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ORPHA:773

Adult Refsum disease

high confidenceDisorder

Also known as: Classic Refsum disease · HMSN 4 · HMSN IV · Hereditary motor and sensory neuropathy type 4 · Hereditary motor and sensory neuropathy type IV · Heredopathia atactica polyneuritiformis · Phytanic-CoA hydroxylase deficiency

Publications

1,926

90.1th percentile

Trials

3

Interventional, condition-specific

Researchers

1,101

Distinct authors in sample

Gene link

PHYH

Definitive

Readiness

3/6

Stages with a signal

Clinical definition (Orphanet)

A disease characterized by anosmia, cataract, early-onset retinitis pigmentosa and possible neurological manifestations, including peripheral and cerebellar . Other features can be deafness, ichthyosis, skeletal abnormalities, and cardiac arrhythmia. It is characterized biochemically by accumulation of phytanic acid in plasma and tissues.

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 (17)

HMSN type IV · HSMN IV · Refsum Disease · Refsum disease · Refsum disease, adult, 1 · Refsum disease, classic · Refsum's disease · adult Refsum disease · adult Refsum disease due to PHYH · classic Refsum disease · hereditary motor and sensory neuropathy 4 · hereditary motor and sensory neuropathy type 4 · hereditary sensory and motor neuropathy type 4 · heredopathia atactica polyneuritiformis · hypertrophic neuropathy of Refsum · phytanic acid oxidase deficiency · phytanic-CoA hydroxylase 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.”

3/6 stages with a signal

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

  1. Gene identifiedPresent

    Definitive — PHYH

  2. LiteraturePresent

    1,926 matched papers (493 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

    3 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 (PHYH).

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?

1,926

1,926 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.

1,926 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).

493 in the last 10 years · high confidence · 90.1th percentile (publications denominator)

Phrase hits: 1,926 · MeSH hits: 29

Open Europe PMC search

Who's working on it?

1,101

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
    Gibberd FB16 papers · 2010

    Refsum's Disease Clinic, Chelsea & Westminster Hospital, 369 Fulham Road, London SW10 9NH, UK.

    Papers in Europe PMC
  2. 02
    Billimoria JD7 papers · 1989
    Papers in Europe PMC
  3. 03
    Wierzbicki AS7 papers · 2026

    Department of Chemical Pathology, St. Thomas' Hospital, London, UK. Anthony.Wierzbicki@kcl.ac.uk

    Papers in Europe PMC
  4. 04
    Clemens ME6 papers · 1989
    Papers in Europe PMC
  5. 05
    Sidey MC6 papers · 2010
    Papers in Europe PMC
  6. 06
    Wanders RJA6 papers · 2025

    Laboratory Genetic Metabolic Diseases, Department of Clinical Chemistry, Amsterdam UMC, Location AMC, University of Amsterdam, The Netherlands.

    Papers in Europe PMC
  7. 07
    Feher MD5 papers · 2016

    Adult Refsum Disease Clinic, Chelsea & Westminster Hospital, London, UK.

    Papers in Europe PMC
  8. 08
    Leroy BP5 papers · 2026

    Department of Ophthalmology, Ghent University and Ghent University Hospital, Corneel Heymanslaan 10, 9000 Ghent, Belgium.

    Papers in Europe PMC
  9. 09
    Michaelides M4 papers · 2025

    Moorfields Eye Hospital NHS Foundation Trust, London, UK.

    Papers in Europe PMC
  10. 10
    Waterham HR4 papers · 2023

    Laboratory Genetic Metabolic Diseases, Department of Clinical Chemistry, Amsterdam UMC, Location AMC, University of Amsterdam, The Netherlands.

    Papers in Europe PMC

Clinical research

Is a treatment being tested?

3

interventional trials for this specific condition

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

Data as of 27 July 2026

3 interventional trials — more than 73% of diseases in the trials denominator have none at all (5114 of 7003; this disease is at the 85.1th percentile).

high confidence · 85.1th percentile (trials denominator)

Recruiting interventional trials

From the matched ClinicalTrials.gov set

3 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

General rare disease registries you may be eligible for

These studies enroll across many rare conditions. They are not counted as evidence that anyone is studying this specific disease.

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

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.

"Adult Refsum disease" OR "Classic Refsum disease" OR "HMSN 4" OR "HMSN IV" OR "Hereditary motor and sensory neuropathy type 4" OR "Hereditary motor and sensory neuropathy type IV" OR "Heredopathia atactica polyneuritiformis" OR "Phytanic-CoA hydroxylase deficiency" OR "HMSN type IV" OR "HSMN IV" OR "Refsum Disease" OR "Refsum disease, adult, 1" OR "Refsum disease, classic" OR "Refsum's disease" OR "adult Refsum disease due to PHYH" OR "hereditary motor and sensory neuropathy 4" OR "hereditary sensory and motor neuropathy type 4" OR "hypertrophic neuropathy of Refsum" OR "hypertrophic neuropathy of the Refsum" OR "phytanic acid oxidase deficiency"

Run this search on Europe PMC

MeSH descriptor terms unioned into the query: Refsum disease with increased pipecolic acidemia; Refsum Disease

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

"Adult Refsum disease" OR "Classic Refsum disease" OR "HMSN 4" OR "HMSN IV" OR "Hereditary motor and sensory neuropathy type 4" OR "Hereditary motor and sensory neuropathy type IV" OR "Heredopathia atactica polyneuritiformis" OR "Phytanic-CoA hydroxylase deficiency" OR "HMSN type IV" OR "HSMN IV" OR "Refsum Disease" OR "Refsum disease, adult, 1" OR "Refsum disease, classic" OR "Refsum's disease" OR "adult Refsum disease due to PHYH" OR "hereditary motor and sensory neuropathy 4" OR "hereditary sensory and motor neuropathy type 4" OR "hypertrophic neuropathy of Refsum" OR "hypertrophic neuropathy of the Refsum" OR "phytanic acid oxidase deficiency" OR "Refsum disease with increased pipecolic acidemia" OR "PHYH"

Recall-expansion terms: PHYH

Interventional trials matched via: both, 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: 3 interventional · 3 observational · 0 expanded access. Only interventional studies enter the trial headline.

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

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 2026-07-26T15:18:21.233Z