Transcobalamin (TC) deficiency—Potential cause of bone marrow failure in childhood
Bibliographic record
Abstract
It is unusual for inborn errors of metabolism to be considered in the investigative work-up of pancytopenia. We report a family in which the proband presented with failure to thrive at 2 months of age and subsequent bone marrow failure. A previous sibling had died at 7 months of age with suspected leukaemia. Haematological findings in the proband were significant for pancytopenia, and bone marrow aspiration showed dysplastic changes in all cell lineages. Urinary organic acid analysis revealed elevated methylmalonic acid. The synthesis of transcobalamin II (transcobalamin, TC) by cultured fibroblasts was markedly reduced, confirming the diagnosis of TC deficiency. The proband and his younger asymptomatic sister (also found to have TC deficiency) were homozygous for R399X (c.1195C>T), a novel mutation resulting in the loss of the C- terminal 29 amino acids of TC, a highly conserved region. Response to parenteral vitamin B(12) in the proband was dramatic. At 6 years 3 months of age, physical examination is normal and developmental level is age appropriate. His sister is clinically asymptomatic and is also developing normally. Propionylcarnitine concentrations were not elevated in the newborn screening cards from the proband and sister, but that was for specimens retrieved from storage after 7 years and 5 years, respectively. Inherited and acquired cobalamin disorders should both be considered in the differential diagnosis of bone marrow failure syndromes in young children. Early detection of the metabolic causes of bone marrow failure can ensure prompt recovery in some cases involving the vitamin B(12) pathway.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".