Kisho

Kisho is an information platform, not a medical provider. Nothing on this site constitutes medical advice, diagnosis, or treatment recommendations. All content is aggregated from publicly available sources (including ClinicalTrials.gov, PubMed, FDA.gov, and Orphanet) and is provided for informational purposes only. Clinical trial eligibility, treatment decisions, and any health-related actions should always be discussed with a qualified healthcare professional. Kisho does not endorse any specific therapy, organization, or clinical trial. Terms of use · Privacy policy

mesoaxial synostotic syndactyly with phalangeal reduction (MSSD) - Clinical Profile, Genes & Research | Kisho | Kisho

Rare Disease

mesoaxial synostotic syndactyly with phalangeal reduction

MONDO:0012271

Also known as:MSSDsyndactyly type 9syndactyly, Malik-Percin type

Overview

Mesoaxial synostotic syndactyly (MSSD) with phalangeal reduction is a novel and distinct form of non-syndromic syndactyly including complete syndactyly of the 3rd and 4th fingers with synostoses of the corresponding metacarpals and associated single phalanges, syndactyly of the 2nd and 3rd toes and 5th finger clinodactyly.

GeneticsAutosomal recessive · BHLHA9 (chr 17)

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: Aplasia/Hypoplasia of the middle phalanx of the 5th finger, Proximal/middle symphalangism of 5th finger, Aplasia/Hypoplasia of the hallux, and 3-4 finger osseus syndactyly and 5 more.

Organ System	Phenotype Count	Example Features
Arms and legs	5	Aplasia/Hypoplasia of the middle phalanx of the 5th finger, Proximal/middle symphalangism of 5th finger, 3-4 finger osseus syndactyly

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.

BHLHA9 encodes basic helix-loop-helix family member a9 (235 aa). Transcription factor, which play a role in limb development. Is an essential player in the regulatory network governing transcription of genes implicated in limb morphogenesis Highest expression in Brain Frontal Cortex BA9 (1.3 TPM) and Brain Cortex (1.1 TPM).

Mesoaxial synostotic syndactyly with phalangeal reduction is associated with mutations in the BHLHA9 gene on chromosome 17.

BHLHA9 is classified as a druggable target (Transcription Factor category) with score 0.0.

Diagnosis

Genetic testing for BHLHA9 is available. Testing is considered confirmatory for diagnosis.

Prognosis

Estimated prevalence: <1 in 1,000,000 (VERY_RARE).

Data assembled from 5 of 12 sources · Last updated Sep 20, 2026, 1:48 AM UTC

MONDOHPOClinicalTrials.govFDAPubMedHGNCClinVarClinGenGeneReviewsOrphanetOMIMRUSP

Medical References

External Resources

OMIM

Online Mendelian Inheritance in Man

OMIM:609432

Orphanet

European rare disease database

Orphanet:157801

GARD

Genetic and Rare Diseases Info Center

GARD:10590

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?

← Back to All Diseases

mesoaxial synostotic syndactyly with phalangeal reduction

Overview

Clinical Presentation

Genetic Landscape

Diagnosis

Prognosis

Medical References

External Resources

OMIM

Orphanet

GARD

Related Diseases

Questions for Your Care Team

Questions for Your Care Team

Explore clinical features