alport patients undergoing a transplant do not have disease recurrence in the kidney. However, several studies have suggested that the defective type 4 collagen in the glomeruli is produced by bone marrow-derived cells that travel to the kidney, highlighting the possibility of recurrence of Alport syndrome.
A small percentage (1.9%) of Alport patients may also develop a rare post-transplant complication called anti-GBM disease, which is caused by an abnormal production of antibodies against the GBM, leading to graft failure.
Researchers in Japan evaluated and compared, for the first time, the clinical outcomes of a kidney transplant in Japanese patients with or without Alport syndrome, and investigated the potential for disease recurrence and anti-GBM disease in these Alport patients.
They retrospectively analyzed the clinical and laboratory data of 21 Alport patients and 41 closely-matched patients without Alport syndrome (control group), who underwent a kidney transplant between February 1984 and February 2015 at either of two Japanese hospitals.
The mean age of Alport patients was 22 and 23 for non-Alport patients; all were followed-up for a median of 99.5 months (more than 8 years).
Most (about 90%) of these patients received a kidney from a living relative, and the others received the organ from a deceased donor.
Results showed no significant differences in patient and graft survival between people with or without Alport syndrome after a kidney transplant. The 10-year post-transplant survival rate was 100% in the Alport group and 94.6% in the control group, and 10-year graft survival was 69.3% among Alport patients and 64.2% among those in the control group.
Six Alport patients (28.6%) and 19 patients (46.3%) with other causes of end-stage kidney disease developed graft loss. In both groups, graft failure was mainly caused by chronic rejection, followed by non-compliance with medication. No case of anti-GBM disease was detected.
Outcomes in this sample of the Japanese population support previous studies finding equivalent patient and graft survival rates after kidney transplant between people with or without Alport syndrome.
A detailed analysis of the graft tissue in six of the 21 Alport patients more than one year after their transplant detected no signs of disease recurrence and showed that the GBM remained normal throughout time. This suggested that disease recurrence “was not present or was very limited in recipients with AS [Alport syndrome],” the researchers wrote.
However, the team noted that two patients showed a focally thin GBM, which suggested a potential transmission of thin basement membrane disease — a milder version of Alport syndrome caused by mutations that also affect type 4 collagen — from affected related donors.
They highlighted that these findings also support previous studies recommending a careful evaluation of potential donors, particularly for mutations in key Alport genes.
Additional studies with longer follow-ups to evaluate “the possible recurrence of AS and transmission of thin basement membrane disease from affected relatives will contribute to a better understanding of kidney transplantation in patients with AS,” the researchers concluded.
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