Metacarpal synostosis | |
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Metacarpal synostosis affecting the fourth and fifth metacarpals of a left hand with thumb hypoplasia type V. | |
Specialty | Medical genetics |
Causes | Genetic mutation |
Frequency | rare, less than 0.07% of the population is born with this trait |
Deaths | - |
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]
There are usually no serious health complications associated with this condition, although severe cases which also involve syndactyly might interfere with hand function.
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]
The following diagnostic methods can be used for metacarpal synostosis: [13]
Treatment for this malformation typically involves the following: [11]
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)
This condition is thought to affect approximately 0.02% to 0.07% of the general population. [14] [15]
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]
Cenani–Lenz syndactylism, also known as Cenani–Lenz syndrome or Cenani–syndactylism, is an autosomal recessive congenital malformation syndrome involving both upper and lower extremities.
Polydactyly or polydactylism, also known as hyperdactyly, is an anomaly in humans and animals resulting in supernumerary fingers and/or toes. Polydactyly is the opposite of oligodactyly.
Apert syndrome is a form of acrocephalosyndactyly, a congenital disorder characterized by malformations of the skull, face, hands and feet. It is classified as a branchial arch syndrome, affecting the first branchial arch, the precursor of the maxilla and mandible. Disturbances in the development of the branchial arches in fetal development create lasting and widespread effects.
Fraser syndrome is an autosomal recessive congenital disorder, identified by several developmental anomalies. Fraser syndrome is named for the geneticist George R. Fraser, who first described the syndrome in 1962.
Carpenter syndrome, also called acrocephalopolysyndactyly type II, is an extremely rare autosomal recessive congenital disorder characterized by craniofacial malformations, obesity, syndactyly, and polydactyly. Acrocephalopolysyndactyly is a variation of acrocephalosyndactyly that presents with polydactyly.
Adams–Oliver syndrome (AOS) is a rare congenital disorder characterized by defects of the scalp and cranium, transverse defects of the limbs, and mottling of the skin.
Abruzzo–Erickson syndrome is an extremely rare disorder characterized by deafness, protruding ears, coloboma, a cleft palate or palatal rugosity, radial synostosis, and short stature. It was first characterized by Abruzzo and Erickson in 1977 as a CHARGE like syndrome as variably expressed among a family of two brothers, their mother, and their maternal uncle. Members of this family exhibited many of the CHARGE symptoms, but notably did not have choanal atresia and the brothers experienced typical genital development. Due to the recent discovery of this disorder, its etiology is not fully known but it is understood that it arises from mutations on the TBX22 gene on the X-chromosome. The disorder is inherited in an X-linked recessive manner. There is currently no known cure but its symptoms can be treated.
Acrocephalosyndactyly is a group of autosomal dominant congenital disorders characterized by craniofacial (craniosynostosis) and hand and foot (syndactyly) abnormalities. When polydactyly is present, the classification is acrocephalopolysyndactyly. Acrocephalosyndactyly is mainly diagnosed postnatally, although prenatal diagnosis is possible if the mutation is known to be within the family genome. Treatment often involves surgery in early childhood to correct for craniosynostosis and syndactyly.
Fibroblast growth factor receptor 2 (FGFR2) also known as CD332 is a protein that in humans is encoded by the FGFR2 gene residing on chromosome 10. FGFR2 is a receptor for fibroblast growth factor.
Antley–Bixler syndrome is a rare, severe autosomal recessive congenital disorder characterized by malformations and deformities affecting the majority of the skeleton and other areas of the body.
EEM syndrome is an autosomal recessive congenital malformation disorder affecting tissues associated with the ectoderm, and also the hands, feet and eyes.
Fibroblast growth factor 16 is a protein which in humans is encoded by the FGF16 gene.
Miller syndrome, also known as Genée–Wiedemann syndrome, Wildervanck–Smith syndrome or postaxial acrofacial dysostosis, is an extremely rare genetic condition that manifests as craniofacial, limb and eye deformities. It is caused by a mutation in the DHODH gene. The incidence of the condition is not known, and nothing is known about its pathogenesis.
Triphalangeal thumb (TPT) is a congenital malformation where the thumb has three phalanges instead of two. The extra phalangeal bone can vary in size from that of a small pebble to a size comparable to the phalanges in non-thumb digits. The true incidence of the condition is unknown, but is estimated at 1:25,000 live births. In about two-thirds of the patients with triphalangeal thumbs, there is a hereditary component. Besides the three phalanges, there can also be other malformations. It was first described by Columbi in 1559.
Ectrodactyly, split hand, or cleft hand involves the deficiency or absence of one or more central digits of the hand or foot and is also known as split hand/split foot malformation (SHFM). The hands and feet of people with ectrodactyly (ectrodactyls) are often described as "claw-like" and may include only the thumb and one finger with similar abnormalities of the feet.
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.
Neu–Laxova syndrome is a rare autosomal recessive disorder characterized by severe intrauterine growth restriction and multiple congenital malformations. Neu–Laxova syndrome is a very severe disorder, leading to stillbirth or death shortly after birth. It was first described by Dr. Richard Neu in 1971 and Dr. Renata Laxova in 1972 as a lethal disorder in siblings with multiple malformations. Neu–Laxova syndrome is an extremely rare disorder with less than 100 cases reported in medical literature.
Filippi syndrome, also known as Syndactyly Type I with Microcephaly and Mental Retardation, is a very rare autosomal recessive genetic disease. Only a very limited number of cases have been reported to date. Filippi Syndrome is associated with diverse symptoms of varying severity across affected individuals, for example malformation of digits, craniofacial abnormalities, intellectual disability, and growth retardation. The diagnosis of Filippi Syndrome can be done through clinical observation, radiography, and genetic testing. Filippi Syndrome cannot be cured directly as of 2022, hence the main focus of treatments is on tackling the symptoms observed on affected individuals. It was first reported in 1985.
Familial opposable triphalangeal thumb duplication is a limb malformation syndrome and a type of pre-axial polydactyly, characterized by having duplicated opposable triphalangeal thumbs. This condition can be a symptom of other genetic disorders, such as Holt–Oram syndrome and Fanconi anemia. This trait is autosomal dominant and often runs in families. Sometimes big toe duplication, post-axial polydactyly, and syndactyly of the hand and feet can occur alongside this malformation Approximately 20 families with the condition have been described in medical literature.
Holoprosencephaly-ectrodactyly-cleft lip/palate syndrome, also simply known as Hartsfield syndrome, is a rare genetic disorder characterized by the presence of variable holoprosencephaly, ectrodactyly, cleft lip and palate, alongside generalized ectodermal abnormalities. Additional findings include endocrine anomalies and developmental delays.