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ORPHA:2102

GTP cyclohydrolase I deficiency

high confidenceSubtype of disorder

Also known as: GTPCH deficiency · Hyperphenylalaninemia due to GTP cyclohydrolase deficiency

Publications

117

57.5th percentile

Trials

1

Interventional, condition-specific

Researchers

655

Distinct authors in sample

Gene link

GCH1

Definitive

Readiness

3/6

Stages with a signal

Clinical definition (Orphanet)

GTP-cyclohydrolase I deficiency, an genetic disorder, is one of the causes of malignant hyperphenylalaninemia due to tetrahydrobiopterin deficiency. Not only does tetrahydrobiopterin deficiency cause hyperphenylalaninemia, it is also responsible for defective neurotransmission of monoamines because of malfunctioning tyrosine and tryptophan hydroxylases, both tetrahydrobiopterin-dependent hydroxylases.

How rare: <1 / 1 000 000 — fewer than one in a million. In a city the size of Kolkata, that might mean on the order of fifteen people.

Orphanet entry

Cross-references

Joined from Mondo / Orphanet. MeSH labels may enter searches; UMLS / OMIM / NCIT are stored for reference.

Additional Mondo synonyms (2)

hyperphenylalaninemia due to GTP cyclohydrolase deficiency · hyperphenylalaninemia, Bh4-deficient, type B

Research stages

Trial readiness signals

Where this condition sits on an open-data research pipeline — not how close a treatment is, and not medical advice. Empty stages often mean “not in these databases under this Mondo ID,” not “impossible.”

3/6 stages with a signal

An interventional trial matched this condition name on ClinicalTrials.gov — see trials below.

  1. Gene identifiedPresent

    Definitive — GCH1

  2. LiteraturePresent

    117 matched papers (61 in last 10 years) Source

  3. Phenotype characterisedNot checked

    Not yet enriched from Monarch / HPO

  4. Animal modelNot checked

    Not yet enriched from Monarch / Alliance

  5. Orphan designationNot checked

    FDA/EMA orphan-drug designation not enriched yet

  6. Interventional trialPresent

    1 matched on ClinicalTrials.gov

Biology

Genes and phenotypes

Gene–disease validity from GenCC, plus phenotypes and animal models joined from Monarch Initiative via Mondo ID — not a clinical diagnosis aid.

Do we know what causes it?

Yes — we know a specific gene responsible (GCH1).

GenCC classification: Definitive.

Phenotypes (Monarch / HPO)

Not enriched in this build — Monarch phenotype joins were not run for this record.

Animal models (Monarch / Alliance)

Not enriched in this build.

Literature

Is anyone studying this?

117

117 papers have ever been published on this condition (under this name). For scale, breast cancer has over 700,000. Median papers in the last 10 years for a rare disease in this dataset (publications denominator n=5449) is 41.

117 papers since the earliest indexed year in this search — median last-10-year count for a rare disease in this dataset is 41 (publications denominator n=5449).

61 in the last 10 years · high confidence · 57.5th percentile (publications denominator)

Phrase hits: 117 · MeSH hits: 0

Open Europe PMC search

Who's working on it?

655

Distinct author names in 117 sampled papers — named people below.

Who's working on it?

People publishing on this condition (sampled Europe PMC records). Affiliation is the most recent found in that sample.

  1. 01
    Blau N21 papers · 2026

    University Children's Hospital, Dietmar-Hoppe Metabolic Centre, Heidelberg, Germany.

    Papers in Europe PMC
  2. 02
    Opladen T9 papers · 2026

    Department of Child Neurology and Metabolic Disorders, University Children's Hospital, Heidelberg, Germany.

    Papers in Europe PMC
  3. 03
    Thöny B9 papers · 2021

    Division of Clinical Chemistry and Biochemistry, Laboratory of Molecular Genetic Investigation, University Children's Hospital Zürich, Zürich, Switzerland.

    Papers in Europe PMC
  4. 04
    Hoffmann GF7 papers · 2026

    Department of Pediatrics, University of Heidelberg, Heidelberg, Germany. georg_hoffmann@med.uni-heidelberg.de

    Papers in Europe PMC
  5. 05
    Nagatsu T7 papers · 2024

    Nagoya University Research Institute of Environmental Medicine, Nagoya, Japan . ; Fujita Health University School of Medicine, Toyoake, Aichi, Japan . ; Visiting Professor and Professor Emeritus.

    Papers in Europe PMC
  6. 06
    Burlina A5 papers · 2021

    Division of Inherited Metabolic Diseases, Department of Paediatrics, University Hospital of Padova, Padova, Italy.

    Papers in Europe PMC
  7. 07
    Niederwieser A5 papers · 1986
    Papers in Europe PMC
  8. 08
    Channon KM4 papers · 2017

    BHF Centre of Research Excellence, Division of Cardiovascular Medicine, Radcliffe Department of Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, United Kingdom. Electronic address: keith.channon@cardiov.ox.ac.uk.

    Papers in Europe PMC
  9. 09
    Crabtree MJ4 papers · 2017

    BHF Centre of Research Excellence, Division of Cardiovascular Medicine, Radcliffe Department of Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, United Kingdom.

    Papers in Europe PMC
  10. 10
    Leuzzi V4 papers · 2024

    Department of Paediatrics, Child Neurology and Psychiatry, Sapienza University of Rome, Via dei Sabelli 108, 00185, Rome, Italy.

    Papers in Europe PMC

Clinical research

Is a treatment being tested?

1

interventional trials for this specific condition

1 interventional trial matched this specific condition name; none in our sample are currently recruiting.

Data as of 27 July 2026

1 interventional trial — more than 73% of diseases in the trials denominator have none at all (5114 of 7003; this disease is at the 76.8th percentile).

high confidence · 76.8th percentile (trials denominator)

Recruiting interventional trials

From the matched ClinicalTrials.gov set

1 interventional trials matched after quoted-phrase search and title/condition post-filter.

No currently recruiting studies in the matched set. Open the same search on ClinicalTrials.gov.

Observational and natural-history studies

2 observational studies match this condition. These do not test a treatment and are not counted in the interventional-trial headline, but they are genuine research: natural-history work often defines the endpoints needed for a future rare-disease trial, and families may be able to enroll.

None of the matched observational studies is currently listed as recruiting.

Open the complete matched search on ClinicalTrials.gov

Where to find support

We do not yet link condition-specific patient organisations. These umbrella groups support undiagnosed and ultra-rare families:

India — NPRD

Last verified 2026-07-26

Likely covered — the policy lists Non-PKU hyperphenylalaninemia as a category (Group 2), and this condition is a form of it. Confirm eligibility with a Centre of Excellence.

Group 2 — long-term / lifelong lower-cost interventions

NPRD envisages State Government support for dietary formulae, hormones, and other lower-cost interventions. This is a different route from the central CoE ₹50 lakh pathway; ask your state health department and a CoE which channel applies.

Central CoE funding may also apply depending on current rules — confirm with a notified Centre of Excellence. Do not assume the ₹50 lakh ceiling covers Group 2 by default. Verify

Centres of Excellence (15)
  • All India Institute of Medical Sciences (AIIMS) — New Delhi, Delhi
  • Maulana Azad Medical College — New Delhi, Delhi
  • Sanjay Gandhi Post Graduate Institute of Medical Sciences — Lucknow, Uttar Pradesh
  • Post Graduate Institute of Medical Education and Research (PGIMER) — Chandigarh, Chandigarh
  • Centre for DNA Fingerprinting & Diagnostics with Nizam’s Institute of Medical Sciences — Hyderabad, Telangana
  • King Edward Memorial Hospital — Mumbai, Maharashtra
  • Institute of Post-Graduate Medical Education and Research (IPGMER) — Kolkata, West Bengal
  • Centre for Human Genetics with Indira Gandhi Hospital — Bengaluru, Karnataka
  • Institute of Child Health and Hospital for Children (ICH & HC) — Chennai, Tamil Nadu
  • All India Institute of Medical Sciences (AIIMS) — Jodhpur, Rajasthan
  • Sree Avittam Thirunal Hospital (SAT), Government Medical College — Thiruvananthapuram, Kerala
  • All India Institute of Medical Sciences (AIIMS) — Bhopal, Madhya Pradesh
  • Regional Institute of Medical Sciences (RIMS) — Imphal, Manipur
  • All India Institute of Medical Sciences (AIIMS) — Patna, Bihar
  • Assam Medical College & Hospital — Dibrugarh, Assam

Voluntary contributions / crowdfunding (separate from CoE funding): https://rarediseases.mohfw.gov.in/

Hand-curated for this project. ORPHAcode mappings are best-effort and may be incomplete or imprecise for umbrella categories. Parent (Mondo) matches mean the policy lists a broader category — confirm eligibility with a Centre of Excellence. Financial entitlements summarised from public policy statements and may change. This is not official government guidance.

How we counted this

Europe PMC query (preferred label + any corrected label + Orphanet and Mondo exact synonyms, stoplisted; unioned with resolved MeSH labels when available). UMLS / OMIM / NCIT cross-references are stored on the overview but are not added to the query string.

"GTP cyclohydrolase I deficiency" OR "GTPCH deficiency" OR "Hyperphenylalaninemia due to GTP cyclohydrolase deficiency" OR "hyperphenylalaninemia, Bh4-deficient, type B"

Run this search on Europe PMC

ClinicalTrials.gov query (quoted phrases + MeSH via query.cond, plus recall-expansion terms when used):

"GTP cyclohydrolase I deficiency" OR "GTPCH deficiency" OR "Hyperphenylalaninemia due to GTP cyclohydrolase deficiency" OR "hyperphenylalaninemia, Bh4-deficient, type B" OR "GCH1"

Recall-expansion terms: GCH1

Interventional trials matched via: phrase (mesh = registered under a MeSH descriptor no name phrase would catch; recall-expansion = gene / selected parent terms used only for trials).

Study-type breakdown: 1 interventional · 2 observational · 0 expanded access. Only interventional studies enter the trial headline.

Query health: ok — strategies attempted: phrase, recall-expansion; with hits: phrase, recall-expansion

Run this search on ClinicalTrials.gov

Confidence reasoning

  • Preferred label is multi-word and distinctive
  • No synonyms dropped by stoplist
  • No label/synonym collisions with other diseases in this corpus

Ingested 2026-07-26T19:06:54.198Z