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ORPHA:247525

Citrullinemia type I

high confidenceDisorder

Also known as: ASS deficiency · Argininosuccinate synthase deficiency · Argininosuccinate synthetase deficiency · Argininosuccinic acid synthase deficiency · Argininosuccinic acid synthetase deficiency · CTLN1 · Citrullinemia type 1 · Classic citrullinemia

Query health: suspect — Only one of 2 strategies returned hits (phrase).

Publications

647

89th percentile

Trials

1

Interventional, condition-specific

Researchers

1,419

Distinct authors in sample

Gene link

ASS1

Definitive

Readiness

3/6

Stages with a signal

Clinical definition (Orphanet)

Citrullinemia type I is a rare urea cycle defect characterized biologically by and clinically by lethargy, poor feeding and vomiting in the form (Acute citrullinemia type I) and by variable in the later-onset form (Adult-onset citrullinemia type I).

How rare: 1-9 / 100 000 — about one to nine people per hundred thousand.

Orphanet entry

Cross-references

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

Additional Mondo synonyms (7)

argininosuccinate synthase deficiency · argininosuccinate synthetase deficiency · argininosuccinic acid synthase deficiency · argininosuccinic acid synthetase deficiency · citrullinemia type 1 · citrullinemia type I · classic citrullinemia

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 — ASS1

  2. LiteraturePresent

    647 matched papers (436 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 (ASS1).

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?

647

647 papers have been published on this condition. That is a real research literature — still far smaller than common diseases (breast cancer: over 700,000 papers). Median papers in the last 10 years for a rare disease in this dataset (publications denominator n=5449) is 41.

647 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).

436 in the last 10 years · high confidence · 89th percentile (publications denominator)

Phrase hits: 647 · MeSH hits: 0

Open Europe PMC search

Who's working on it?

1,419

Distinct author names in 200 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
    Häberle J12 papers · 2026

    University Children's Hospital and Children's Research Center, Zurich, Switzerland.

    Papers in Europe PMC
  2. 02
    Kölker S11 papers · 2026

    Division of Pediatric Neurology and Metabolic Medicine, Center for Pediatric and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany.

    Papers in Europe PMC
  3. 03
    Zielonka M11 papers · 2026

    Division of Pediatric Neurology and Metabolic Medicine, Center for Pediatric and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany.

    Papers in Europe PMC
  4. 04
    Garbade SF10 papers · 2026

    Division of Pediatric Neurology and Metabolic Medicine, Center for Pediatric and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany.

    Papers in Europe PMC
  5. 05
    Hoffmann GF10 papers · 2026

    Division of Pediatric Neurology and Metabolic Medicine, Center for Pediatric and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany.

    Papers in Europe PMC
  6. 06
    Nagamani SCS10 papers · 2026

    Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.

    Papers in Europe PMC
  7. 07
    Posset R10 papers · 2026

    Division of Pediatric Neurology and Metabolic Medicine, Center for Pediatric and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany.

    Papers in Europe PMC
  8. 08
    Gleich F9 papers · 2026

    Division of Pediatric Neurology and Metabolic Medicine, Center for Pediatric and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany.

    Papers in Europe PMC
  9. 09
    Gropman AL9 papers · 2026

    Division of Neurodevelopmental Pediatrics and Neurogenetics, Children's National Health System and The George Washington School of Medicine, Washington, District of Columbia.

    Papers in Europe PMC
  10. 10
    Nakamura K7 papers · 2026

    Department of Pediatrics Kumamoto University Kumamoto Japan.

    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. 2 trials are registered for citrullinemia, the broader category — shown separately because they may or may not enrol this specific subtype.

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.

Broader category: citrullinemia

2

Interventional trials for the parent category, exclusive of NCT IDs already counted above. Eligibility for this subtype is not guaranteed.

Worth raising with a clinician. How we count trials.

Observational and natural-history studies

3 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.

Recruiting or not-yet-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 Urea cycle disorder as a category (Groups 1 and 2), and this condition is a form of it. Confirm eligibility with a Centre of Excellence.

Group 1 — one-time curative treatment

Up to ₹50 lakh per patient

Financial support for treatment at notified Centres of Excellence (figures evolved from the original ₹20 lakh Group-1 ceiling).

Policy figures change. Verify current MoHFW / CoE guidance before relying on any amount. Verify

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.

"Citrullinemia type I" OR "ASS deficiency" OR "Argininosuccinate synthase deficiency" OR "Argininosuccinate synthetase deficiency" OR "Argininosuccinic acid synthase deficiency" OR "Argininosuccinic acid synthetase deficiency" OR "CTLN1" OR "Citrullinemia type 1" OR "Classic citrullinemia"

Run this search on Europe PMC

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

"Citrullinemia type I" OR "ASS deficiency" OR "Argininosuccinate synthase deficiency" OR "Argininosuccinate synthetase deficiency" OR "Argininosuccinic acid synthase deficiency" OR "Argininosuccinic acid synthetase deficiency" OR "CTLN1" OR "Citrullinemia type 1" OR "Classic citrullinemia" OR "ASS1"

Recall-expansion terms: ASS1

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 · 3 observational · 0 expanded access. Only interventional studies enter the trial headline.

Parent-category trials query:

"citrullinemia"

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

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 2026-07-27T10:32:18.802Z