rare, less than 0.07% of the population is born with this trait
Deaths
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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.[1] Autosomal dominant and X-linked recessive inheritance patterns have been reported.[2][3][4][5][6][7][8]
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.[9]
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.[10]
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.[11]
A syndromic form of syndactyly known as syndactyly type V has metacarpal and metatarsal synostosis as symptoms.[12]
Diagnosis
The following diagnostic methods can be used for metacarpal synostosis:[13]
This condition is thought to affect approximately 0.02% to 0.07% of the general population.[14][15]
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.[16]
↑ Habighorst LV, Albers P (November 1965). "[Familial synostosis of metacarpi IV and V]". Zeitschrift für Orthopädie und Ihre Grenzgebiete. 100 (4): 521–525. PMID4223440.
↑ Lonardo F, Della Monica M, Riccardi G, Riccio I, Riccio V, Scarano G (February 2004). "A family with X-linked recessive fusion of metacarpals IV and V". American Journal of Medical Genetics. Part A. 124A (4): 407–410. doi:10.1002/ajmg.a.20382. PMID14735591. S2CID9168511.
↑ Jamsheer A, Zemojtel T, Kolanczyk M, Stricker S, Hecht J, Krawitz P, etal. (September 2013). "Whole exome sequencing identifies FGF16 nonsense mutations as the cause of X-linked recessive metacarpal 4/5 fusion". Journal of Medical Genetics. 50 (9): 579–584. doi:10.1136/jmedgenet-2013-101659. PMID23709756. S2CID9501794.
↑ Jones B, Byers H, Watson JS, Newman WG (July 2014). "Identification of a novel familial FGF16 mutation in metacarpal 4-5 fusion". Clinical Dysmorphology. 23 (3): 95–97. doi:10.1097/MCD.0000000000000043. PMID24878828.
↑ Annerén G, Amilon A (August 1994). "X-linked recessive fusion of metacarpals IV and V and hypoplastic metacarpal V". American Journal of Medical Genetics. 52 (2): 248–250. doi:10.1002/ajmg.1320520230. PMID7802024.
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