Triphalangeal Thumb Polydactyly

Triphalangeal thumb (TPT) is the hallmark feature in individuals with mutations in the zone of polarizing activity regulatory sequence (ZRS), which is contained within intron 5 of the LMBR1 gene. Mutations in ZRS have been reported in individuals with PPD2 (TPT with or without preaxial polydactyly), TPT polysyndactyly, syndactyly IV (complete syndactyly with polydactyly), and Werner mesomelic syndrome (tibial hypoplasia, polysyndactyly, TPT).

Tests Available

Forms and Documents

Test Details

  • Confirmation of a clinical diagnosis
  • Differentiation from other causes of syndromic and isolated limb abnormalities
  • Prenatal diagnosis in families with a known mutation
  • Capillary Sequencing


4 weeks
2-5 mL Blood - Lavender Top Tube
Oral Rinse (30-40 mL)|Buccal Swabs


  • 759.7 Multiple congenital anomalies, so described Congenital: anomaly, multiple NOS deformity, multiple NOS
  • 755 Other congenital anomalies of limbs Excludes: those deformities classifiable to 754.0-754.8
  • 755.00 Polydactyly, unspecified digits Supernumerary digits
  • 755.1 Syndactyly Symphalangy Webbing of digits
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