Overview
Polydactyly of a triphalangeal thumb (bilateral) is a rare congenital hand condition present at birth in which both thumbs have an extra bone segment (three phalanges instead of the normal two), making them look more like fingers, and there may also be extra digits (polydactyly) on one or both hands. This condition is classified as 'OBSOLETE' in the Orphanet database, meaning it has been reclassified or merged into a broader diagnostic category. Triphalangeal thumb can occur as an isolated finding or as part of a larger syndrome. When the thumb has three bones, it may appear longer than usual, may not oppose (move toward the other fingers) normally, and may have reduced grip strength. In some cases, there is a fully formed extra thumb or finger alongside the triphalangeal thumb. The condition is typically noticed at birth during a physical examination. Treatment usually involves surgical correction to improve hand function and appearance. Orthopedic or plastic surgeons who specialize in hand surgery can reconstruct the thumb to restore a more typical shape and improve the ability to grasp objects. Outcomes after surgery are generally good, especially when performed early in childhood. Because this entry is now obsolete, patients and families should look for updated classifications such as 'triphalangeal thumb' or 'preaxial polydactyly' for the most current medical information.
Key symptoms:
Thumbs that look unusually long, more like fingersExtra finger or thumb on one or both handsDifficulty gripping or pinching objectsThumbs that do not bend or oppose normallyReduced hand strengthUnusual appearance of the hands at birthDifficulty with fine motor tasks like buttoning clothesFlat or finger-like thumb without normal thumb curvature
Autosomal dominant
Passed on from just one parent; each child has about a 50% chance of inheriting it
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for OBSOLETE: Polydactyly of a triphalangeal thumb, bilateral.
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Specialists
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Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to OBSOLETE: Polydactyly of a triphalangeal thumb, bilateral.
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Caregiver Resources
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Questions for your doctor
Bring these to your next appointment
- Q1.Is my child's triphalangeal thumb an isolated finding or part of a genetic syndrome?,What is the best age for surgical correction?,What type of surgery will be performed, and how many procedures might be needed?,What hand function can we expect after surgery?,Should we pursue genetic testing for our family?,Will my child need occupational therapy, and for how long?,Are there any other body systems we should check given this diagnosis?
Common questions about OBSOLETE: Polydactyly of a triphalangeal thumb, bilateral
What is OBSOLETE: Polydactyly of a triphalangeal thumb, bilateral?
Polydactyly of a triphalangeal thumb (bilateral) is a rare congenital hand condition present at birth in which both thumbs have an extra bone segment (three phalanges instead of the normal two), making them look more like fingers, and there may also be extra digits (polydactyly) on one or both hands. This condition is classified as 'OBSOLETE' in the Orphanet database, meaning it has been reclassified or merged into a broader diagnostic category. Triphalangeal thumb can occur as an isolated finding or as part of a larger syndrome. When the thumb has three bones, it may appear longer than usual,
How is OBSOLETE: Polydactyly of a triphalangeal thumb, bilateral inherited?
OBSOLETE: Polydactyly of a triphalangeal thumb, bilateral follows a autosomal dominant inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does OBSOLETE: Polydactyly of a triphalangeal thumb, bilateral typically begin?
Typical onset of OBSOLETE: Polydactyly of a triphalangeal thumb, bilateral is neonatal. Age of onset can vary across affected individuals.