Overview
Postaxial polydactyly type B, unilateral, is a condition where a baby is born with an extra small finger or toe on the outer side (the side of the pinky finger or little toe) of one hand or one foot. The term 'postaxial' means the extra digit is on the outer edge of the hand or foot. In type B, the extra digit is usually small, soft, and poorly formed — often described as a small nub or skin tag rather than a fully developed finger or toe. The word 'unilateral' means it affects only one side of the body. This entry is now labeled as 'OBSOLETE' in medical classification systems, meaning it has been merged into a broader category of postaxial polydactyly for classification purposes. However, the condition itself still occurs and is one of the most common congenital limb differences seen at birth. Treatment is usually straightforward. In many cases, the small extra digit can be removed shortly after birth by tying it off with a suture (if it is a small skin tag) or through a minor surgical procedure. The condition typically does not affect a child's overall health, development, or life expectancy. It can occur as an isolated finding or sometimes as part of a broader genetic syndrome, so a medical evaluation is recommended to rule out other associated conditions.
Key symptoms:
Extra small finger or toe on the outer side of the hand or footSmall skin tag or nub near the pinky finger or little toeSoft, poorly formed extra digitExtra digit present on only one hand or one footThe extra digit may or may not have a small nailThe extra digit may be attached by a thin stalk of skin
Variable
Can be inherited in different ways depending on the underlying gene
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for OBSOLETE: Postaxial polydactyly type B, unilateral.
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Specialists
View all specialists →No specialists are currently listed for OBSOLETE: Postaxial polydactyly type B, unilateral.
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: Postaxial polydactyly type B, unilateral.
Community
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Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
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Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.Does my child's extra digit contain any bone, and how does that affect treatment?,Is this an isolated finding, or could it be part of a genetic syndrome?,What is the best method for removing the extra digit in my child's case?,When is the ideal time to have the extra digit removed?,Should we see a geneticist or have genetic testing done?,What is the chance that future children could also have this condition?,What should I watch for after the extra digit is removed?
Common questions about OBSOLETE: Postaxial polydactyly type B, unilateral
What is OBSOLETE: Postaxial polydactyly type B, unilateral?
Postaxial polydactyly type B, unilateral, is a condition where a baby is born with an extra small finger or toe on the outer side (the side of the pinky finger or little toe) of one hand or one foot. The term 'postaxial' means the extra digit is on the outer edge of the hand or foot. In type B, the extra digit is usually small, soft, and poorly formed — often described as a small nub or skin tag rather than a fully developed finger or toe. The word 'unilateral' means it affects only one side of the body. This entry is now labeled as 'OBSOLETE' in medical classification systems, meaning it has
At what age does OBSOLETE: Postaxial polydactyly type B, unilateral typically begin?
Typical onset of OBSOLETE: Postaxial polydactyly type B, unilateral is neonatal. Age of onset can vary across affected individuals.