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IEMbase 0006: PCBD1-related pterin carbinolamine-4a-dehydratase deficiency

Scope

Field Value
IEMbase ID 6
Nosology 21.1.07.01
Gene PCBD1
External IDs OMIM:264070
Generated mapping UNMAPPED
Likely DisMech target kb/disorders/Tetrahydrobiopterin_Deficiency.yaml#PCD Deficiency
Review date 2026-07-07

IEMbase phenotype signal

IEMbase describes a relatively mild profile. Characteristic clinical entries are MODY3-like diabetes and transient alteration in tone; additional clinical coverage is limited to mild hypotonia.

The biochemical profile includes increased plasma phenylalanine, BH4 loading test response, abnormal pterin profile with primapterin in dried blood spot and urine, and glucose/magnesium abnormalities.

Treatments are protein-defined diet and sapropterin/BH4 cofactor therapy.

DisMech phenotype coverage

The generated crosswalk missed an existing subtype. Tetrahydrobiopterin Deficiency includes PCD Deficiency, describes PCBD1-related transient hyperphenylalaninemia with primapterinuria, and notes later MODY and hypomagnesemia risk.

The top-level DisMech phenotype list does not currently expose the PCD-specific clinical picture. It primarily covers the broader severe BH4 deficiency phenotype: neurodevelopmental delay, hypotonia, dystonia, parkinsonism, seizures, hyperphenylalaninemia, urinary pterin profile, and CSF neurotransmitter metabolites.

Concordance and completeness

Judgement: mapping false negative; local identity coverage exists but phenotype coverage is partial.

DisMech has the correct subtype concept and mechanism, but IEMbase highlights PCD-specific features that are not explicit as phenotype/biochemical records: MODY3-like diabetes, hypomagnesemia, primapterinuria, and the comparatively mild transient tone/hypotonia phenotype.

Curation actions

  • Add aliases or mapper normalization so the IEMbase PCBD1/PCD row maps to the PCD Deficiency subtype.
  • Consider subtype-specific phenotype/biochemical records for primapterinuria, hypomagnesemia, and MODY-like diabetes if supported by accepted sources.
  • Avoid importing the broad severe BH4 phenotype into PCD without subtype-level evidence.