What is polydactyly

Polydactyly is a condition in which a person has more than 5 fingers per hand or 5 toes per foot. Polydactyly is the most common birth defect of the hand and foot. Polydactyly can occur as an isolated finding such that the person has no other physical anomalies or intellectual impairment. However, polydactyly can occur in association with other birth defects and cognitive abnormalities as part of a genetic syndrome.

Polydactyly can be broadly classified as ¹⁾:

• Pre-axial polydactyly: extra digit(s) towards the thumb/hallux (radially) – extra first digit
• Post-axial polydactyly: extra digit(s) towards little finger/toe (ulnar) – extra fifth digit
• Central polydactyly: central polydactyly involves duplication of the second, third, or fourth digit.

Estimated incidence is different for pre and post-axial polydactyly ²⁾:

• Post-axial polydactyly: ~1 in 3000
• Pre-axial polydactyly: ~1 in 7000
• Central polydactyly is the rarest encountered.

The association of hand and foot polydactyly is uncommon. If hand and foot polydactyly does occur, it may be a case of “crossed polydactyly”—when preaxial involement of the hand and postaxial involvement of the foot occurs or vice versa.

In addition, there may be a greater prevalence in individuals of African descent (particularly for post-axial polydactyly) ³⁾.

Polydactyly or having extra fingers or toes (6 or more) can occur on its own. There may not be any other symptoms or disease present. Polydactyly may be passed down in families. This trait involves only one gene that can cause several variations.

African Americans, more than other ethnic groups, can inherit a 6th finger. In most cases, this is not caused by a genetic disease.

Polydactyly can also occur with some genetic diseases. If polydactyly is an isolated anomaly it is incidental and not of concern but if polydactyly is associated with another anomaly it then carries a vastly variable prognosis dependent on the rest of the syndrome.

Extra digits may be poorly developed and attached by a small stalk. This most often occurs on the little finger side of the hand. Poorly formed digits are usually removed. Simply tying a tight string around the stalk can cause it to fall off in time if there are no bones in the digit.

In some cases, the extra digits may be well-formed and can even function.

In some cases, the extra digits may be well-formed and functional. Surgery may be considered especially for poorly formed digits or very large extra digits. Surgical management depends greatly on the complexity of the deformity ⁴⁾. Larger digits may need surgery to be removed.

Figure 1. Polydactyly

Footnote: A 39-year-old man presented for evaluation of his acne. He had no notable medical history and was taking no medications. Physical examination revealed an incidental finding of six functional digits on his hands and feet. He had no family history of similar findings. Bilateral polydactyly of the hands and feet is rare. The extra digit can be postaxial (occurring along the ulnar aspect of the hand or fibular aspect of the foot), preaxial (occurring along the radial aspect of the hand or tibial aspect of the foot), or central (occurring in the middle of the hand or foot). Polydactyly can occur by itself, typically as a manifestation of autosomal dominant mutations, or in conjunction with a syndrome of congenital anomalies. This patient did not have any additional congenital anomalies associated with the bilateral postaxial polydactyly. No treatment is required for the condition, but surgical removal for cosmesis and comfort is feasible.

[Source ⁵⁾ ]

Preaxial polydactyly

Pre-axial polydactyly refers to polydactyly where the additional digit is towards the first digit of the hand (radial side) or foot (medially).

Pre-axial polydactyly is less common than post-axial polydactyly, with an estimated incidence of 1 in 7000.

Pre-axial polydactyly associations

Pre-axial polydactyly can be associated with:

• Down syndrome
• VATER association
• Holt-Oram syndrome
• Greig cephalopolysyndactyly syndrome
• Carpenter syndrome
• Laurin-Sandrow syndrome
• Fanconi anemia

Post-axial polydactyly

Post-axial polydactyly refers to polydactyly where the additional digit is on the ulnar margin of the hand, or lateral to the 5th toe.

Post-axial polydactyly is more common than pre-axial polydactyly, with an estimated incidence of 1 in 3000.

Postaxial hand polydactyly is a common isolated disorder in black children and autosomal dominant transmission is suspected ⁶⁾. In contrast, postaxial polydactyly seen in white children is usually syndromic and associated with an autosomal recessive transmission. Postaxial polydactyly is approximately 10 times more frequent in blacks than in whites and is more frequent in male children ⁷⁾.

Other factors associated with postaxial hand polydactyly include twinning, low maternal education, parental consanguinity, occurrence in first-degree relatives, and maternal bleeding in the first trimester ⁸⁾.

Post-axial polydactyly has been defined by Temtamy and McKusick as ⁹⁾:

• Type A: additional digit at the metacarpophalangeal joint (or more proximally at the carpometacarpal joint)
• Type B: small nubbin of non-functioning tissue or additional soft tissue on a pedicle

Or, you can use a separate three-part classification system:

• Type 1: nubbin or floating digit
• Type 2: duplications at the metacarpophalangeal joint
• Type 3: duplication of the entire ray

Post-axial polydactyly associations

Post-axial polydactyly can be associated with:

• Patau syndrome (trisomy 13)
• Bardet-Biedl syndrome
• Meckel Gruber syndrome
• McKusick-Kaufman syndrome
• Following oral-facial-digital syndromes (OFDS)
  • Oral-facial-digital syndrome (OFDS) type 2 – Mohr syndrome
  • Oral-facial-digital syndrome (OFDS) type 6
• Certain skeletal dysplasias
  • Chondroectodermal dysplasia – Ellis-van Creveld syndrome
  • Asphyxiating thoracic dysplasia – Jeune syndrome
• Smith Lemli Opitz syndrome
• Certain short rib polydactyly syndromes: e.g types 1 and 3

Polydactyly causes

Polydactyly is the most common congenital digital anomaly of the hand and foot. Polydactyly may appear in isolation or in association with other birth defects. Isolated polydactyly is often autosomal dominant, while syndromic polydactyly is often autosomal recessive ¹⁰⁾.

Current theories on polydactyly focus on mutations in specific genetic locations that cause limb development to go awry ¹¹⁾.

Many specific mutations have been linked to polydactyly; however, a molecular etiology has not been found in a third of human disorders associated with polydactyly ¹²⁾.

Mammals have been shown to have genetic clusters identified as homeobox or Hox genes corresponding to five domains across the limb bud. According to Muragaki et al ¹³⁾, mutations in the HOXD13 gene are associated with synpolydactyly.

The steps in limb development and outgrowth are controlled by at least two described signal centers, as follows ¹⁴⁾:

• Zone of polarizing activity (ZPA) – Sonic Hedgehog is a molecule found to mediate ZPA activity
• Apical ectodermal ridge (AER) – Expresses fibroblast growth factors

As limb growth in utero progresses along a preset timeline, elongation of the limb, development of soft tissue, and differentiation of digits progresses.

Polydactyly causes may include:

• Asphyxiating thoracic dystrophy
• Carpenter syndrome
• Ellis-van Creveld syndrome (chondroectodermal dysplasia)
• Familial polydactyly
• Laurence-Moon-Biedl syndrome
• Rubinstein-Taybi syndrome
• Smith-Lemli-Opitz syndrome
• Trisomy 13 (Patau syndrome)

Polydactyly genetics

A large proportion of polydactyly is isolated although they can be associated with an immense amount of anomalies which include:

• Aneupliodic syndromic
  • Trisomy 13 (Patau syndrome): tends to give post-axial polydactyly
• Non-aneuploidic syndromic
  • Bardet-Biedl syndrome: often post-axial
  • Carpenter syndrome
  • Fetal valproate syndrome
  • Hydrolethalus syndrome
  • Joubert syndrome
  • Juberg-Hayward syndrome
  • Lhermitte duclos disease
  • Meckel Gruber syndrome: tends to be post-axial
  • McKusick-Kaufman syndrome: post-axial ¹⁵⁾
  • Megalencephaly, polymicrogyria, polydactyly, and hydrocephalus (MPPH) syndrome ¹⁶⁾
  • Oral-facial-digital syndromes
    • Oral-facial-digital syndrome (OFDS) type 2 – Mohr syndrome: post-axial
    • Oral-facial-digital syndrome (OFDS) type 6: post-axial ¹⁷⁾
  • Pallister-Hall syndrome
  • Short rib polydactyly syndrome(s) ¹⁸⁾
  • Skeletal dysplasias
    • Asphyxiating thoracic dysplasia ¹⁹⁾
    • Ellis-van Creveld syndrome ²⁰⁾ – chondroectodermal dysplasia
  • Smith-Lemli-Opitz syndrome
  • VACTERL association
• Non-aneuploidic, non-syndromic
  • Macrodystrophia lipomatosa
  • Syndactyly: most common associated limb anomaly, it is then termed polysyndactyly

Table 1. Clinical Entities That Manifest Polydactyly (abbreviations: D = Autosomal dominant inheritance, R = Autosomal recessive inheritance, X = Sex-linked Inheritance, M = Multiple modes of inheritance, U = Unknown inheritance. Highlighted clinical entities are non-syndromic.)

Inheritance	Clinical Entity	Gene
D	Aase Smith Syndrome Type I
R	Achondrogenesis, Type II	COL2A1
R	Acro-Cranio-Facial Dysostosis
R	Acrocallosal Syndrome	GLI3
R	Acrocephalopolysyndactylous Dysplasia
R	Acrocephalosyndactyly Type I
U	Acrofacial Dysostosis
R	Acrofacial Dysostosis-Type Rodriguez
R	Acrofrontofacionasal Dysostosis Type 1
R	Acrofrontofacionasal Dysostosis Type 2
D	Acromelic Frontonasal Dysostosis
D	Acropectoral Syndrome
D	Acropectorovertebral Dysplasia, F-form of
U	Acrorenal
R	Acrorenal-Mandibular Syndrome
U	Adamsbaum (1991) Syndrome
U	Aminopterin Syndrome sine Aminopterin
U	Anandan (2008) Sternal Defects – Aplasia Cutis Congenita-Polydactyly
D	Apert Syndrome	FGFR2
U	Arens (1991) Acrofacial Dysostosis
R	Arimia Syndrome
R	Asphyxiating Thoracic Dystrophy	IFT80, DYNC2H1
D	Atelosteogenesis Type III	FLNB
U	Baisch-Polydactyly; Absent Nails
R	Baller-Gerold Syndrome	RECQL4
U	Baraitser-Brachyphalangy-Polydactyly-Absent Tibiae
U	Barakat (1996) Polydactyly-Osteopenia-Hypoplastic Kidney
R	Bardet-Biedl Syndrome	BBS1, BBS2, ARL6, BBS4, BBS5, MKKS, BBS7, TTC8, BBS9, BBS10, BBS11, BBS12
D	Basal Cell Nevus Syndrome	PTCH1
U	Bates (2002) Acrofacial Dysostosis-Digital Anomalies-Renal Agenesis
D	Beckwith-Wiedemann Syndrome	CDKN1C
R	Biemond Syndrome II
U	Bitoun (1994)-Glaucoma-Thumb Anomalies-Joint Dislocations
R	Blair (2000) Autosomal Recessive Craniosynostosis Syndrome
R	Bloom Syndrome	RECQL3
R	Bonneau Syndrome
D	Brachydactyly (Preaxial) Hallux Varus-Thumb Abduction
D	Brachydactyly Type B	ROR2
D	Brachydactyly Type C	GDF5
D	Brachyphalangy, Polydactyly, and Tibial Aplasia/Hypoplasia
U	Braddock (2003) Laryngeal Webs; CHD; Vertebral Defects
D	Branchiooculofacial Syndrome	TFAP2A
R	Braun (1962) Nephrosis; Deafness; Brachytelephalangy
X	BRESHECK
U	Brunoni (1984) Radial Aplasia; Short Stature; Unusual Face
D	C Syndrome	CD96
D	C-LIKE Syndrome	CD96
R	Camptobrachydactyly
R	Carpenter Syndrome	RAB23
U	Carpenter-Hunter-Micromelia; Polysyndactyly; Encephalocele; Fragile Bones
U	Cerebro-fronto-facial Syndrome Type III
R	Cerebrofaciothoracic Dysplasia
D	Cerebrooculonasal Syndrome
D	CHAR Syndrome	TFAP2B
D	CHARGE Syndrome	CHD7, SEMA3E
U	Chitayat (1993) Hyperphalangism; Hallux Valgus; Bronchomalacia
R	Chitty (1993) Bowed Tibiae; Radial Anomalies; Osteopenia; Fractures
U	Chondrodysplasia-Situs Inversus-Cystic Pancreatic Dysplasia
R	Chondrodysplasia, Grebe Type	GDF5
X	Chonrdodysplasia Punctata 2, X-Linked Dominant	EBP
R	Cleft Lip/Palate with Characteristic Facies, Intestinal Malrotation, and Lethal Congenital Heart Disease
U	COH Syndrome-Craniosynostosis; Bifid Thumb; Micropenis
D	Colobomas-Brachydactyly (Type Sorsby)
U	Craniofacial Malformations, Asymmetric, with Polysyndactyly and Abnormal Skin and Gut Development
X	Craniofrontonasal Syndrome	EFNB1
D	Culler (1984) Hypopituitarism; Postaxial Polydactyly
U	Cutis Aplasia-Blue Sclerae-Hypertelorism-Polydactyly-Hypoplastic Nipples
U	Cutis Marmorata Telangiectasia Congenita
R	Dandy-Walker Malformation with Postaxial Polydactyly
D	De Smet Complex Synpolydactyly	FBLN1
D	Deafness, Congenital and Onychodystrophy, Autosomal Dominant
U	Deafness, Onychodystrophy, Triphalangeal Thumbs
R	Desbuquois (1966)-Chondrodystrophy; Advanced Bone Age	CANT1
R	Diamond-Blackfan	RPS19, RPL5, RPL11
U	Disorganization, Mouse, Homolog of
U	Donnai (1988) Meckel-like Syndrome
R	DOOR
U	Double Nail For Fifth Toe
D	Duane-Radial Ray Syndrome	SALL4
U	Duplication of Lower Limb-Plus
U	Ectodermal Dysplasia Syndrome with Distinctive Facial Appearance and Preaxial Polydactyly of Feet
M	Ectrodactyly-Autosomal Dominant	WNT10A
R	Ectrodactyly-Polydactyly
R	Eiken (1984) Retarded Ossification; Abnormal Modeling of Bones	PTHR1
R	Ellis-Van Creveld Syndrome	EVC, EVC2
R	Encephalocele-Radial, Cardiac, Gastrointestinal, Anal/renal Anomalies
R	Endocrine-Cerebrosteodysplasia	ICK
R	Engelhard (1979) Pre- and Postaxial Polysyndactyly; Ptosis
R	Faciocardiomelic Syndrome
R	Fanconi Pancytopenia Syndrome	FANCA, FANCB, BANCC, FANCD1, FANCD2, FANCE, FANCF, XRCC9, FANCI, FANCJ, PHF9, FANCM, FANCN, FANCO
R	Fibular Aplasia or Hypoplasia, Femoral Bowing and Poly-, Syn-, and Oligodactyly	WNT7A
U	Femoral-Facial Syndrome
U	Ferda Percin-Yilmaz-Syn-Poly-Oligo-Brachydactyly
U	Fibular Aplasia-Anonychia-Finger Polydactyly-Toe Oligodactyly
U	Fibular Hemimelia-Polysyndactyly
D	Floating-Harbor-Short Stature-Delayed Bone Age-Broad Nose
U	Focal Dermal Hypoplasia, Morning Glory Anomaly, and Polymicrogyria
X	Focal Dermal Hypoplasia	PORCN
U	Franceschini (1994) Mask-Like Face; Ear Anomalies; Digital Malformations
D	Frias Syndrome
M	Frontonasal Dysplasia	ALX3
U	Fryns-Aftimos
U	Fryns-Lagae-Rizzo-Polydactyly-Growth Retardation-Spasticity-Urogenital
U	Gandhi (2008)
U	Garrett-Tripp-MR; Polydactyly; Hair Absence; Dermatitis; Perthe’s Disease
U	Giant Diencephalic Hamartoma-Facial Cleft-Ear and Eye Anomalies
U	Goiter, Multinodular, Cystic Renal Disease, and Digital Anomalies
R	Goossens (2006) Congenital Heart Disease-Polydactyly-Ectopic Neuropituitary
D	Greig Cephalopolysyndactyly Syndrome	GLI3
U	Growth and Mental Retardation, Mandibulofacial Dysostosis, Microcephaly, and Cleft Palate
U	Gül (2000)-Craniofacial Anomalies
R	Guschmann (2001) Mesomelic Campomelia-Polydactyly-Dandy-Walker
R	Hallux Varus and Preaxial Polysyndactyly
U	Hameed (1999) Acrocraniofacial Syndrome
U	Happle-Tinschert Syndrome
U	Hartsfield (1984) Holoprosencephaly; Ectrodactyly; Cleft Face
R	Heart-hand-Type 4-with Mesoaxial Hexadactyly
U	Hemifacial Microsomia-Radial Defects
U	Hemihypertrophy-Hemimegalencephaly-Polydactyly
R	Hernandez (1985) Cortical Blindness; Polydactyly; Mental Retardation
R	Hirschsprung Disease with Heart Defects, Laryngeal Anomalies, and Preaxial Polydactyly
R	Hirschsprung Disease with Polydactyly, Renal Agenesis, and Deafness
R	Hirschsprung Disease with Ulnar Polydactyly, Polysyndactyly of Big Toes, and Ventricular Septal Defect
U	Ho (1975) Cleft Palate; Congenital Heart Disease; Absent Tibia; Polydactyly
U	Holmes-Schimke-Microcephaly; CHD; Skeletal Abnormalities
D	Holprosencephaly 9	GLI2
D	Holt-Oram Syndrome	TBX5
R	Holzgreve Syndrome
R	Huang (1999) Hirschsprung, Congenital Heart Defect, Laryngeal Anomalies
R	Hydrolethalus Syndrome 1	HYLS1
R	Hydrops-Ectopic Calcification-Moth-Eaten Skeletal Dysplasia	LBR
D	Hypomelia with Müllerian Duct Anomalies
M	Hypoplastic Left Heart-Postaxial Polydactyly
U	Johnson (1974) Glossopalatine Ankylosis; Cataracts; Abnormal Digits
U	Johnson Neuroectodermal Syndrome
M	Joubert Syndrome; JBTS	CXORF5, INPP5E, TMEM216, RPGRIP1L
U	Kantaputra (2003) Symphalangism; Multiple Frenula; Polydactyly; Dental Anomalies
D	Klippel-Trenaunay-Weber Syndrome
R	Kondoh (2001) Microcephaly-growth Retardation-Atopic Dermatitis-Mental Retardation
R	Kozlowski-Krajewska-Polydactyly-Brachydactyly-Uncombable Hair-Mental Retardation
D	Lacrimoauriculodentodigital Syndrome	FGFR2, FGFR3, FGF10
R	Lambotte (1990) Microcephaly, Large Ears, Polydactyly, Hypoplastic Thumb
U	Lampert (1984)-Craniostenosis; Polydactyly
U	Landy-Donnai-Split Hand; Hydrops; Renal Anomalies
U	Laryngomalacia-Plus
R	Lathosterolosis	SC5DL
D	Laurin-Sandrow Syndrome
X	Lenz Microphthalmia
U	Linear Nevus Sebaceous Syndrome
R	Liver Fibrocystic Disease and Polydactyly
U	Macrocephaly-Capillary Malformation
U	Mandibulofacial Dysostosis-Type Guion-Almeida
U	Mardini (1985) Lung Agenesis; Congenital Heart Disease; Thumb Anomalies
D	Martin-Gorski-Ocular Malformations-polydactyly-membranous Bone Abnormal
D	Martinez-Frias (1995) Distal Aphalangia; Syndactyly; Microcephaly
U	Martsolf (1977) Skeletal Dysplasia; Polydactyly; Pierre Robin
U	McGaughran (1998) Micrognathia-Syndactyly
R	McKusick (1968) Cataract; Unilateral Limb Defects
R	McKusick-Kaufman Syndrome	MKKS
R	Meckel Syndrome	CC2D2A, CEP290, MKS1, TMEM67, RPGRIP1L
R	Megalencephaly Polymicrogyria-Polydactyly Hydrocephalus Syndrome
R	Megalocornea-Mental Retardation Syndrome
U	Meningocoele-Renal Dysplasia-Postaxial Polydactyly
R	Mental Retardation, Congenital Heart Disease, Blepharophimosis, Blepharoptosis and Hypoplastic Teeth
R	Mental Retardation, Truncal Obesity Retinal Dystrophy, and Micropenis	INPP5E
R	Microcephaly with Mental Retardation and Digital Anomalies
U	Microcephaly, Corpus Callosum Dysgenesis, and Cleft Lip/Palate
R	Microphthalmia with Limb Anomalies
D	Microphthalmia, Syndromic 6	BMP4
R	Mildenberger (1998) Diffuse Mesangial Sclerosis-Dandy-Walker-polydactyly
U	Mirror-Image Polydactyly	MIPOL1
M	Moebius
R	MOHR Syndrome
U	Morava (2004) Focal Skin Defect-Microphthalmia-Limb Defects
R	Morton (1998) Lethal Skeletal Dysplasia-Ectopic Digits
R	Müllerian Derivatives Persistence of, with Lymphangiectasia and Postaxial Polydactyly
R	Multiple Maternal Hypomethylation Syndrome
X	Multiple Pterygium Syndrome, X-Linked
U	MURCS
D	Nager Acrofacial Dysostosis
U	Neural Tube Defect-Preaxial Polydactyly-Vertebral Anomalies
R	Neuro-Facio-Digito-Renal Syndrome
U	NevusComedonicus Syndrome
R	Nijmegen Immunodeficiency Syndrome	NBN
U	Occult Toe
D	Oculo-dento-digital Syndrome	GJA1
R	Odontotrichomelic Syndrome
U	OEIS
R	Oliver Syndrome
D	Onychonychia-Acral Defects-Cooks	SOX9
U	Opitz (1989) Mandibulofacial Dysostosis; Hexadactyly; Lymphoedema
U	Oral-Facial-Digital Syndrome-Cerebral Dysgenesis
U	Oral-Facial-Digital Syndrome-Type Gabrielli
U	Oral-Facial-Digital Syndrome-Type Stenram
U	Oral-Facial-Digital Syndrome-Type XII
X	Oral-Facial-Digital Syndrome Syndrome I; OFD1	CXORF5
R	Oral-Facial-Digital Syndrome Syndrome III; OFD3
R	Oral-Facial-Digital Syndrome Syndrome IV; OFD4
R	Oral-Facial-Digital Syndrome Syndrome IX; OFD9
D	Oral-Facial-Digital Syndrome Syndrome V; OFD5
R	Oral-Facial-Digital Syndrome Syndrome VI; OFD6
X	Oral-Facial-Digital Syndrome Syndrome VIII; OFD8
D	Oral-Facial-Digital Syndrome Syndrome X; OFD10
R	Orstavik (1992) Oral-Cardiac-Digital Syndrome
U	Osteochondrodysplasia-Osteopenia-Preaxial Polydactyly
X	Otopalatodigital Syndrome, Type II	FLNA
D	Pallister-Hall Syndrome; PHS	GLI3
R	Panigrahi (2002) Ptosis Polydactyly Mental Retardation
U	Parentin-Perissutti Single Incisor-Duane-Bifid Thumb
U	Pavone (1991) Connective Tissue Disorder; Polydactyly
U	Percin and Percin (2003) An Unusual Syndactyly
R	Peters’ Anomaly-Microphthalmia-Arhinia
U	Pfeiffer-Angerstein-Bowing-Bone Dysplasia
R	Pfeiffer-Mayer-Coloboma; Polydactyly; Mental Retardation
R	Phadke (1999) Complex Camptopolydactyly
U	Piepkorn (1977) Short Ribs; Polydactyly
U	Polydactyly-Colobomata-Hypopituitarism-Cleft Palate
U	Polydactyly-Palmar Type
U	Polydactyly-Panfollicular Nevus
U	Polydactyly-Renal Vascular Malformation
U	Polydactyly-Obstructive Uropathy
M	Polydactyly, Postaxial	GLI3
U	Polydactyly, Postaxial, with Dental and Vertebral Anomalies
D	Polydactyly, Postaxial, with Progressive Myopia
D	Polydactyly, Preaxial I
D	Polydactyly, Preaxial II; PPD2	SHH ZRS
D	Polydactyly, Preaxial III
D	Polydactyly, Preaxial IV	GLI3
U	Polymetatarsia-Without Polydactyly.
U	Polysyndactyly-Delta Phalanges
R	Polysyndactyly with Cardiac Malformation
D	Polysyndactyly, Crossed
R	Postaxial Acrofacial Dysostosis	DHODH
D	Postaxial Oligodactyly, Tetramelic
U	Postaxial Polydactyly-Atrium Anomaly
U	Postaxial Polydactyly-Single Atrium-Mental Retardation
D	Preaxial Deficiency Postaxial Polydactyly, and Hypospadias	HOXA13
R	Pseudotrisomy 13 Syndrome
D	Radial Defects-Deafness (IVIC)
X	Radioulnar Synostosis-Radial Ray Anomalies
R	Reinitis Pgmentosa 41	PROML1
R	Renal Dysplasia; Limb Defects
R	Renal-Hepatic-Pancreatic Dysplasia	NPHP3
M	Rhombencephalosynapsis
U	Rippberger (1976) BBB-like Syndrome with Brachydactyly
D	Robinow Syndrome	ROR2
D	Robinow-Sorauf Syndrome	TWIST
D	Rubinstein-Taybi Syndrome	CBP
U	Sakati-Nyhan-Acrocephalopolysyndactyly Type III
U	Say (1987) Clover-leaf Skull; Skeletal Dysplasia
U	Scalp Defects and Postaxial Polydactyly
R	Schinzel-Giedion Midface-Retraction Syndrome	SETBP1
D	Schmitt Hypoplastic Radius, Hypospadias, Maxillary Diastema
R	Sener (1990) Synpolydactyly
U	Shepherd (1989) Noonan-like Syndrome
U	Short Rib-polydactyly Syndrome (Kannu-Aftimos)
R	Short Rib-Polydactyly Syndrome, Type I
R	Short Rib-Polydactyly Syndrome, Type II
R	Short Rib-Polydactyly Syndrome, Type III	DYNC2H1
R	Short Rib-Polydactyly Syndrome, Type IV
X	Siderius X-Linked Mental Retardation Syndrome	PHF8
X	Simpspn-Golabi-Behmel Syndrome, Type I	GPC3
D	Sinha-Verma-Postaxial and Mesoaxial Polydactyly
U	Situs Inversus-Polydactyly-Broad Thumbs
R	Sjogren-Larsson-Like Syndrome with Bone Dysplasia
R	Smith-Lemli-Opitz Syndrome	DHCR7
D	Split-Hand/Foot Malformation
R	Spondylocaroptarsal Synostosis Syndrome	FLNB
U	Spondylocostal Dysostosis-Preaxial Polydactyly
R	Spondylocostal Dysostosis	DLL3
U	Stoll-Gasser-Hepatic Ductal Plate Anomalies; Digital Anomalies; Congenital Heart Disease
U	Sugiura-Lenz (1999) Polysyndactyly
U	Sulko (2010) Tibial Hemimelia-Preaxial Polydactyly-Heart Defects
D	Syndactyly-Polydactyly-Earlobe Syndrome
D	Syndactyly, Type IV	SHH ZRS
D	Synpolydactyly 1; SPD1	HOXD13
D	Synpolydactyly 2; SPD2	FBLN1
D	Tabatznik Syndrome
U	Tarhan (2004) Mental Retardation, Polysyndactyly, Deafness, Facial Dysmorphism
U	Thai Symphalangism Syndrome
D	Thanatophoric Dysplasia, Type I	FGFR3
U	Thumb Hypoplasia-Preaxial Toe Polydactyly
R	Tibia, Absence of Hypoplasia of, with Polydactyly, Retrocerebellar Arachnoid Cyst, and Other Anomalies
U	Tibia, Absence of, with Polydactyly
D	Tibia, Hypoplasia of, with Polydactyly
D	Tibial Aplasia Ectrodactyly Syndrome
M	Tibial Hemimelia
D	Tibial Hemimelia-Polydactyly-Club Foot	PITX1
U	Tollner (1981) Polydactyly; Visceral Anomalies
D	Townes-Brocks Syndrome	SALL1
U	Triangular Thumb Epiphysis-Angulation Deformity
D	Triphalangeal Thumb, Nonopposable
D	Triphalangeal Thumbs and Dislocation of Patella
D	Triphalangeal Thumbs with Brachyectrodactyly Ulna and Fibula, Absence of, with Severe Limb
R	Deficiency	WNT7A
R	Ulnar Hypoplasia with Mental Retardation
M	Ulnar Ray Dysgenesis with Postaxial Polydactyly and Renal Cystic Dysplasia
D	Ulnar-Mammary Syndrome	TBX3
R	Urbach (1986) Skeletal Dysplasia; Rhizomelia of Humeri
R	Urioste (1996) Limb Deficiency-Vertebral Hypersegmentation-Absent Thymus
U	VACTERL Association-Tibial Aplasia
U	VATER Association
R	VATER-Like Defects with Pulmonary Hypertension, Laryngeal Webs, and Growth Deficiency
U	Weaver Syndrome	NSD1
D	Weyers Acrofacial Dysostosis	EVC
U	Wieczorek (2002) Thumb Aplasia-Radial Aplasia-Microcephaly	ZBTB16
U	Wiedemann (1985c) Macrocephaly; Polydactyly of Toes; Tibial Defect
U	Wolter (1971) Papilla Nigra; Cleft Palate; Extra Thumb
D	WT Syndrome-Pancytopenia-Hand Defects
D	Zannolli (2008) Polydactyly-Ectodermal Dysplasia

[Source ²¹⁾ ]

Table 2. Genes that, when mutated, can cause more than one clinically distinct phenotype in humans

Gene	Clinical Entity
CD96	C syndrome C-like syndrome
CXORF5	Joubert syndrome* Oral-facial-digital syndrome type I
DYNC2H1	Asphyxiating thoracic dystrophy type 3 Short-Rib polydactyly syndrome
EVC	Ellis-Van Creveld syndrome Weyers acrofacial dysostosis
FBLN1	De Smet complex synpolydactyly Synpolydactyly*
FGFR2	Apert syndrome Lacrimoauriculodentodigital syndrome
FLNB	Atelosteogenesis type III Spondylocarpotarsal dysostosis
GDF5	Brachydactyly type C Chondrodysplasia, Grebe type
GLI3	Greig cephalopolysyndactyly syndrome Pallister-Hall syndrome Acrocallosal syndrome Polydactyly, postaxial Polydactyly, preaxial*
INPP5B	Joubert syndrome* Mental retardation, truncal obesity, retinal dystrophy, and micropenis
MKKS	Bardet-Biedl syndrome McKusick-Kaufman syndrome
ROR2	Brachydactyly type B Robinow syndrome
RPGRIP1L	Joubert syndrome* Meckel Syndrome
SHH**	Polydactyly, preaxial* Synpolydactyly*
WNT7A	Fibular a/hypoplasia, femoral bowing and poly-, syn-, and oligodactyly Ulna and fibula, absence of, with severe limb deficiency

Footnotes:

* These phenotypes can be caused by mutations in more than one of the genes listed in the left column.
**These mutations are in the SHH ZRS (ZPA regulatory sequence) and not in the SHH gene proper

[Source ²²⁾ ]

Polydactyly symptoms

Most of the time, polydactyly is discovered at birth when the baby is still in the hospital. Polydactyly may be present as an isolated finding, or they may occur as part of a syndrome, in which case other abnormalities are usually present.

Polydactyly diagnosis

Your health care provider will diagnose polydactyly based on your family history, medical history, and a physical exam.

Medical history questions may include:

• Have any other family members been born with extra fingers or toes?
• Is there a known family history of any of the disorders linked to polydactyly?
• Are there any other symptoms or problems?

Tests used to diagnose polydactyly:

• Chromosome studies
• Enzyme tests
• X-rays
• Metabolic studies

You may want to make a note of polydactyly in your personal medical record.

Extra digits may be discovered the first 3 months of pregnancy with ultrasound or a more advanced test called embryofetoscopy.

Prenatal ultrasound

Fetal finger buds can be seen using transvaginal ultrasound as early as 9 weeks and reliably by 13 weeks of pregnancy. Once polydactyly is established, a thorough ultrasound evaluation, especially of the heart, nervous system, limbs, and kidneys, to identify an associated syndrome (e.g., Meckel-Gruber syndrome, trisomy 13) should be performed. Follow-up ultrasound between 17 and 34 weeks with biometric profile is recommended to establish the diagnosis of isolated polydactyly ²³⁾.

Radiographs

Radiographs of the affected limb are recommended to show whether the rudimentary digit contains skeletal elements. The degree of deviation of the digit and the size of the articulating metacarpal or metatarsal also may be helpful in surgical planning.

Polydactyly treatment

A child with distal extremity anomalies experiences emotional stress ²⁴⁾. By age 3 years, the child has become aware of the anomaly. By age 7 years, the child has begun to experience the close scrutiny of his peers at school. For these reasons, along with others, surgical correction should be initiated early in life.

Polydactyly surgery

Surgical management depends greatly on the complexity and location of the deformity. Traditionally, postaxial polydactyly was managed by pediatricians with suture ligation and only syndactyly was treated in the operating room. However, the increased risk of painful neuromas when using suture ligation has led to the use of sharp excision for postaxial polydactyly. The accessory digital nerve in postaxial polydactyly needs to be identified and transected as far proximally as is safe in order to decrease the risk of neuroma. Soft tissue then covers the end of the divided nerve. In cases of preaxial and central polydactyly, treatment is variable and the surgeon looks to find a balance between aesthetics and functionality. Waiting until age 9-12 months is advisable to decrease anesthesia risk ²⁵⁾.

Conversely, if an infant has postaxial type B polydactyly (rudimentary extra digit attached to the ulnar side by a soft tissue stalk), excision in the neonatal nursery is a safe and simple procedure with consistently positive outcomes. Excision is done with a single swipe of a scalpel after the use of topical anesthesia ²⁶⁾.

Polydactyly surgery complications

Complications in the perioperative timeframe include those secondary to bleeding and anesthesia.

Later, decreased function due to ligamentous laxity or contracture can occur. Painful neuromas can also occur at the treatment site, especially when using suture ligation as therapy ²⁷⁾.