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Background <p>Ideally, deceased donor kidney transplantation is preferred for patients with mitochondrial nephropathy caused by the m.3243&#xa0;A &gt; G mutation to avoid genetic risks. However, in regions where deceased donation is limited and living donation predominates, such as Japan, family members are often the only available donors. The safety of using maternal relatives, who are obligate carriers of the mutation, remains highly controversial due to the risk of unmasking renal failure in both the donor and the allograft.</p> Case presentation <p>We report a 22-year follow-up of an inadvertent living kidney transplant from a 55-year-old mother to her 26-year-old daughter. The recipient presented with MELAS (Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Stroke-like episodes) and end-stage kidney disease due to focal segmental glomerulosclerosis (FSGS), with the m.3243&#xa0;A &gt; G mutation confirmed prior to transplantation. Conversely, the donor mother was phenotypically normal regarding renal function without diabetes, and conventional genetic testing at the time failed to detect the mutation. Consequently, the recipient’s mutation was presumed to be de novo, allowing the donation to proceed. Notably, the donor’s zero-hour allograft biopsy revealed ultrastructural mitochondrial abnormalities but no overt light microscopic damage (i.e., no FSGS). At 22 years post-transplant, both the recipient’s graft function (serum creatinine 1.16&#xa0;mg/dL, albuminuria 5.0&#xa0;mg/gCr) and the donor’s remaining kidney function (serum creatinine 0.98&#xa0;mg/dL, albuminuria 10.4&#xa0;mg/gCr) remain excellent. Current highly sensitive genetic analysis revealed an extremely low blood heteroplasmy in the donor (0.1%) compared to 20% in the recipient, demonstrating a severe “genetic bottleneck” effect. Furthermore, the recipient’s older sister was found to have a 4% mutational load, definitively confirming maternal inheritance rather than a de novo mutation.</p> Conclusions <p>This case represents the longest reported follow-up of a living kidney transplant from an m.3243&#xa0;A &gt; G carrier. It demonstrates that maternal carriers with extremely low heteroplasmy and no light microscopic evidence of overt renal damage on biopsy can be safe donors and provide excellent long-term graft outcomes. Precise risk stratification based on genotype and biopsy findings, rather than uniform exclusion, may expand transplant options.</p>

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Long-term donor and graft safety despite subclinical mitochondrial abnormalities: mechanistic insights from a 22-year follow-up of a carrier-to-MELAS kidney transplant

  • 期刊论文

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  • 发表日期：

    2026年7月28日

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  • Shizuka Kobayashi,
  • Tomokazu Shimizu,
  • Shun Manabe,
  • Momoko Seki,
  • Yusuke Ushio,
  • Rina Takahashi,
  • Shiho Makabe,
  • Naoko Ito,
  • Kohei Unagami,
  • Hiroshi Kataoka,
  • Sekiko Taneda,
  • Toshihiro Hirai,
  • Kazuho Honda,
  • Kosaku Nitta,
  • Toshio Takagi,
  • Hideki Ishida,
  • Junichi Hoshino

摘要

Background

Ideally, deceased donor kidney transplantation is preferred for patients with mitochondrial nephropathy caused by the m.3243 A > G mutation to avoid genetic risks. However, in regions where deceased donation is limited and living donation predominates, such as Japan, family members are often the only available donors. The safety of using maternal relatives, who are obligate carriers of the mutation, remains highly controversial due to the risk of unmasking renal failure in both the donor and the allograft.

Case presentation

We report a 22-year follow-up of an inadvertent living kidney transplant from a 55-year-old mother to her 26-year-old daughter. The recipient presented with MELAS (Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Stroke-like episodes) and end-stage kidney disease due to focal segmental glomerulosclerosis (FSGS), with the m.3243 A > G mutation confirmed prior to transplantation. Conversely, the donor mother was phenotypically normal regarding renal function without diabetes, and conventional genetic testing at the time failed to detect the mutation. Consequently, the recipient’s mutation was presumed to be de novo, allowing the donation to proceed. Notably, the donor’s zero-hour allograft biopsy revealed ultrastructural mitochondrial abnormalities but no overt light microscopic damage (i.e., no FSGS). At 22 years post-transplant, both the recipient’s graft function (serum creatinine 1.16 mg/dL, albuminuria 5.0 mg/gCr) and the donor’s remaining kidney function (serum creatinine 0.98 mg/dL, albuminuria 10.4 mg/gCr) remain excellent. Current highly sensitive genetic analysis revealed an extremely low blood heteroplasmy in the donor (0.1%) compared to 20% in the recipient, demonstrating a severe “genetic bottleneck” effect. Furthermore, the recipient’s older sister was found to have a 4% mutational load, definitively confirming maternal inheritance rather than a de novo mutation.

Conclusions

This case represents the longest reported follow-up of a living kidney transplant from an m.3243 A > G carrier. It demonstrates that maternal carriers with extremely low heteroplasmy and no light microscopic evidence of overt renal damage on biopsy can be safe donors and provide excellent long-term graft outcomes. Precise risk stratification based on genotype and biopsy findings, rather than uniform exclusion, may expand transplant options.