Congenital Contractures
Michael J. Bamshad and John C. Carey
A congenital contracture is broadly defined as a limitation of movement of a body area because of a musculoskeletal abnormality. This abnormality may be caused by a primary or secondary defect of muscle, bone, tendon, or skin, or it may be secondary to impaired neurologic function that causes reduced movement, weakness, and/or hypotonia. Congenital contractures can roughly be distinguished into isolated congenital contractures that affect only a single body area (eg, unilateral or bilateral clubfoot) and multiple congenital contractures that affect two or more different body areas. Individuals with multiple congenital contractures are often diagnosed with arthrogryposis, the literal meaning of which is “twisted joint.” However, arthrogryposis is a description of physical findings and does not imply that the etiology or pathogenesis is similar among affected individuals.
The most common congenital contracture is idiopathic talipes equinovarus (ITEV), or clubfoot, which occurs in 1 in every 200 to 500 live births. Multiple congenital contractures are about 10-fold less common, occurring in about 1 in 3000 to 5000 live births. Worldwide, more than 100,000 children are born each year with a congenital contracture, and it is estimated that more than 5,000,000 people live with congenital contractures. Accordingly, congenital contractures are a substantial source of morbidity.
Most congenital contractures are complex traits, with susceptibility influenced by a heterogenous combination of genetic and environmental factors. Any factor that diminishes movement can, in principle, cause congenital contractures. Examples of such factors include uterine crowding as a result of multiple gestation, oligohydramnios, myotonic dystrophy, and trisomy 18. Indeed, multiple congenital contractures have been observed in more than 300 different conditions.
About 30% of children with multiple congenital contractures are diagnosed with amyoplasia, a phenotype characterized by symmetric reduced muscle bulk of all four limbs and a specific positioning of the limbs with the arms extended and the hips and knees held in flexion. A midfacial capillary hemangioma is also commonly observed. About 10% of affected children have other anomalies, such as gastroschisis or bowel atresia. Most cases are sporadic, but rare families with either multiple affected siblings or an affected parent and child have been reported. The etiology of amyoplasia is unknown but likely to be heterogenous.
Most cases of multiple congenital contractures are sporadic, although autosomal dominant, autosomal recessive, and X-linked inheritance is well documented. The most common of the heritable multiple congenital contracture disorders is a group of about a dozen conditions known as the distal arthrogryposis (DA) syndromes—so called because they predominantly affect the more “distal” joints of the limbs. Features shared among all DAs include a consistent pattern of hand and foot involvement (eg, camptodactyly or flexion contractures of the digits, clubfoot, vertical talus), limited proximal joint involvement, an autosomal dominant inheritance pattern, and variable expressivity.
The most common of the DAs are Freeman-Sheldon syndrome (FSS), Sheldon-Hall syndrome, trismus-pseudocamptodactyly syndrome, and distal arthrogryposis with ophthalmoplegia. In addition to limb contractures, each of these syndromes is also associated with contractures of the facial or oculomotor muscles. For example, in individuals with FSS, facial contractures result in a very small oral orifice, often only a few millimeters in diameter at birth, along with puckered lips, and an H-shaped dimple of the chin. Hence, FSS has also been called whistling face syndrome. The natural history of each of these disorders is different; therefore, distinguishing among them is important. All of these disorders are caused by mutations in one or more genes that encode components of the contractile apparatus of fast-twitch myofibers (eg, myosin, troponin, tropomyosin).
Restricted fetal movement (fetal akinesia or dyskinesia) is sometimes accompanied by marked webbing of the skin (pterygia) across the joints and multiple congenital contractures. Susceptibility to fetal dyskinesia can be influenced by environmental factors such as circulating maternal antibodies against the fetal acetylcholine receptor (AChR) or genetic factors such as mutations in the gene CHRNG, which encodes the fetal subunit of AChR. Heritable disorders characterized by congenital contractures multiple pterygia include Escobar multiple pterygium syndrome (MPS), lethal MPS, and popliteal pterygium syndrome.
In addition to pterygia, children with Escobar type MPS often have short stature, cleft palate, and scoliosis. Most cases appear to have be inherited in an autosomal recessive pattern, although many cases are sporadic. Lethal MPS is characterized by intrauterine growth retardation, polyhydramnios, cystic hygromas, and hy-drops. Often the lungs are hypoplastic and this leads to early death in the neonatal period. Several chondrodysplasias can also present with multiple congenital contractures. These include campomelic dysplasia, Larsen syndrome, Kniest dysplasia, and diastrophic dysplasia.
Children with severe dysfunction of the central nervous system, including those accompanied by structural defects, can also present with multiple congenital contractures. The most common of these include the Pena-Shokeir phenotype and the cerebro-oculo-facial-skeletal (COFS) syndrome. Pena-Shokeir is characterized by a combination of contractures, shortening of the limbs, and pulmonary hypoplasia. At least half a dozen different types have been distinguished by pathological CNS findings. COFS is distinguished by structural abnormalities of the brain, microcephaly, and eye anomalies such as microphthalmia and cataracts. COFS is an autosomal recessive disorder that is caused by mutations in several different genes including ERCC6, the same gene in which mutations that cause Cockayne syndrome type B are found.1-4
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