IEMbase 0134: BCAT2-related Branched-chain aminotransferase 2 deficiency
Scope
| Field | Value |
|---|---|
| IEMbase ID | 134 |
| Nosology | 1.3.01.01 |
| Gene | BCAT2 |
| External IDs | OMIM:238340; OMIM:113530 |
| Generated mapping | UNMAPPED |
| Candidate DisMech targets | No valid BCAT2 target found; generated ornithine aminotransferase candidate is false |
| Review date | 2026-07-07 |
IEMbase phenotype signal
IEMbase represents this as BCAT2-related branched-chain aminotransferase 2 deficiency, with alternate labels hypervalinemia and hyperleucine-isoleucinemia, BCAA transaminase, and BCAT2. Treatability is marked unknown.
Characteristic biochemical rows include increased plasma isoleucine, leucine, and valine. Non-characteristic biochemical rows include normal allo-isoleucine, normal-to-increased arginine, normal-to-increased glycine, and normal total plasma acylcarnitines. Clinical rows include alopecia/loss of hair, hypotonia, ketoacidosis, metabolic acidosis, nystagmus, decreased spontaneous movement, hyperkinesia, failure to thrive, feeding difficulties, psychomotor delay, and episodic vomiting.
DisMech phenotype coverage
No standalone BCAT2 branched-chain aminotransferase deficiency target was found.
ornithine_aminotransferase_deficiency.yaml is a false lexical neighbor:
ornithine aminotransferase deficiency is an OAT retinal disorder with
hyperornithinemia, not a branched-chain amino-acid transamination disorder.
Maple_Syrup_Urine_Disease.yaml is a pathway neighbor because it models
branched-chain amino acid toxicity downstream of BCKD-complex deficiency and
mentions BCAT2-mediated transamination. It is not a valid disease target for
primary BCAT2 deficiency.
Concordance and completeness
Judgement: true unmapped local disease gap, with MSUD as context only.
The IEMbase record's elevated leucine, isoleucine, and valine profile overlaps with MSUD biochemistry, but the causal lesion is different. BCAT2 deficiency should not be collapsed into BCKD deficiency or OAT deficiency. Current DisMech does not provide a disease-level target for the BCAT2 entity.
Curation actions
- Keep this record unmapped.
- Do not map to ornithine aminotransferase deficiency.
- Treat MSUD as pathway context only; consider a future BCAT2 entry with BCAA elevations, ketoacidosis/metabolic acidosis, feeding/growth problems, psychomotor delay, hypotonia, and hair-loss/nystagmus signals.