Document Type : case report


1 Pediatric Endocrinology Department, Akbar Hospital, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran

2 Molecular and Clinical Sciences Institute, St. George’s, University of London, Cranmer Terrace, London SW17 0RE, UK


Transcobalamin deficiency as a rare autosomal recessive disorder and methylmalonic acidemia is an autosomal recessive disorder of amino acid metabolism. Based on the common presentation of methylmalonic academia and Transcobalamin deficiency, in this case report, we presented rare cases of Transcobalamin deficiency in children with the primary diagnosis of methylmalonic academia. As the genetic test indicated the definite diagnosis, we fortunately treated our patient based on the genetic result to solve B12 deficiency and it showed promising outcomes.


  1. Xu S, Xiao Z, Yu S, Zeng W, Zhu Y, Zhou J. Enhanced cobalamin biosynthesis in Ensifer adhaerens by regulation of key genes with gradient promoters. Synthetic and Systems Biotechnology. 2022 Sep 1; 7(3):941-8.
  2. Guéant JL, Guéant-Rodriguez RM, Kosgei VJ, Coelho D. Causes and consequences of impaired methionine synthase activity in acquired and inherited disorders of vitamin B12 metabolism. Critical Reviews in Biochemistry and Molecular Biology. 2022 Mar 4; 57(2):133-55.
  3. Wright E. Newborn Screening for Inherited Metabolic Diseases. InNutrition Management of Inherited Metabolic Diseases: Lessons from Metabolic University 2022 Jun 15 (pp. 23-32). Cham: Springer International Publishing.
  4. Alam MM, Alathaibi A, Matloob R, Oshi MA. Transcobalamin II Deficiency Can Present without Hematological Manifestations: A Novel TCN2 Gene Variant. Asian Hematology Research Journal. 2022 Aug 12; 6(3):25-9.
  5. Venturoni LE, Venditti CP. Treatment of metabolic disorders using genomic technologies: Lessons from methylmalonic acidemia. Journal of Inherited Metabolic Disease. 2022 Sep; 45(5):872-88.
  6. Abuyaman O, Hatmal MM, Hijjawi N, Deeb AA, Abuothman M, Taha M. Vitamin B12 binding to mutated human transcobalamin, in-silico study of TCN2 alanine scanning and ClinVar missense mutations/SNPs. Journal of Biomolecular Structure and Dynamics. 2022 Feb 28:1-2.
  7. Pappas KB, Younan M, Conway R. Transcobalamin receptor deficiency in seven asymptomatic patients ascertained through newborn screening. American Journal of Medical Genetics Part A. 2022 Apr; 188(4):1102-8.
  8. O'Logbon J, Crook M, Steed D, Harrington DJ, Sobczyńska-Malefora A. Ethnicity influences total serum vitamin B12 concentration: a study of Black, Asian and White patients in a primary care setting. Journal of Clinical Pathology. 2022 Sep 1; 75(9):598-604.
  9. Wiedemann A, Oussalah A, Lamireau N, Theron M, Julien M, Mergnac JP, Augay B, Deniaud P, Alix T, Frayssinoux M, Feillet F. Clinical, phenotypic and genetic landscape of case reports with genetically proven inherited disorders of vitamin B12 metabolism: A meta-analysis. Cell Reports Medicine. 2022 Jul 19; 3(7):100670.
  10. Alamri A, AlMutairi Z, AlQahtani I, Sharaf FA, AlJabri H. Early Recognition and Treatment of TC II Deficiency: Case Report. International Journal of Health Sciences. 2022 Apr (III):3984-90.
  11. Gerrard A, Dawson C. Homocystinuria diagnosis and management: it is not all classical. Journal of Clinical Pathology. 2022 Nov 1; 75(11):744-50.