Metacarpal synostosis
{{Infobox medical condition
|name = Metacarpal synostosis
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|caption = Metacarpal synostosis affecting the fourth and fifth metacarpals of a left hand with thumb hypoplasia type V.
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|specialty = Medical genetics
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|causes = Genetic mutation
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|frequency = rare, less than 0.07% of the population is born with this trait
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Metacarpal synostosis is a rare congenital difference which is characterized by the fusion of 2 (or, in rare cases, more) metacarpals of the hand, which are usually shortened. It is most commonly seen as a fusion of the 4th and 5th metacarpals. It is a type of non-syndromic syndactyly/synostosis.{{Cite web |title=Metacarpals 4 and 5 fusion - About the Disease - Genetic and Rare Diseases Information Center |url=https://rarediseases.info.nih.gov/diseases/3559/metacarpals-4-and-5-fusion/ |access-date=2022-06-09 |website=rarediseases.info.nih.gov |language=en}} Autosomal dominant and X-linked recessive inheritance patterns have been reported.{{Cite web |title=OMIM Entry #309630 - Metacarpal 4-5 Fusion; MF4 |url=https://omim.org/entry/309630#1 |access-date=2022-06-09 |website=omim.org |language=en-us}}{{cite journal | vauthors = Habighorst LV, Albers P | title = [Familial synostosis of metacarpi IV and V] | journal = Zeitschrift für Orthopädie und Ihre Grenzgebiete | volume = 100 | issue = 4 | pages = 521–525 | date = November 1965 | pmid = 4223440 | url = https://pubmed.ncbi.nlm.nih.gov/4223440/ }}{{cite journal | vauthors = Lonardo F, Della Monica M, Riccardi G, Riccio I, Riccio V, Scarano G | title = A family with X-linked recessive fusion of metacarpals IV and V | journal = American Journal of Medical Genetics. Part A | volume = 124A | issue = 4 | pages = 407–410 | date = February 2004 | pmid = 14735591 | doi = 10.1002/ajmg.a.20382 | s2cid = 9168511 }}{{cite journal | vauthors = Jamsheer A, Zemojtel T, Kolanczyk M, Stricker S, Hecht J, Krawitz P, Doelken SC, Glazar R, Socha M, Mundlos S | display-authors = 6 | title = Whole exome sequencing identifies FGF16 nonsense mutations as the cause of X-linked recessive metacarpal 4/5 fusion | journal = Journal of Medical Genetics | volume = 50 | issue = 9 | pages = 579–584 | date = September 2013 | pmid = 23709756 | doi = 10.1136/jmedgenet-2013-101659 | s2cid = 9501794 }}{{cite journal | vauthors = Holmes LB, Wolf E, Miettinen OS | title = Metacarpal 4-5 fusion with X-linked recessive inheritance | journal = American Journal of Human Genetics | volume = 24 | issue = 5 | pages = 562–568 | date = September 1972 | pmid = 4538283 | pmc = 1762184 }}{{cite journal | vauthors = Jones B, Byers H, Watson JS, Newman WG | title = Identification of a novel familial FGF16 mutation in metacarpal 4-5 fusion | journal = Clinical Dysmorphology | volume = 23 | issue = 3 | pages = 95–97 | date = July 2014 | pmid = 24878828 | doi = 10.1097/MCD.0000000000000043 }}{{cite journal | vauthors = Annerén G, Amilon A | title = X-linked recessive fusion of metacarpals IV and V and hypoplastic metacarpal V | journal = American Journal of Medical Genetics | volume = 52 | issue = 2 | pages = 248–250 | date = August 1994 | pmid = 7802024 | doi = 10.1002/ajmg.1320520230 }}
Signs and symptoms
The fusion of two or more metacarpal bones is the characteristic feature of this malformation, however this itself causes more symptoms, such as clinodactyly, shortening of the fused metacarpal bones, and reduced range of mobility of the fingers supported by the metacarpals.{{Cite web |title=Kegg Disease: Metacarpal 4-5 fusion |url=https://www.genome.jp/dbget-bin/www_bget?H01854 |access-date=2022-06-09 |website=www.genome.jp}}
Complications
There are usually no serious health complications associated with this condition, although severe cases which also involve syndactyly might interfere with hand function.
Causes
The variant of MS that fuses the 4th and 5th metacarpals is caused by X-linked recessive mutations (alterations or duplications) in the FGF16 gene, in chromosome X.{{cite journal | vauthors = Laurell T, Nilsson D, Hofmeister W, Lindstrand A, Ahituv N, Vandermeer J, Amilon A, Annerén G, Arner M, Pettersson M, Jäntti N, Rosberg HE, Cattini PA, Nordenskjöld A, Mäkitie O, Grigelioniene G, Nordgren A | display-authors = 6 | title = Identification of three novel FGF16 mutations in X-linked recessive fusion of the fourth and fifth metacarpals and possible correlation with heart disease | journal = Molecular Genetics & Genomic Medicine | volume = 2 | issue = 5 | pages = 402–411 | date = September 2014 | pmid = 25333065 | pmc = 4190875 | doi = 10.1002/mgg3.81 }}
It is a feature of various rare disorders such as Apert's syndrome, and can occur alongside other isolated congenital hand/foot malformations including syndactyly, cleft hand, metatarsal synostosis, and polydactyly.{{Cite journal |last1=Buck-Gramcko |first1=Dieter |last2=Wood |first2=Virchel E. |date=1993-07-01 |title=The treatment of metacarpal synostosis |url=https://dx.doi.org/10.1016/0363-5023%2893%2990292-B |journal=The Journal of Hand Surgery |language=en |volume=18 |issue=4 |pages=565–581 |doi=10.1016/0363-5023(93)90292-B |pmid=8394398 |issn=0363-5023|url-access=subscription }}
A syndromic form of syndactyly known as syndactyly type V has metacarpal and metatarsal synostosis as symptoms.{{Cite web |last=RESERVED |first=INSERM US14-- ALL RIGHTS |title=Orphanet: Search a disease |url=https://www.orpha.net/consor/cgi-bin/Disease_Search.php?lng=EN&data_id=12328 |access-date=2022-09-10 |website=www.orpha.net |language=en}}
Diagnosis
The following diagnostic methods can be used for metacarpal synostosis:{{Cite journal |last1=Elalaoui |first1=Siham Chafai |last2=Jdioui |first2=Wafae |last3=Guaoua |first3=Soukaina |last4=Jaouad |first4=Imane Cherkaoui |last5=Madhi |first5=Tarik |last6=Sefiani |first6=Abdelaziz |date=2015-01-06 |title=Report of the First Moroccan Case of Fusion of Metacarpals 4/5 and Review of the Literature |url=https://theijcp.org/index.php/ijcp/article/view/186 |journal=International Journal of Clinical Pediatrics |language=en |volume=3 |issue=4 |pages=117–120|doi=10.14740/ijcp176e |doi-access=free }}
Treatment
Treatment for this malformation typically involves the following:
1. Osteotomy (for splitting/separating the synostosic metacarpals)
2. Bone graft (for lengthening of shortened metacarpals, usually the fifth)
3. Ligament reconstruction
4. Tendon transposition (for the extensor digiti minimi quinti)
Epidemiology
This condition is thought to affect approximately 0.02% to 0.07% of the general population.{{cite journal | vauthors = Liao CD, Yamin F, Simpson RL | title = Correction of 4th and 5th metacarpal synostosis in a skeletally mature hand using de-rotational osteotomies | journal = Case Reports in Plastic Surgery & Hand Surgery | volume = 9 | issue = 1 | pages = 15–21 | date = 2022-12-31 | pmid = 34993272 | pmc = 8725938 | doi = 10.1080/23320885.2021.2011290 }}{{cite journal | vauthors = Gottschalk MB, Danilevich M, Gottschalk HP | title = Carpal Coalitions and Metacarpal Synostoses: A Review | journal = Hand | volume = 11 | issue = 3 | pages = 271–277 | date = September 2016 | pmid = 27698627 | pmc = 5030847 | doi = 10.1177/1558944715614860 }}
Associations
A large family has been described as having nonsense mutations of the FGF16 gene which resulted in metacarpal synostosis and, unexpectedly, in heart disease.{{cite journal | vauthors = Laurell T, Nilsson D, Hofmeister W, Lindstrand A, Ahituv N, Vandermeer J, Amilon A, Annerén G, Arner M, Pettersson M, Jäntti N, Rosberg HE, Cattini PA, Nordenskjöld A, Mäkitie O, Grigelioniene G, Nordgren A | display-authors = 6 | title = Identification of three novel FGF16 mutations in X-linked recessive fusion of the fourth and fifth metacarpals and possible correlation with heart disease | journal = Molecular Genetics & Genomic Medicine | volume = 2 | issue = 5 | pages = 402–411 | date = September 2014 | pmid = 25333065 | pmc = 4190875 | doi = 10.1002/mgg3.81 }}
== References ==
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