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polydactyly of a biphalangeal thumb (PPD1) - Clinical Profile, Genes & Research | Kisho | Kisho

Rare Disease

polydactyly of a biphalangeal thumb

MONDO:0008269

Also known as:PPD1polydactyly, preaxial type 1preaxial polydactyly type 1

Overview

Polydactyly of a biphalangeal thumb or PPD1 is the most common form of preaxial polydactyly of fingers, a limb malformation syndrome, that is characterized by the duplication of one or more skeletal components of a biphalangeal thumb. Hands are preferentially affected (in bilateral), and the right hand is more commonly involved than the left.

GeneticsAutosomal recessive · GLI1 (chr 12)

ResearchLimited published research (2 articles)

Clinical Presentation

Built from Human Phenotype Ontology (HPO) phenotype annotations and GeneReviews clinical descriptions. Features represent findings documented across known cases — not an exhaustive list of possible symptoms.

Features include: Preaxial hand polydactyly, Radial deviation of thumb terminal phalanx, and Partial duplication of thumb phalanx.

Organ System	Phenotype Count	Example Features
Arms and legs	1	Preaxial hand polydactyly

Explore clinical features

Genetic Landscape

Assembled from HGNC gene records, ClinGen gene-disease validity evidence, and ClinVar pathogenic variant data. Validity classifications reflect the strength of published evidence linking each gene to this disease.

GLI1 encodes GLI family zinc finger 1 (1,106 aa). Acts as a transcriptional activator. Binds to the DNA consensus sequence 5'-GACCACCCA-3'. Regulates the transcription of specific genes during normal development. Highest expression in Nerve Tibial (46.2 TPM) and Testis (10.5 TPM).

Polydactyly of a biphalangeal thumb is associated with mutations in the GLI1 gene on chromosome 12.

GLI1 is classified as a druggable target (Clinically Actionable and Transcription Factor categories) with score 5.0.

Diagnosis

Genetic testing for GLI1 is available. Testing is considered confirmatory for diagnosis.

Research Landscape

Sourced from ClinicalTrials.gov and PubMed. Publication types are classified using NLM-curated article metadata; research type breakdowns reflect the nature of published work for this disease.

No clinical trials have been registered for polydactyly of a biphalangeal thumb.

2 publications have been identified in PubMed for polydactyly of a biphalangeal thumb. Research spans Case Report / Case Series (50%) and Epidemiology / Natural History (50%).

Recent Publications

El Fid K (2026). [PMID: 42003052](https://pubmed.ncbi.nlm.nih.gov/42003052/). *Pediatr Dermatol*. [Case Report / Case Series]
Inaba N (2024). [PMID: 37882671](https://pubmed.ncbi.nlm.nih.gov/37882671/). *The Journal of hand surgery, European volume*. [Epidemiology / Natural History]

Data assembled from 6 of 12 sources · Last updated Sep 20, 2026, 1:55 AM UTC

MONDOHPOClinicalTrials.govFDAPubMedHGNCClinVarClinGenGeneReviewsOrphanetOMIMRUSP

Medical References

External Resources

OMIM

Online Mendelian Inheritance in Man

OMIM:174400

Orphanet

European rare disease database

Orphanet:93339

GARD

Genetic and Rare Diseases Info Center

GARD:4417

Questions for Your Care Team

→Should my partner and I meet with a genetic counselor to discuss carrier status and family planning?
→Are there specialists or centers of excellence for this condition in my area?
→Is there a patient registry I should consider joining?

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polydactyly of a biphalangeal thumb

Overview

Clinical Presentation

Explore clinical features

Genetic Landscape

Diagnosis

Research Landscape

Recent Publications

Medical References

External Resources

OMIM

Orphanet

GARD

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Questions for Your Care Team

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