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ORPHA:85287

X-linked intellectual disability, Siderius type

low confidenceDisorder

Publications

1,490

Trials

0

Interventional, condition-specific

Researchers

267

Distinct authors in sample

Gene link

PHF8

Definitive

Readiness

4/6

Stages with a signal

Clinical definition (Orphanet)

X-linked , Siderius type is characterised by mild to borderline intellectual deficit associated with cleft lip/palate. Preaxial polydactyly, large hands and cryptorchidism are sometimes present. The syndrome has been described in seven boys from two families. Transmission is X-linked and the syndrome is caused by mutations in the PHF8 gene, localised to the p11.21 region of the X chromosome.

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 (7)

MRXSSD · Siderius X-linked intellectual disability syndrome · Siderius X-linked mental retardation syndrome · Siderius-Hamel syndrome · intellectual developmental disorder, X-linked, syndromic, Siderius type, X-linked recessive · intellectual disability syndrome, X-linked, Siderius type · syndromic X-linked intellectual disability Siderius type

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.”

4/6 stages with a signal

No matched interventional trial, but a gene association and an animal model are on record — often described as translation-ready / stalled at the clinical step.

  1. Gene identifiedPresent

    Definitive — PHF8

  2. LiteraturePresent

    1,490 matched papers (1,084 in last 10 years) Source

  3. Phenotype characterisedPresent

    31 HPO annotations (e.g. Upslanted palpebral fissure; Sloping forehead; Large hands) Source

  4. Animal modelPresent

    1 genotype model (Mus musculus) Source

  5. Orphan designationNot found

    No FDA or EMA orphan-drug designation matched this disease via UMLS or preferred name Source

  6. Interventional trialNot found

    No matched interventional trial under our ClinicalTrials.gov rules

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 (PHF8).

GenCC classification: Definitive.

Phenotypes (Monarch / HPO)

31

Associated phenotypes · MONDO:0010286

  • Upslanted palpebral fissure
  • Sloping forehead
  • Large hands
  • Cleft palate
  • Microcephaly

Showing 5 of 31 — open Monarch for the full list.

Animal models (Monarch / Alliance)

1

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)

No designation matched this disease via UMLS or preferred name on the FDA OOPD mirror or EMA orphan register. Absence here is not proof that none exists under another wording.

Open Targets candidates

No drugs or clinical candidates returned for this Mondo ID on Open Targets.

CTD chemicals (MyDisease.info)

No CTD chemical associations returned for this Mondo ID.

Literature

Is anyone studying this?

1,490

1,490 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.

1,490 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).

1,084 in the last 10 years · low confidence

Phrase hits: 41 · MeSH hits: 1

Open Europe PMC search

Who's working on it?

267

Distinct author names in 41 sampled papers — named people below.

Who's working on it?

No interventional trial matched this name; these authors publish on it in the sampled literature — a practical starting point for contact.

  1. 01
    Martínez-Balbás MA3 papers · 2026

    Department of Molecular Genomics, Instituto de Biología Molecular de Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona 08028, Spain.

    Papers in Europe PMC
  2. 02
    van Bokhoven H3 papers · 2022

    Department of Human Genetics, Donders Institute for Brain, Behaviour and Cognition, Radboudumc, Nijmegen, The Netherlands.

    Papers in Europe PMC
  3. 03
    Asensio-Juan E2 papers · 2017

    Department of Molecular Genomics, Instituto de Biología Molecular de Barcelona, Spanish Research Council (CSIC), Barcelona Science Park, Barcelona 08028, Spain.

    Papers in Europe PMC
  4. 04
    de la Cruz X2 papers · 2026

    Vall d'Hebron Institute of Research (VHIR), Passeig de la Vall d'Hebron, 119, E-08035 Barcelona, Spain.

    Papers in Europe PMC
  5. 05
    Fortschegger K2 papers · 2011

    Center for Genomic Regulation, Barcelona Biomedical Research Park, 08003 Barcelona, Spain.

    Papers in Europe PMC
  6. 06
    Gallego C2 papers · 2017

    Department of Cell Biology, Instituto de Biología Molecular de Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona 08028, Spain.

    Papers in Europe PMC
  7. 07
    Iacobucci S2 papers · 2026

    Department of Molecular Genomics, Instituto de Biología Molecular de Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona 08028, Spain.

    Papers in Europe PMC
  8. 08
    Kalscheuer VM2 papers · 2022

    Max Planck Institute for Molecular Genetics, Research Group Development and Disease, Ihnestr. 63-73, 14195 Berlin, Germany.

    Papers in Europe PMC
  9. 09
    Kremp M2 papers · 2026

    Institut für Biochemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.

    Papers in Europe PMC
  10. 10
    Lee JH2 papers · 2017

    Department of Biological Sciences, Konkuk University, Seoul 05029, Korea. kingmega@konkuk.ac.kr.

    Papers in Europe PMC

Clinical research

Is a treatment being tested?

0

interventional trials for this specific condition

No interventional trial testing a treatment matched this specific condition name on ClinicalTrials.gov (observational studies and pan-disease registries are listed separately when present).

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

No matched interventional trials. This is true for 77.2% of diseases in the trials denominator (5501 of 7126). Here are the researchers publishing on it.

low confidence · 38.6th percentile (trials denominator)

Recruiting interventional trials

From the matched ClinicalTrials.gov set

No interventional trial testing a treatment was found for this specific condition name on ClinicalTrials.gov.

See who's working on it — people publishing on this disease are often the practical next contact when no trial is listed.

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 0 · after dedupe 0 · already on CT.gov 0 · kept 0 · parent 0 · uncertain 0 · dropped 0 · fetched 2026-07-30

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).

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 X-linked intellectual disability, Siderius type — 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.

("X-linked intellectual disability, Siderius type" OR "MRXSSD" OR "Siderius X-linked intellectual disability syndrome" OR "Siderius X-linked mental retardation syndrome" OR "Siderius-Hamel syndrome" OR "intellectual developmental disorder, X-linked, syndromic, Siderius type, X-linked recessive" OR "intellectual disability syndrome, X-linked, Siderius type" OR "syndromic X-linked intellectual disability Siderius type") OR (MESH:"Siderius X-linked mental retardation syndrome") OR ("PHF8" OR "PHF8 syndrome" OR "PHF8-related")

Run this search on Europe PMC

MeSH descriptor terms unioned into the query: Siderius X-linked mental retardation syndrome

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

"X-linked intellectual disability, Siderius type" OR "MRXSSD" OR "Siderius X-linked intellectual disability syndrome" OR "Siderius X-linked mental retardation syndrome" OR "Siderius-Hamel syndrome" OR "intellectual developmental disorder, X-linked, syndromic, Siderius type, X-linked recessive" OR "intellectual disability syndrome, X-linked, Siderius type" OR "syndromic X-linked intellectual disability Siderius type"

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

Query health: ok — strategies attempted: phrase, mesh; 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
  • Publication count (1490) is implausibly high for prevalence class "<1 / 1 000 000" — treat as possible over-matching, not a measure of research intensity

Ingested 2026-07-27T02:52:56.135Z