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Polysyndactyly

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Polysyndactyly is a congenital anomaly, combining polydactyly and syndactyly, in which affected individuals have an extra finger or toe that is connected, via fusing or webbing, to an adjacent digit.[1][2]

Signs and Symptoms

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Presentations of polysyndactyly vary in location and size of the duplicated digit, and in the extent of webbing between digits [3][2][4].

The extra digit is most commonly postaxial[5], on the same side as the pinky or little toe.[3] Preaxial polysyndactyly, in which the duplicated digit is on the side of the thumb or big toe, is less common[3]. Crossed polysyndactyly, in which polysyndactyly is present on the hand and foot, and is preaxial on one and postaxial on the other, is extremely rare and often occurs with other genetic disorders.[6]

Polysyndactyly may be classified by the level of duplication. The extra digit may be small and comprise only soft tissue[7], but usually includes at least one bone, most commonly the distal and middle phalanges[8][9]. Partial or complete duplication of the proximal phalanx, metacarpal or metatarsal can also occur[7][8].

Fusing of the extra digit may be incomplete[4], giving the appearance of the extra digit being partially connected to the (otherwise normal) digit next to it. However, complete fusion of the extra digit to the adjacent digit, via soft tissue and skin, is more common.[4]

Causes

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Polysyndactyly is typically inherited, in an autosomal dominant pattern[10][6][2]. The specific mutations leading to polysyndactyly are varied between among types of the condition and different families. However, many cases are caused by changes to genetic elements affecting the signaling molecule Sonic Hedgehog (SHH). Primarily, mutations are found in the zone of polarizing activity regulatory sequence, or ZRS, that controls the expression of SHH in developing limbs. Many cases of polysyndactyly are the result of duplications of the ZRS[11][12][13] or the nearby pre-ZRS region.[14][15]

Polysyndactyly can be associated with the presence of other genetic disorders. It is a hallmark of Carpenter's syndrome, an autosomal recessive disorder that is also associated with craniosynostosis, obesity, short stature, and other malformations[16]. Patients with other syndromes, including those with Pallister-Hall syndrome[17] and Greig cephalopolysyndactyly syndrome[18] may also display polysyndactyly of varying severity.

Polysyndactyly has full penetrance but variable expressivity. This means that individuals possess an allele for polysyndactyly, but may have a different severity of polysyndactyly. This has been seen in case studies where a parent has hexadactyly in their 4th and 5th fingers but their child has hexadactyly in their 1st, 2nd, 3rd and 4th fingers.[19]

Diagnosis

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Polysyndactyly can be diagnosed in utero through sonographic and genetic testing, though sonography may be preferred due to the cost and risk associated with genetic testing[20]. Ultrasounds, typically done at the 14th to 16th week of pregnancy, can detect the presence of extra metacarpals, metatarsals, or phalanges[20][21]. Genetic testing of the fetus examines disruptions in the HOXD13 gene at 2q31-q32 and in the GLI3 gene at 7p13. These genomic regions regulate proliferation and differentiation in the limb bud, and can lead to phenotypic anomalies, including polysyndactyly, if mutated. Postnatally, polysyndactyly is diagnosed by observation of an extra digit and X-rays to confirm the presence of an extra metacarpal, metatarsal, or phalanx.[20][22]

Treatment and Prognosis

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Polysyndactyly is treated through surgical excision of the extra digit. The choice of which digit to remove affects post-operative outcomes; factors that must be considered when determining which digit to excise include the neurovascular bundles, angle differences, risks for impaired circulation, post-operative appearance, and residual deformities.[5][7]

Treatment is generally aimed at normalizing both function and appearance of the affected extremity[3] and, in the case of polysyndactyly of the foot, shoe fit and comfort[23]. The underlying cause of polysyndactyly determines the overall quality of life for individuals diagnosed with this condition. If there are no comorbid or underlying genetic conditions, surgical removal of the extra digit generally results in a high quality of life. Parents of children with polysyndactyly have reported high physical, social, emotional, and school functioning and good psychosocial health after removal of the extra digit.[24]

References

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  1. ^ Lica, L. (2020). "Polydactyly and Syndactyly". In Longe, J.L. (ed.). Gale Encyclopedia of Medicine (6th ed.). Gale.
  2. ^ a b c Holmes, Lewis B. (2011-10). "Limb Malformations". Common Malformations. Oxford University Press. doi:10.1093/med/9780195136029.003.0015,. ISBN 978-0-19-513602-9. {{cite book}}: Check |doi= value (help); Check date values in: |date= (help)CS1 maint: extra punctuation (link)
  3. ^ a b c d Stevenson, Roger E. (2015). Human Malformations and Related Anomalies. Judith G. Hall, David B. Everman. Cary: Oxford University Press. ISBN 978-0-19-938604-8. OCLC 936298415.
  4. ^ a b c Chen, Wei; Chen, Lu; Huang, Wei; Tian, Xiaofei (2021-03). "Aesthetic and Anatomic Reconstruction of Polysyndactyly of the Fifth Toe Fused With the Fourth Toe". Annals of Plastic Surgery. 86 (3): 323–328. doi:10.1097/SAP.0000000000002437. ISSN 1536-3708. {{cite journal}}: Check date values in: |date= (help)
  5. ^ a b Ko, Kyung Rae; Shim, Jong Sup; Kang, Jiwon; Park, Jaesung (2021-05). "Surgical Outcomes and Predictive Factors of Medial Toe Excision for Polysyndactyly of the Fifth Toe". Foot & Ankle International. 42 (5): 562–569. doi:10.1177/1071100720971289. ISSN 1071-1007. {{cite journal}}: Check date values in: |date= (help)
  6. ^ a b Dewan, Pooja; Agarwal, Nitin; Dewan, Preeti; Batta, Vineet (2010-05). "Familial crossed polysyndactyly in four generations of an Indian family". World Journal of Pediatrics. 6 (2): 177–180. doi:10.1007/s12519-010-0020-7. ISSN 1708-8569. {{cite journal}}: Check date values in: |date= (help)
  7. ^ a b c Woo, Soo Jin; Kim, Byung Jun; Kwon, Sung Tack (2021-01). "Case-control study of the treatment of postaxial polysyndactyly of the foot: Comparison of surgical results after removal of the fifth or sixth toe". Archives of Plastic Surgery. 48 (01): 91–97. doi:10.5999/aps.2020.01620. ISSN 2234-6163. PMC 7861990. PMID 33503751. {{cite journal}}: Check date values in: |date= (help)CS1 maint: PMC format (link)
  8. ^ a b Chen, Wei; Chen, Lu; Huang, Wei; Tian, Xiaofei (2021-03). "Aesthetic and Anatomic Reconstruction of Polysyndactyly of the Fifth Toe Fused With the Fourth Toe". Annals of Plastic Surgery. 86 (3): 323–328. doi:10.1097/SAP.0000000000002437. ISSN 1536-3708. {{cite journal}}: Check date values in: |date= (help)
  9. ^ Bae, Kunhyung; Kang, Michael Seungcheol; Kim, Tae Hyung; Park, Soo-Sung (2021-05-13). "Classification of Middle Phalangeal Postaxial Polysyndactyly Based on Intraoperative Arthrography Is Useful for Surgical Decision-making in Children Younger Than 2 Years". Journal of Pediatric Orthopaedics. Publish Ahead of Print. doi:10.1097/BPO.0000000000001858. ISSN 0271-6798.
  10. ^ Temtamy, Samia A. (1985-03). "The Genetics of Hand Malformations: Updated". Congenital Anomalies. 25 (1): 73–92. doi:10.1111/j.1741-4520.1985.tb00636.x. ISSN 0914-3505. {{cite journal}}: Check date values in: |date= (help)
  11. ^ Xu, Jihai; Wu, Jing; Teng, Xiaofeng; Cai, Libing; Yuan, Huizong; Chen, Xiaokun; Hu, Mu; Wang, Xin; Jiang, Ning; Chen, Hong (2020-09). "Large duplication in LMBR1 gene in a large Chinese pedigree with triphalangeal thumb polysyndactyly syndrome". American Journal of Medical Genetics Part A. 182 (9): 2117–2123. doi:10.1002/ajmg.a.61757. ISSN 1552-4825. {{cite journal}}: Check date values in: |date= (help)
  12. ^ Lohan, S.; Spielmann, M.; Doelken, S.C.; Flöttmann, R.; Muhammad, F.; Baig, S.M.; Wajid, M.; Hülsemann, W.; Habenicht, R.; Kjaer, K.W.; Patil, S.J.; Girisha, K.M.; Abarca-Barriga, H.H.; Mundlos, S.; Klopocki, E. (2014-10). "Microduplications encompassing the Sonic hedgehog limb enhancer ZRS are associated with Haas-type polysyndactyly and Laurin-Sandrow syndrome: Microduplications encompassing the Sonic hedgehog limb enhancer". Clinical Genetics. 86 (4): 318–325. doi:10.1111/cge.12352. {{cite journal}}: Check date values in: |date= (help)
  13. ^ Dai, Limeng; Guo, Hong; Meng, Hui; Zhang, Kun; Hu, Hua; Yao, Hong; Bai, Yun (2013-11). "Confirmation of genetic homogeneity of syndactyly type IV and triphalangeal thumb–polysyndactyly syndrome in a Chinese family and review of the literature". European Journal of Pediatrics. 172 (11): 1467–1473. doi:10.1007/s00431-013-2071-y. ISSN 0340-6199. {{cite journal}}: Check date values in: |date= (help)
  14. ^ Potuijt, Jacob W.P.; Baas, Martijn; Sukenik-Halevy, Rivka; Douben, Hannie; Nguyen, Picard; Venter, Deon J.; Gallagher, Renée; Swagemakers, Sigrid M.; Hovius, Steven E.R.; van Nieuwenhoven, Christianne A.; Galjaard, Robert-Jan H.; van der Spek, Peter J.; Ahituv, Nadav; de Klein, Annelies (2018-11). "A point mutation in the pre-ZRS disrupts sonic hedgehog expression in the limb bud and results in triphalangeal thumb–polysyndactyly syndrome". Genetics in Medicine. 20 (11): 1405–1413. doi:10.1038/gim.2018.18. {{cite journal}}: Check date values in: |date= (help)
  15. ^ Potuijt, Jacob W. P.; Sowinska-Seidler, Anna; Bukowska-Olech, Ewelina; Nguyen, Picard; Jankowski, Aleksander; Magielsen, Frank; Matuszewska, Karolina; van Nieuwenhoven, Christianne A.; Galjaard, Robert-Jan H.; de Klein, Annelies; Jamsheer, Aleksander (2022-09). "The pZRS non-coding regulatory mutation resulting in triphalangeal thumb–polysyndactyly syndrome changes the pattern of local interactions". Molecular Genetics and Genomics. 297 (5): 1343–1352. doi:10.1007/s00438-022-01921-2. ISSN 1617-4615. {{cite journal}}: Check date values in: |date= (help)
  16. ^ Temtamy, Samia A. (1966-07). "Carpenter's syndrome: Acrocephalopolysyndactyly. An autosomal recessive syndrome". The Journal of Pediatrics. 69 (1): 111–120. doi:10.1016/S0022-3476(66)80368-2. {{cite journal}}: Check date values in: |date= (help)
  17. ^ Consales, Alessandra; Ardemani, Giulia; Cinnante, Claudia Maria; Catalano, Mariana Rita; Giavoli, Claudia; Villa, Roberta; Iascone, Maria; Fontana, Camilla; Bedeschi, Maria Francesca; Fumagalli, Monica (2022-12). "Neuroimaging appearance of hypothalamic hamartomas in monozygotic twins with Pallister-Hall syndrome: case report and review of the literature". BMC Neurology. 22 (1): 118. doi:10.1186/s12883-022-02618-0. ISSN 1471-2377. PMC 8943937. PMID 35331151. {{cite journal}}: Check date values in: |date= (help)CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link)
  18. ^ Biesecker, Leslie G (2008-12). "The Greig cephalopolysyndactyly syndrome". Orphanet Journal of Rare Diseases. 3 (1): 10. doi:10.1186/1750-1172-3-10. ISSN 1750-1172. PMC 2397380. PMID 18435847. {{cite journal}}: Check date values in: |date= (help)CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link)
  19. ^ Fried, K.; Mundel, G. (1974-06-01). "Polysyndactyly and Marfan's syndrome". Journal of Medical Genetics. 11 (2): 141–144. doi:10.1136/jmg.11.2.141. ISSN 1468-6244. PMC 1013109. PMID 4366482.{{cite journal}}: CS1 maint: PMC format (link)
  20. ^ a b c Zhang, Shi-Jie; Lin, Hai-Bin; Jiang, Qiu-Xia; He, Shao-Zheng; Lyu, Guo-Rong (2021-08-16). "Prenatal diagnosis of triphalangeal thumb-polysyndactyly syndrome by ultrasonography combined with genetic testing: A case report". World Journal of Clinical Cases. 9 (23): 6832–6838. doi:10.12998/wjcc.v9.i23.6832. ISSN 2307-8960. PMC 8362503. PMID 34447832.{{cite journal}}: CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link)
  21. ^ Zimmer, Etan Z.; Bronshtein, Moshe (2000-09-01). "Fetal polydactyly diagnosis during early pregnancy: Clinical applications". American Journal of Obstetrics & Gynecology. 183 (3): 755–758. doi:10.1067/mob.2000.106974. ISSN 0002-9378.
  22. ^ Rédei, George P., ed. (2008), "Polysyndactyly", Encyclopedia of Genetics, Genomics, Proteomics and Informatics, Dordrecht: Springer Netherlands, pp. 1535–1535, doi:10.1007/978-1-4020-6754-9_13251, ISBN 978-1-4020-6754-9, retrieved 2022-11-06
  23. ^ Burger, Elise; ‘t Hart, Judith; Hovius, Steven; Van Nieuwenhoven, Christianne (2022-09-20). "Quality of life in children with preaxial polydactyly of the foot in comparison to adults, postaxial polydactyly and healthy controls". Journal of Pediatric Orthopaedics B. Publish Ahead of Print. doi:10.1097/BPB.0000000000001004. ISSN 1060-152X.
  24. ^ Gao, Qisheng; Wang, Shanshan; Ren, Jianping; Wen, Xin (2020-12). "Measuring parent proxy-reported quality of life of 11 rare diseases in children in Zhejiang, China". Health and Quality of Life Outcomes. 18 (1): 372. doi:10.1186/s12955-020-01572-0. ISSN 1477-7525. PMC 7682005. PMID 33225969. {{cite journal}}: Check date values in: |date= (help)CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link)
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