IEMbase 0092: CD320-related transcobalamin receptor defect
Scope
| Field | Value |
|---|---|
| IEMbase ID | 92 |
| Nosology | 21.9.06.01 |
| Gene | CD320 |
| External IDs | OMIM:613646 |
| Generated mapping | UNMAPPED; best fuzzy candidate Methylmalonic_Acidemia.yaml |
| Candidate DisMech targets | No exact local target |
| Review date | 2026-07-07 |
IEMbase phenotype signal
IEMbase represents this as autosomal recessive CD320-related transcobalamin receptor defect, with alternate labels TCR/CD320 defect, TCR, and methylmalonic acidemia TCblR type. Treatability is marked unknown, although hydroxocobalamin is listed as a treatment row.
The characteristic clinical row is "No consistent clinical picture".
The biochemical signal is narrow: characteristic urinary methylmalonic acid, with total plasma homocysteine also represented in the biochemical panel.
DisMech phenotype coverage
There is no exact DisMech disease entry or subtype for CD320/transcobalamin receptor deficiency.
Methylmalonic_Acidemia.yaml is a false-positive fuzzy candidate. It covers
isolated methylmalonic acidemia caused by MMUT and adenosylcobalamin-handling
defects such as MMAA and MMAB, but it does not model CD320-mediated cellular
uptake of transcobalamin-bound cobalamin.
Inborn_Disorder_of_Cobalamin_Metabolism_and_Transport.yaml is mechanistically
nearer because it includes cellular uptake and transport defects, but its
subtypes list TCN2, LMBRD1, ABCD4, and intracellular cobalamin groups rather
than CD320.
Concordance and completeness
Judgement: no valid local disease-level target.
The local cobalamin umbrella has the right broad mechanism class, but it lacks the CD320 receptor subtype. Mapping this record to isolated MMA would obscure the upstream cobalamin uptake lesion and the IEMbase statement that there is no consistent clinical picture.
Curation actions
- Do not map this record to
Methylmalonic_Acidemia.yaml. - Consider a CD320/transcobalamin receptor defect entry or a CD320 subtype under the cobalamin metabolism and transport umbrella if disease-entry scope is accepted.
- If curated, capture the narrow biochemical signal separately from isolated MMUT/MMAA/MMAB methylmalonic acidemia.