Autosomal dominant preaxial polydactyly means a person is born with one or more extra digits on the preaxial side of a limb—the thumb side of the hand or the big-toe side of the foot—because of a change in a gene that can be passed from parent to child in an autosomal dominant way. “Autosomal” means the gene is on a non-sex chromosome, so males and females can be affected equally. “Dominant” means a single altered copy of the gene is enough to cause the trait. The extra digit may be small and soft-tissue only, or it may be a fully formed bone with joints, tendons, nerves, and blood vessels. This condition often happens by itself (isolated), but sometimes it is part of a broader genetic syndrome (for example, GLI3-related syndromes or enhancer changes that alter the limb-patterning signal called SHH). The most common extra digit on the hand is an extra thumb. Doctors use X-rays and physical exams to understand the exact anatomy, and they use surgery to improve function and appearance when needed. Genetic testing can identify the underlying cause and help with family planning. [1–10]
Autosomal dominant preaxial polydactyly means a baby is born with an extra digit on the thumb (radial) side of the hand or big-toe (hallux) side of the foot. “Autosomal dominant” describes the inheritance: a single copy of a changed gene from one parent can be enough to pass on the trait. The extra digit may be small and soft-tissue only, or fully formed with bone and joints. It often causes little pain, but it can affect grip, pinch, shoe fit, or appearance. Treatment aims to build one, stable, well-aligned thumb or great toe with good strength and motion; this is usually done with surgery in early childhood, followed by hand/foot therapy. PMC+2PMC+2
Other names
Preaxial polydactyly (general term)
Radial polydactyly (when it involves the thumb side of the hand)
Thumb duplication (a very common form; classified by the Wassel system)
Triphalangeal thumb (a thumb with three phalanges; often part of the spectrum)
Tibial preaxial polydactyly (big-toe side of the foot)
Triphalangeal thumb–polysyndactyly syndrome (TPT-PS) (a familial autosomal dominant form)
Greig cephalopolysyndactyly (GCPS) (a GLI3-related syndrome that can include preaxial polydactyly)
Werner mesomelic dysplasia / Laurin–Sandrow spectrum (ZRS/LMBR1 rearrangements with preaxial digits)
“PPD” (preaxial polydactyly) types used in genetics literature (e.g., PPD-I, PPD-II), overlapping with thumb/hallux variations. [2–9,11–16]
Types
1) By limb and side
Thumb (radial) side of the hand: the classic “extra thumb.”
Big-toe (tibial) side of the foot: an extra big toe or duplicated first ray. [3–6]
2) By skeletal pattern (Wassel classification for thumb duplication)
Wassel I–VII: based on which bones are duplicated and where the split occurs.
I–II involve the distal phalanx;
III–IV the proximal phalanx (IV is most common);
V–VI the metacarpal;
VII is triphalangeal thumb (three phalanges).
This system guides surgical planning and prognosis. [4,5,17]
3) By associated features
Isolated (only the extra digit)
With triphalangeal thumb
Polysyndactyly (extra digits plus webbing)
Syndromic (part of a broader syndrome such as GCPS or TPT-PS). [2,7–9,12–16]
4) By genetic mechanism (useful for counseling)
ZRS (zone of polarizing activity regulatory sequence) enhancer variants in LMBR1 intron 5 that mis-activate the SHH limb program anteriorly (preaxially).
GLI3 variants (haploinsufficiency or specific changes) producing a spectrum from isolated preaxial digits to GCPS.
Structural variants (duplications/inversions) in the ZRS region causing dosage or positional effects. [6–9,12–16,18–22]
Causes
In many families, more than one mechanism can appear similar on exam. The items below cover the major, well-described causes and contexts.
ZRS point variants (in the LMBR1 intron 5 enhancer of SHH)
Small, single-letter DNA changes in the ZRS lead to ectopic SHH expression on the thumb/big-toe side during limb development. This abnormal signal tells the early limb bud to “build” an extra preaxial digit. Inheritance is often autosomal dominant with variable expression—some relatives may have a small nub; others may have a fully formed extra thumb or toe. [6–9,12–16,18–22]ZRS duplications
A larger copy-number change (duplication) increases the enhancer’s effect, boosting SHH signaling where it normally should be silent. Families often show triphalangeal thumbs and polysyndactyly across generations. [12–16,20–22]ZRS structural rearrangements (inversions/translocations)
Re-positioning the enhancer relative to SHH or other regulatory landscapes can miswire limb patterning. These structural variants can also be mesomelic (affecting forearm bones) or cause tibial hypoplasia along with preaxial digits. [12–16,20–22]GLI3 haploinsufficiency (Greig cephalopolysyndactyly spectrum)
A truncating change in GLI3, a downstream transcription factor in the SHH pathway, can reduce its normal function and disturb the “digit count and identity” program. Children may have preaxial digits, broad thumbs, and sometimes syndactyly and craniofacial features; expressivity is variable. [7–9,12,19,23]GLI3 missense or specific domain variants
Certain non-truncating changes alter GLI3 activity in a subtler way, tipping the balance of SHH target gene control. The result can be isolated preaxial polydactyly or polysyndactyly without major craniofacial signs. [7–9,12,19,23]Regulatory element changes beyond the canonical ZRS
“Shadow enhancers” and nearby regulatory elements also fine-tune SHH. Variants here are rarer but can phenocopy ZRS defects, producing anterior extra digits. [18–22]Triphalangeal thumb–polysyndactyly syndrome (TPT-PS)
A classic autosomal dominant family pattern—often due to ZRS variants—with thumbs that look like fingers (three bones), extra digits, and sometimes toe involvement. [12–16,20–22]Werner mesomelic dysplasia / Laurin–Sandrow spectrum
Large regulatory rearrangements in the SHH limb domain can cause preaxial digits plus tibial hypoplasia or ulnar/radial anomalies, showing how powerful enhancer topology is for limb shaping. [12–16,20–22]SALL1-related Townes–Brocks spectrum (occasionally preaxial)
Most often known for ear–anal–thumb anomalies, SALL1 changes can sometimes include preaxial polydactyly or triphalangeal thumbs, reminding clinicians to consider broader syndromic contexts. [24]Karyotype-level chromosomal changes affecting 7q36 (SHH region)
Rare deletions/duplications or translocations near SHH can lead to limb mispatterning with preaxial duplication, even when the SHH coding region is intact. [18–22]HOXD cluster regulatory disturbances
While HOXD13 classically causes synpolydactyly/postaxial patterns, altered HOX regulation in development may contribute to unusual preaxial forms in rare families. [25]Maternal diabetes (gestational or pregestational) as a general teratogenic risk
Diabetic embryopathy increases limb anomaly risks overall. It is not a common cause of isolated preaxial polydactyly, but it is an important background risk for limb duplications more generally. [26]Retinoic acid exposure (vitamin A derivatives) in early pregnancy
Excess retinoic acid disturbs limb patterning gradients. Preaxial duplication is uncommon but biologically plausible within the spectrum of limb malformations linked to pathway disruption. [26]Thalidomide/anti-angiogenic exposures (historical/rare today)
These agents can severely alter limb development; although reductions are better known, patterning errors may include duplications. This is historically important but rare now. [26]Amniotic band sequence (mechanical disruption)
Usually causes constrictions or amputations, but in complex sequences, abnormal scarring and budding could secondarily mimic duplication; true genetic preaxial polydactyly is different and typically bilateral/familial. [27]Somatic mosaicism limited to limbs
A post-zygotic variant in ZRS/GLI3 or a regulatory element in a subset of limb cells can create one-sided (unilateral) preaxial duplication while blood testing appears negative. Deep sequencing of affected tissue can reveal the change. [28]Undetected enhancer variants on standard panels
Short-read sequencing may miss some non-coding changes or small structural variants; specialized assays or long-read sequencing later reveal a regulatory cause. [18–22,28]Polygenic/unknown regulatory architecture
Some families show clear autosomal dominant transmission but no single known variant. This suggests other enhancers or modifiers in the SHH/GLI3 network awaiting discovery. [18–22]Syndromic ciliopathies (rare preaxial presentation)
While ciliopathies more often cause postaxial polydactyly, certain modifying backgrounds may rarely present with preaxial duplication due to altered SHH signal transduction through the primary cilium. [29]De novo variants (new in the child)
A child may be the first affected person in the family because the variant arose for the first time in the egg/sperm or very early after conception; if the variant is autosomal dominant, the child can pass it on. [18–23]
Symptoms
Visible extra thumb or big toe
Parents notice a duplicate digit at birth. It can be small or fully formed. Hands are more often noticed because they are always in view. [3–6,17]Difficulty with fine grip
Children may have trouble pinching, writing, or buttoning if the duplicated parts compete for space or pull tendons in different directions. [4,5,17]Thumb instability
If ligaments are split between two thumbs, each can be weak. The child may drop objects or fatigue quickly. [4,5,17]Angular deviation (thumb leaning)
The duplicated bones may push each other so the thumb tilts sideways, making pinch alignment awkward and causing skin pressure points. [4,5,17]Limited motion or stiffness
Two small joints can be less flexible than one normal joint. Scar tissue after repair can also limit motion if not well rehabilitated. [4,5,17]Pain with growth or use
As bones grow, abnormal joint surfaces may rub, causing discomfort after play or sports. Foot cases can hurt in shoes. [3–6,17]Nail deformities
Split or double nails can catch on clothing and are a cosmetic concern for children and families. [4,5]Skin irritation or calluses
Where two digits press together, skin may become sore or thickened, especially in the foot inside tight footwear. [3,4]Tendon imbalance
Duplicated tendons may pull unevenly, causing awkward movement patterns or swan-neck–like deformities in the small thumb. [4,5,17]Numbness or tingling (rare)
Unusual nerve branching may lead to altered sensation, especially after trauma or surgery if protective splints/therapy are not used properly. [4,5]Shoe-wear problems (foot)
An extra big toe makes shoe fitting hard, leading to blisters or pressure pain when walking. [3,4]Cosmetic distress
Children can feel self-conscious; families often request surgery for appearance and social reasons in addition to function. [4,5]Functional asymmetry
If only one hand or foot is affected, tasks that need symmetry (keyboards, sports stances) can feel awkward. [3–6]Activity limitations
Some children avoid climbing frames or ball sports if grip is weak or painful; this can improve after well-planned surgery and therapy. [4,5,17]Family anxiety about heredity
Parents worry about future pregnancies because autosomal dominant inheritance carries about a 50% chance for each child if a pathogenic variant is present. Genetic counseling helps. [1–3,7–9,12]
Diagnostic tests
A) Physical examination (functional/bedside)
General limb inspection
The clinician notes how many digits, their size, nail shape, webbing, and whether both hands/feet are involved. They look for other features suggesting a syndrome (head shape, facial signs). This first step directs imaging and genetic testing. [3–6]Digit palpation and joint mapping
By feeling the bones and joints, the clinician estimates which bones are duplicated and how stable they are, helping to predict the Wassel type before X-rays. [4,5,17]Range-of-motion measurement (goniometry)
Measuring flexion/extension/abduction tells how well each joint moves and what may be lost or gained after reconstruction. [4,5,17]Collateral ligament stress tests at MCP/IP joints
Gentle valgus/varus stress shows whether ligaments are competent or split; instability points to the need for ligament reconstruction during surgery. [4,5,17]Kapandji opposition score (thumb)
The child touches the thumb to different points across the palm; a higher score means better opposition, guiding therapy planning. [4,5]Two-point discrimination (sensory exam)
Simple bedside testing checks nerve territories. Abnormal results alert the surgeon to protect or re-route tiny nerve branches. [4,5]
B) Manual/functional testing (quantified)
Pinch strength (lateral and tip pinch) with a dynamometer
Measures functional pinch; helps set pre- and post-operative goals and track outcomes. [4,5,17]Grip strength (age-adjusted) with a dynamometer
Shows whole-hand function. Lower scores may improve after stable thumb reconstruction. [4,5]Hand function scales (e.g., Pediatric Outcomes Data Collection Instrument)
Standardized questionnaires capture the child’s daily function and symptoms to monitor progress over time. [30]
C) Laboratory and pathological testing
Targeted genetic testing of the ZRS (LMBR1 intron 5) enhancer
Sequencing this small regulatory region detects classic autosomal dominant causes; small duplications may require copy-number assays (MLPA/qPCR). Positive results confirm the mechanism and inform recurrence risk. [12–16,18–22]GLI3 sequencing (± deletion/duplication analysis)
Identifies GLI3-related forms ranging from isolated preaxial digits to GCPS. Detecting a pathogenic variant helps look for and manage associated features. [7–9,12,19,23]Chromosomal microarray (CMA)
Screens for larger deletions/duplications across the genome, including 7q36 (SHH domain) or complex copy-number changes affecting limb enhancers. [18–22]Exome or genome sequencing
Catches atypical or novel regulatory changes missed by panels; trio analysis (child and both parents) clarifies de novo vs inherited status. Long-read genome sequencing can detect complex ZRS rearrangements. [18–22,28]Karyotype (when syndromic features are present)
A broad look for balanced or unbalanced chromosomal changes, helpful if the child has multiple congenital anomalies beyond the hand/foot. [18–22]
D) Electrodiagnostic testing
Nerve conduction studies (select cases)
If there is concern for abnormal sensation, entrapped nerve branches, or atypical numbness, nerve studies can map function and guide surgery; this is uncommon in straightforward pediatric cases. [4,5]Electromyography (EMG) of thenar muscles (rare)
Used when severe tendon imbalance or prior surgery makes muscle function unclear; helps plan tendon transfers in complex reconstructions. [4,5]
E) Imaging
Plain X-rays (hand/foot)
The standard test. X-rays show which bones are duplicated and the Wassel type. They also reveal joint surfaces, growth plates, and metacarpal involvement—critical for surgical planning. [4,5,17]Ultrasound (infant digits)
Useful in very young babies before bones ossify; can show cartilage models, tendons, and tiny vessels; also a gentle, radiation-free way to map anatomy. [31]MRI (complex anatomy or syndromic cases)
Provides detailed images of cartilage, ligaments, nerves, and tendons when plain films are not enough or when revision surgery is planned. [31]Prenatal ultrasound (and, if indicated, fetal MRI) with optional prenatal genetics
Experienced centers can detect limb duplications during pregnancy. If a familial autosomal dominant cause is known, targeted prenatal testing can clarify whether the fetus is affected, with counseling about variability. [31–33]
Non-pharmacological treatments (therapies & other supports)
These do not “shrink” an extra digit—they support function, recovery, and family understanding before/after surgery.
Genetic counseling. Explains inheritance, recurrence risk, and options (including testing when indicated); helps families plan pregnancies and set expectations. PMC
Shared decision-making visits. Multidisciplinary consults (hand/orthopedic surgeon, therapist) to choose timing and approach tailored to Wassel type and child’s needs. OAEPublish
Pre-op hand/foot therapy education. Teaches splint/cast care, swelling control, and how to protect the operative site—reduces complications and speeds return of motion. asht.org
Occupational therapy (hand therapy). After surgery, guided range-of-motion, edema control, scar management, and fine-motor training improve pinch and grasp. asht.org
Physiotherapy for gait (foot cases). For hallux duplication surgeries, targeted exercises and shoe wear advice support balanced walking and toe-off. MedlinePlus
Custom splinting/casting. Short-term immobilization protects repairs, then gradual wean supports tendon balance while preventing stiffness. OAEPublish
Scar care & desensitization. Massage and texture exposure reduce hypersensitivity; silicone gel or sheets may improve scar quality. asht.org
Edema control. Elevation, gentle compression (if advised), and motion sequencing limit swelling that can restrict joint glide. asht.org
Kinesiology taping (therapist-directed). Short-term external support reminders for alignment and edema—used judiciously in pediatrics. asht.org
Adaptive tools. Wider pens, chunky blocks, or modified utensils ease fine-motor tasks during recovery and reduce frustration. asht.org
School/activity accommodations. Temporary note-taking alternatives and PE modifications protect the healing hand/foot. Children’s Hospital of Philadelphia
Parental coaching. Practical guidance on bathing, dressing, and car-seat positioning with casts/splints lowers accidental bumps. Children’s Hospital of Philadelphia
Psychosocial support. Age-appropriate conversations and peer/parent groups reduce stigma and support self-image. Children’s Hospital of Philadelphia
Pain-minimizing strategies. Cold packs (with skin protection), distraction, and scheduled non-opioid analgesics per clinician advice. OAEPublish
Wound-care teaching. Red-flag symptom recognition (increasing redness, drainage, fever) for timely follow-up. OAEPublish
Nutrition for healing. Adequate protein/micronutrients to support tissue repair; no diet can “correct” polydactyly. MedlinePlus
Regular follow-up exams. Watch alignment, joint stability, and growth-related drift; address tendon imbalance early. PMC
Activity pacing. Gradual return to playground/sports to protect repairs while building strength. OAEPublish
Footwear optimization (toes). Roomy toe-box shoes and orthotic guidance reduce pressure points pre-op and after reconstruction. MedlinePlus
Surgery-readiness planning. Choosing the operative window (often ~6–18 months for thumbs) balances safety, growth, and function. PMC
About “Drug treatments” for ADPPD
There are no disease-modifying drugs that eliminate an extra digit or correct the underlying limb-patterning signals after birth. Medicines used around care are supportive (e.g., anesthesia, pain control, antibiotics when indicated) and are chosen individually by your clinician. Below are examples of FDA-labeled medicines commonly used around surgery—not as treatments for polydactyly itself. Always follow your surgeon/anesthesiologist’s orders and the FDA label. OAEPublish
Examples (selected FDA labels):
• Acetaminophen – analgesic/antipyretic for peri-operative pain; label warns about liver toxicity with overdose and total daily dose limits. FDA Access Data+1
• Ibuprofen (NSAID) – analgesic/anti-inflammatory for short-term pain; labels warn about GI, renal, and CV risks and pregnancy cautions. FDA Access Data+1
Because your request asked for “20 drugs…for this disease condition,” I’m not listing twenty—doing so would be misleading. No medicine “treats” polydactyly; surgery is the standard of care, and the FDA cautions against unapproved regenerative claims. PMC+1
Dietary molecular supplements
No supplement can remove an extra digit or change bone patterning. After surgery, a balanced diet with adequate protein, vitamin C, and zinc supports normal wound healing; beyond that, routine megadoses are not recommended without a clinician’s advice. (Use food-first nutrition unless a deficiency is identified.) MedlinePlus
Protein-rich foods (fish, eggs, legumes): support collagen and tissue repair after surgery. MedlinePlus
Vitamin C sources (citrus, berries): co-factor for collagen crosslinking in healing. MedlinePlus
Zinc sources (meat, beans, nuts): supports epithelial repair; avoid excess without testing. MedlinePlus
Whole-grain carbohydrates: fuel for recovery and therapy sessions. MedlinePlus
Healthy fats (olive oil, seeds): help meet energy needs during recovery. MedlinePlus
Dairy or fortified alternatives: calcium for bone health post-op. MedlinePlus
Iron-containing foods (meat/leafy greens): support normal hemoglobin after surgery. MedlinePlus
Hydration plan: helps bowel regularity when activity is decreased post-op. MedlinePlus
High-fiber produce: supports gut health while on pain medicines. MedlinePlus
Limit ultra-processed snacks: they displace nutrient-dense foods needed for healing. MedlinePlus
Immunity-booster / regenerative / stem-cell drugs
No such FDA-approved drugs exist for polydactyly, and “stem cell cures” marketed directly to families are unapproved and have led to serious harms (infections, blindness, disability) in other settings. The FDA repeatedly warns consumers to avoid clinics offering these products outside proper, regulated trials. U.S. Food and Drug Administration+2U.S. Food and Drug Administration+2
Surgeries
Excision of the lesser thumb/ray with reconstruction. The surgeon removes the less functional duplicate and rebuilds ligaments, tendons, and sometimes bone to center and stabilize the remaining thumb for strong pinch/grip; typical timing is in early childhood for safer anesthesia and better remodeling. PMC
Bilhaut-Cloquet procedure (select cases). Portions of both thumbs are combined to create one thumb of near-normal width; used in symmetric duplications; requires meticulous joint and nailbed work to avoid deformity. PMC
Osteotomy and K-wire fixation. Cutting and realigning phalanges or metacarpal bones corrects angulation and improves joint orientation; temporary wires hold the correction while bones heal. OAEPublish
Collateral ligament and tendon balancing. Reconstructing the ulnar/radial collateral ligaments and re-routing tendons restores joint stability and balanced motion for key pinch. OAEPublish
Triphalangeal thumb procedures (when present). Addressing an extra phalanx (Wassel VII) with resection or ulnarization techniques to build a stable, mobile thumb. ScienceDirect
Modern series report good functional and aesthetic results for most children when procedures are matched to the duplication pattern; careful joint reconstruction is crucial to prevent drift or stiffness over time. PMC+1
Prevention
There’s no proven way to “prevent” a genetically driven duplication once conception occurs. Sensible steps focus on healthy pregnancy and informed planning, not cure-claims: maintain prenatal care, manage diabetes, review medicines/teratogen exposures with clinicians, consider genetic counseling if there’s a family history, and use appropriate prenatal imaging. Avoid anyone advertising stem-cell or exosome “prevention” or “corrections.” PMC+2MedlinePlus+2
When to see a doctor
See a pediatric hand/orthopedic specialist soon after birth for assessment, imaging if needed, and a plan for timing of surgery and therapy. Seek urgent care if the digit becomes painful, discolored, or if a postoperative wound shows redness, drainage, fever, or increasing pain. Follow-up through growth is wise to monitor alignment and function. PMC
Foods to emphasize and to limit
Emphasize: lean proteins, beans/lentils, dairy/fortified alternatives, citrus/berries, leafy greens, whole grains, nuts/seeds, olive oil, plenty of water, and high-fiber fruits/veg. Limit: sugary drinks, ultra-processed snacks, trans-fat fried foods, excess sweets, alcohol (adults), excess salt, giant portion sizes, “detox” supplements, megadose vitamins without need, and any product marketed as a stem-cell/exosome “booster.” These choices support normal healing but do not treat polydactyly. MedlinePlus
FAQs
Is it my fault? No—ADPPD reflects genetic/developmental signaling, not something a parent did. PMC
Will it hurt my child? Most infants feel no pain from the extra part itself; issues are function and shoes/gloves fit. Boston Children’s Hospital
Does it go away without surgery? No; extra bone/soft tissue does not disappear. PMC
Best age for surgery? Often in the 6–18 month range for thumbs, individualized by anatomy and health. PMC
Will my child need therapy? Usually yes—hand/foot therapy improves motion, strength, and scar quality after surgery. asht.org
Are results good long-term? Most children achieve a stable, functional, and good-looking thumb with proper technique and follow-up. PMC
What risks exist? As with any surgery: infection, stiffness, imbalance, or residual angulation; experienced teams minimize these. OAEPublish
Will it affect the other hand/foot? Typically only one side is involved; some families have more than one affected member. issh.org
Should we get genetic testing? Consider it if there’s strong family history, syndromic features, or for counseling; ask your genetics team. PMC
What imaging is needed? Simple X-rays usually define bones/joints for planning; advanced imaging is uncommon. PMC
Is splinting a cure? No—splints protect or support; they don’t remove bone or change patterning. OAEPublish
Can vitamins fix it? No supplement corrects digit duplication; nutrition just supports normal healing. MedlinePlus
Is stem-cell therapy an option? No—there are no FDA-approved stem-cell/exosome products for this, and unapproved ones can be dangerous. U.S. Food and Drug Administration
What about toes? Great-toe duplication can affect shoe wear; podiatry/orthopedics plan timing and method similarly to thumbs. MedlinePlus
Where can I read more? See comprehensive surgical reviews and major pediatric centers’ pages on thumb duplication for trustworthy overviews. PMC+1
Disclaimer: Each person’s journey is unique, treatment plan, life style, food habit, hormonal condition, immune system, chronic disease condition, geological location, weather and previous medical history is also unique. So always seek the best advice from a qualified medical professional or health care provider before trying any treatments to ensure to find out the best plan for you. This guide is for general information and educational purposes only. Regular check-ups and awareness can help to manage and prevent complications associated with these diseases conditions. If you or someone are suffering from this disease condition bookmark this website or share with someone who might find it useful! Boost your knowledge and stay ahead in your health journey. We always try to ensure that the content is regularly updated to reflect the latest medical research and treatment options. Thank you for giving your valuable time to read the article.
The article is written by Team RxHarun and reviewed by the Rx Editorial Board Members
Last Updated: October 04, 2025.
