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Spontaneous improvement of carbohydrate-deficient transferrin in PMM2-CDG without mannose observed in CDG natural history study

  • Witters, Peter1, 2
  • Edmondson, Andrew C.3
  • Lam, Christina4, 5
  • Johnsen, Christin6
  • Patterson, Marc C.7
  • Raymond, Kimiyo M.7
  • He, Miao3
  • Freeze, Hudson H.8
  • Morava, Eva6
  • 1 University Hospitals Leuven, Herestraat 49, Leuven, 3000, Belgium , Leuven (Belgium)
  • 2 KU Leuven, Leuven, Belgium , Leuven (Belgium)
  • 3 Children’s Hospital of Philadelphia, Philadelphia, PA, USA , Philadelphia (United States)
  • 4 University of Washington, Seattle, WA, USA , Seattle (United States)
  • 5 Seattle Children’s Research Institute, Seattle, WA, USA , Seattle (United States)
  • 6 Mayo Clinic, 200 First Street, SW, Rochester, MN, 55905, USA , Rochester (United States)
  • 7 Mayo Clinic, Rochester, MN, USA , Rochester (United States)
  • 8 Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA , La Jolla (United States)
Published Article
Orphanet Journal of Rare Diseases
Springer (Biomed Central Ltd.)
Publication Date
Feb 25, 2021
DOI: 10.1186/s13023-021-01751-2
Springer Nature


A recent report on long-term dietary mannose supplementation in phosphomannomutase 2 deficiency (PMM2-CDG) claimed improved glycosylation and called for double-blind randomized study of the dietary supplement in PMM2-CDG patients. A lack of efficacy of short-term mannose supplementation in multiple prior reports challenge this study’s conclusions. Additionally, some CDG types have previously been reported to demonstrate spontaneous improvement in glycosylated biomarkers, including transferrin. We have likewise observed improvements in transferrin glycosylation without mannose supplementation. This observation questions the reliability of transferrin as a therapeutic outcome measure in clinical trials for PMM2-CDG. We are concerned that renewed focus on mannose therapy in PMM2-CDG will detract from clinical trials of more promising therapies. Approaches to increase efficiency of clinical trials and ultimately improve patients’ lives requires prospective natural history studies and identification of reliable biomarkers linked to clinical outcomes in CDG. Collaborations with patients and families are essential to identifying meaningful study outcomes.

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