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

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