Table 1.
The Nine Non-Syndromic Syndactyly Phenotypes
| Syndactyly | Sub-Groups | Gene | Loci | Phenotype |
|---|---|---|---|---|
| SD1/Zygodactyly | - | 2q34-q36 | Syndactyly of the 3rd + 4th finger web space and/or the web between the 2nd and 3rd toes | |
| Zygodactyly 1 | - | 3p21.31 | Foot zygodactyly without hand or bony involvement | |
| Zygodactyly 2 | - | - | Bilateral cutaneous and/or bony hand and foot involvement | |
| Zygodactyly 3 | - | - | Specific bilateral webbing, cutaneous or bony, of the third + fourth finger | |
| Zygodactyly 4 | - | - | Bilateral cutaneous webbing of the fourth + fifth toe | |
| SD2/Synpolydactyly | SPD 1 | Homeobox D 13 | 2q31.1 | Syndactyly of the third + fourth fingers associated with polydactyly of all components or of part of the fourth finger in the web. Foot polydactyly of the fifth toe included in a web of syndactyly of the fourth + fifth toes |
| SPD 2 | Fibulin 1 | 22q13.31 | Syndactyly of the third/fourth finger web space and synostosis of the metacarpal and metatarsal bones | |
| SPD3 | 14q11.2-q12 | Third and fourth finger syndactyly with varying degrees of polydactyly of the fourth finger web space. There is also polydactyly of the fifth toe commonly | ||
| SD3 (ODDD spectrum) | Gap Junction Protein Alpha 1 | 6q21-q23.2 | Complete/bilateral, generally soft tissue syndactyly between the fourth and fifth fingers.. The fifth finger is short with absent or rudimentary middle phalanx | |
| SD4/Haas type | LMBR1 | 7q36 | Complete syndactyly, bilateral with polydactyly, generally 6 metacarpals and 6 digits | |
| SD5 | Homeobox D 13 | 2q31-q32 | Soft tissue syndactyly usually affects the 3rd and 4th fingers and 2nd and 3rd toes with associated metatarsal and metacarpal fusion (4th and 5th or the 3rd and 4th) | |
| SD6/Mitten Hand | - | - | Unilateral syndactyly of digits 2-5 | |
| SD7/Cenani-Lenz | LRP4 | 11p11.2 | Severe shortening of the ulna and radius with fusion, fusion of the metacarpals and 'disorganization' of phalangeal development including syndactyly | |
| SD8 | MF4 | ? Xq26 | Fusion of the fourth and fifth metacarpals | |
| SD9/Mesoaxial Synostotic | - | 17p13.3 | completesyndactyly and synostosis of the third and fourth fingers with severe bone reduction in the proximal phalanges, hypoplasia of the thumbs and halluces, aplasia/hypoplasia of the middle phalanges of the second and fifth fingers, and complete or partial soft tissue syndactyly of the toes | |