Which conditions are associated with webbed feet (partial or complete syndactyly of the toes)?

Webbed Feet: Associated Conditions

Webbed feet (toe syndactyly) is most commonly associated with craniosynostosis syndromes, particularly Apert syndrome and Pfeiffer syndrome, as well as synpolydactyly caused by HOXD13 mutations.

Primary Syndromic Associations

Apert Syndrome (Acrocephalosyndactyly Type I)

Apert syndrome consistently presents with foot syndactyly alongside craniosynostosis and midface retrusion 1. The foot manifestations range from:

• Complete fusion of all toes with a central nail mass (most severe)
• Syndactyly of the second through fifth toes with medially deviated great toe (hallux varus)
• Tarsal bone fusions and other anatomical variants 1

The foot deformities in Apert syndrome are often underestimated and neglected in clinical management, despite causing significant shoe-fitting problems and abnormal plantar pressures 1.

Pfeiffer Syndrome

Pfeiffer syndrome type 1, caused by FGFR2 mutations (such as c.758C>G), presents with variable severity of syndactyly affecting both hands and feet 2. Key features include:

• Craniosynostosis with midfacial hypoplasia
• Broad thumbs and toes
• Webbing or fusion of fingers and toes with variable expressivity
• Associated complications including hearing loss and tracheal stenosis 2

Synpolydactyly (SPD)

This rare condition results from HOXD13 gene mutations and has distinctive features 3:

• Pathognomonic webbing between the third and fourth fingers
• Webbing between the fourth and fifth toes
• Partial or complete digit duplication within the syndactylous web
• The genotype-phenotype correlation varies depending on whether mutations affect the DNA binding domain, polyalanine tract, or other regions 3

Rare Syndromic Associations

Ectodermal Dysplasia-Syndactyly Syndrome Type 1 (EDSS1)

Caused by PVL4 gene mutations, this exceedingly rare condition (reported in only 10 families worldwide) presents with 4:

• Bilateral cutaneous syndactyly of third and fourth web spaces in hands
• Bilateral toe syndactyly involving second through fourth toes
• Sparse, brittle hair, eyebrows, and eyelashes
• Abnormal dentition and nails

Clinical Approach Algorithm

When evaluating webbed feet, systematically assess:

1. Craniofacial examination: Look for craniosynostosis, midfacial hypoplasia, or abnormal skull shape (suggests Apert or Pfeiffer syndrome)

2. Hand examination:

   • Third-fourth finger webbing with duplication → synpolydactyly 3
   • Broad thumbs with syndactyly → Pfeiffer syndrome 2
   • Third-fourth web space syndactyly → EDSS1 4

3. Ectodermal features: Sparse hair, abnormal teeth, brittle nails → EDSS1 4

4. Foot pattern specificity:

   • Complete toe fusion with central nail mass → severe Apert 1
   • Fourth-fifth toe webbing with duplication → synpolydactyly 3
   • Second-fourth toe syndactyly with hallux varus → Apert 1

5. Genetic testing: Confirm with FGFR2 testing (Apert/Pfeiffer), HOXD13 testing (synpolydactyly), or PVL4 testing (EDSS1) based on clinical phenotype

Critical Management Considerations

Interdisciplinary care is mandatory involving orthopedics, neurosurgery, genetics, and pediatrics 2. For Apert syndrome specifically, plantar pressure measurements using pedobarography should be performed to document biomechanical abnormalities and guide treatment decisions 1.

The functional benefit of surgical syndactyly separation in feet remains undetermined, though it is frequently performed for shoe-fitting problems 1. Conservative management with insoles and orthopedic shoes may alleviate abnormal plantar pressures before considering surgery 1.