Friedreich’s ataxia is a recessive genetic disorder that strikes in childhood or adolescence, progressively robbing patients of coordination, strength, and sensation. In roughly 96 percent of cases, it is caused by biallelic expansions of a GAA repeat sequence within the FXN gene, which silences production of frataxin, a protein essential to mitochondrial function in cells. The deficit cascades across multiple organ systems: the central and peripheral nervous systems degenerate, the heart muscle thickens into hypertrophic cardiomyopathy, the pancreas falters toward diabetes, and scoliosis, spasticity, and optic neuropathy often follow. Most therapeutic strategies now in development aim either to soften the downstream consequences of frataxin loss or to restore frataxin expression directly, through gene therapy delivered by adeno-associated viral vectors, protein replacement, or epigenetic reactivation of the damaged gene.

The idea that transplanted blood-forming cells might help the brain rests on an intriguing biological premise. Cells of the monocyte lineage can, under certain conditions, migrate into the central nervous system and potentially exchange material with resident brain cells, raising the possibility that donor-derived cells could act as delivery vehicles for frataxin to deficient tissue. The concept carries real appeal but also unresolved risks, and the mechanisms that would make it work have never been fully defined. The patient described in the new report, who underwent a complete stem cell replacement for reasons entirely unrelated to her ataxia, offered a natural test of whether such replacement could alter the disease course.

Her medical odyssey began at age ten, when chest pain and a racing heartbeat landed her in the intensive care unit with thyrotoxicosis. During that hospitalization, doctors noted persistent cytopenias, and a bone marrow aspirate revealed acute myeloid leukemia carrying the t(6;9) translocation, a high-risk subtype with a strong tendency to relapse. At the same time, subtle neurological signs emerged: a slightly wide-based gait with externally rotated legs, ataxia, faint tremors confined to her fingers, diminished vibratory sensation, and absent deep tendon reflexes. Genetic testing confirmed biallelic GAA expansions in FXN of 699 and 1066 repeats, establishing the diagnosis of Friedreich’s ataxia, and an echocardiogram revealed moderate left ventricular hypertrophy, the disease’s characteristic cardiac signature.

Treating the leukemia in a child with a fragile heart demanded a delicate balancing act. Induction chemotherapy with a dose-adjusted regimen of cytarabine, daunorubicin, and etoposide failed to achieve remission, forcing a switch to a salvage combination of topotecan, vinorelbine, thiotepa, and clofarabine, which succeeded in driving the leukemia to minimal residual disease negativity after two cycles. She then received an allogeneic hematopoietic stem cell transplant from an 11-of-12 HLA-matched unrelated male donor, using CD34-positive selected peripheral blood stem cells. Her conditioning regimen combined rabbit anti-thymocyte globulin, clofarabine, melphalan, and thiotepa. Remarkably, the procedure proceeded without major unexpected complications, no graft-versus-host disease developed, and she has remained in leukemia remission for the entire decade since.

The neurological story, however, unfolded exactly as it would have without the transplant. Over ten years, her speech became mildly affected, her gait and arm function worsened, and her reflexes and peripheral neuropathic components showed no reversal. Quantitative measures told the same story: her modified Friedreich Ataxia Rating Scale score climbed by 20 points, and her nine-hole peg test times doubled, tracking the trajectory of six comparator patients at the same institution who had similar GAA repeat lengths and ages of onset but received no transplant. She now uses a wheelchair and cannot ambulate independently, and she developed diabetes and sleep apnea along the way. In short, a fully successful bone marrow replacement did nothing to touch the degeneration in her nervous system.

The authors of the report point to several converging reasons why. The blood-brain barrier excludes most donor-derived cells from entering the brain’s parenchyma, and conventional stem cell transplantation does not achieve the deep microglial and monocyte depletion that some researchers believe would be necessary for donor cells to meaningfully repopulate the central nervous system. Frataxin itself is an intracellular mitochondrial protein, which means donor cells cannot perform the kind of cross-correction seen in some other metabolic storage diseases, where secreted enzymes rescue neighboring cells. Friedreich’s ataxia also carries significant developmental components, so replacing frataxin after the developmental window may simply come too late to rescue already-compromised neural circuits. Finally, the chemotherapy required to conquer her leukemia may itself have aggravated her neuropathy, and her secondary diabetes could have blunted any residual benefit.

Yet the case contains one genuinely striking observation. While her neurological scores marched steadily downward, her cardiac hypertrophy stabilized. Ten years after the transplant, her echocardiogram was read as normal, and comparisons of her ejection fraction and intraventricular septal diameter against the six matched comparator patients suggested her heart measures had held steady where others continued to change. The authors urge caution in interpreting this, noting that wall thickness in Friedreich’s ataxia is only modestly predictive of long-term outcome, that reductions in wall thickness can occur without lasting benefit, and that some comparator subjects showed similar stabilization. Ejection fraction changes are typically late phenomena in the disease, so a decade of stability is notable but not definitive proof of cardiac protection.

The clearest confirmation of the transplant’s biological success came from her blood. Genetic testing performed ten years after the procedure showed GAA repeat lengths of 10 and 16, entirely normal values reflecting the donor’s healthy genome, and her blood frataxin levels had returned to the control range, measured at 4.79 nanograms per milliliter for the mature form and 9.25 for the extended form. Her hematopoietic system had been completely rebuilt from genetically unaffected donor cells, demonstrating that full donor chimerism and normalized frataxin production in blood are achievable in a Friedreich’s ataxia patient, even if the nervous system remained beyond reach.

Because Friedreich’s ataxia is not known to elevate cancer risk, the co-occurrence of leukemia in this patient was almost certainly coincidental, but it dramatically complicated her treatment, given the cardiac sensitivity and neurotoxicity risks posed by many chemotherapy agents. The successful outcome nonetheless establishes that Friedreich’s ataxia patients can survive allogeneic stem cell transplantation, just as they have survived heart and liver transplantation in prior reports, opening a door for treating hematologic malignancies in this population. And the hint of cardiac stabilization, combined with the procedure’s relative safety, keeps alive the possibility that stem cell approaches could one day benefit the disease, if deployed in paradigms specifically engineered to deliver frataxin to the central nervous system. The authors are careful to stress that the present observations cannot be taken as evidence of neurological benefit, but the case stands as a rare, decade-long natural experiment that maps both the promise and the hard biological limits of replacing a patient’s blood to heal a brain.

Subject of Research: Allogeneic stem cell transplantation in a patient with Friedreich's ataxia and acute myeloid leukemia

Article Title: Stem Cell Transplantation in Friedreich Ataxia: Cure for Leukemia but No Effect on Neurological Progression

Article References: Gitman, A., Bhandari, N., Castellaro, M., Schadt, K., Cancio, M., & Lynch, D. R. (2026). Stem Cell Transplantation in Friedreich Ataxia: Cure for Leukemia but No Effect on Neurological Progression. Annals of Clinical and Translational Neurology, 13(8), 1733-1735. https://doi.org/10.1002/acn3.70455

Image Credits: AI Generated

DOI: 10.1002/acn3.70455

Keywords: Friedreich's ataxia, stem cell transplantation, frataxin, acute myeloid leukemia, FXN gene, neurodegeneration, cardiomyopathy, blood-brain barrier, gene therapy, GAA repeat expansion, hematopoietic stem cells, case report