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ORPHA:56

Alkaptonuria

medium confidenceDisorder

Also known as: Hereditary ochronosis · Homogentisic acid oxidase deficiency

Publications

2,678

87th percentile

Trials

6

Interventional, condition-specific

Researchers

885

Distinct authors in sample

Gene link

HGD

Definitive

Readiness

6/6

Stages with a signal

Clinical definition (Orphanet)

A rare inborn error of metabolism disorder characterized by homogentisic acid accumulation causing dark urine.

How rare: 1-9 / 1 000 000 — roughly one to nine people per million. In a city the size of Kolkata, perhaps a few dozen.

Orphanet entry

Cross-references

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

Additional Mondo synonyms (5)

alcaptonuria · alkaptonuria · hereditary ochronosis · homogentisate 1,2-dioxygenase deficiency · homogentisic acid oxidase deficiency

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.”

6/6 stages with a signal

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

  1. Gene identifiedPresent

    Definitive — HGD

  2. LiteraturePresent

    2,678 matched papers (913 in last 10 years) Source

  3. Phenotype characterisedPresent

    75 HPO annotations (e.g. Mitral valve calcification; Ochronosis; Dark cerumen) Source

  4. Animal modelPresent

    2 genotype models (Mus musculus) Source

  5. Orphan designationPresent

    1 FDA · 2 EMA designations (1 FDA orphan-indication approval) — e.g. nitisinone Source

  6. Interventional trialPresent

    6 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 (HGD).

GenCC classification: Definitive.

Phenotypes (Monarch / HPO)

75

Associated phenotypes · MONDO:0008753

  • Mitral valve calcification
  • Ochronosis
  • Dark cerumen
  • Brown pigmentation of the conjunctiva
  • Arthropathy

Showing 5 of 75 — open Monarch for the full list.

Animal models (Monarch / Alliance)

2

Model associations linked to this Mondo ID

Monarch fetch 2026-07-29

Therapies

Designations, candidates, and chemicals

FDA OOPD and EMA orphan designations, Open Targets clinical candidates, and CTD chemical associations via MyDisease.info. These never change the interventional-trial headline.

Orphan designation (FDA · EMA)

3

Designations · 1 with FDA orphan-indication approval

  • FDA nitisinoneAlkaptonuria · 2001-10-19 · Not FDA Approved for Orphan Indication
  • EMA methotrexateTreatment of alkaptonuria · 29/08/2016 · PositiveEMA designation
  • EMA nitisinoneTreatment of alkaptonuria · 13/03/2002 · WithdrawnEMA designation

Sources: FDA OOPD · EMA orphan designations

Open Targets candidates

1

Drugs / clinical candidates · MONDO_0008753

CTD chemicals (MyDisease.info)

No CTD chemical associations returned for this Mondo ID.

Literature

Is anyone studying this?

2,678

2,678 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=3967) is 59.

2,678 papers since the earliest indexed year in this search — median last-10-year count for a rare disease in this dataset is 59 (publications denominator n=3967).

913 in the last 10 years · medium confidence · 87th percentile (publications denominator)

Phrase hits: 2,671 · MeSH hits: 0

Open Europe PMC search

Who's working on it?

885

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
    Ranganath LR17 papers · 2026

    Department of Clinical Biochemistry and Metabolic Medicine, Royal Liverpool University Hospital, Prescot Street, Liverpool, L7 8XP, UK.

    Papers in Europe PMC
  2. 02
    Gallagher JA14 papers · 2026

    Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool L69 3BX, UK.

    Papers in Europe PMC
  3. 03
    Santucci A13 papers · 2026

    Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Italy.

    Papers in Europe PMC
  4. 04
    Bou-Gharios G11 papers · 2026

    William Henry Duncan Building University of Liverpool Liverpool UK.

    Papers in Europe PMC
  5. 05
    Imrich R11 papers · 2025

    1Biomedical Research Center, Slovak Academy of Sciences, Bratislava, Slovakia.

    Papers in Europe PMC
  6. 06
    Ranganath L11 papers · 2026

    3Liverpool University Hospitals NHS Foundation Trust, Liverpool, UK.

    Papers in Europe PMC
  7. 07
    Olsson B9 papers · 2025

    Garriguella AB, 179 62 Ekerö, Sweden.

    Papers in Europe PMC
  8. 08
    Trezza A9 papers · 2026

    ONE-HEALTH Lab, Department of Biotechnology, Chemistry and Pharmacy, University of Siena Via Aldo Moro, 53100 Siena, Italy.

    Papers in Europe PMC
  9. 09
    Hughes JH7 papers · 2026

    Department of Musculoskeletal and Ageing Science, Institute of Life Course and Medical Science, University of Liverpool, Liverpool, UK.

    Papers in Europe PMC
  10. 10
    Introne WJ7 papers · 2025

    Human Biochemical Genetics Section, Medical Genetics Branch, Office of the Clinical Director, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.

    Papers in Europe PMC

Clinical research

Is a treatment being tested?

6

interventional trials for this specific condition

6 interventional trials matched this specific condition name; none in our sample are currently recruiting.

Data as of 11 September 2026 · last trial check 28 July 2026

6 interventional trials — more than 77.2% of diseases in the trials denominator have none at all (5501 of 7126; this disease is at the 90.1th percentile).

medium confidence · 90.1th percentile (trials denominator)

Recruiting interventional trials

From the matched ClinicalTrials.gov set

6 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

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

Other registries (secondary)

Broader net from EU CTIS, ISRCTN, and ICTRP when available — deduped against ClinicalTrials.gov IDs already counted above. Dual-model LLM relevance gates what we keep. These rows are not added to the interventional headline.

raw 1 · after dedupe 1 · already on CT.gov 0 · kept 0 · parent 0 · uncertain 1 · dropped 0 · fetched 2026-07-29

Source notes: ictrp: Error: ICTRP public search unavailable (WHO portal is SPA-only; SOAP needs partnership). Tried: https://apps.who.int/tri

No secondary-registry studies passed dual-model relevance for this condition name (after dedupe).

Uncertain / not reviewed (1)

Where to find support

Condition-specific patient organisations, when Orphanet lists them, are on the disease’s Orphanet page. We also link umbrella groups that support undiagnosed and ultra-rare families.

Orphanet entry for Alkaptonuria — check Associations / patient organisations on that page.

India — NPRD

Last verified 2026-07-26

This ORPHAcode is not on our curated NPRD list (direct or Mondo-parent match). That does not decide clinical eligibility; families in India should ask a notified Centre of Excellence about current coverage.

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.

("Alkaptonuria" OR "Hereditary ochronosis" OR "Homogentisic acid oxidase deficiency" OR "alcaptonuria" OR "homogentisate 1,2-dioxygenase deficiency") OR ("HGD syndrome" OR "HGD-related")

Run this search on Europe PMC

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

"Alkaptonuria" OR "Hereditary ochronosis" OR "Homogentisic acid oxidase deficiency" OR "alcaptonuria" OR "homogentisate 1,2-dioxygenase deficiency"

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

Query health: ok — strategies attempted: phrase; with hits: phrase

Run this search on ClinicalTrials.gov

Confidence reasoning

  • Preferred label is short or not clearly distinctive
  • No synonyms dropped by stoplist
  • No label/synonym collisions with other diseases in this corpus

Ingested 2026-07-26T12:15:41.692Z