Radial Ray Deficiency

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► [Hypoplasia or aplasia involving the radius, the radially placed carpals (scaphoid, trapezium and trapezoid), and the thumb]

Radial ray deficiency is a relatively common defect, which can be isolated, associated with other congenital malformations, or occur in the context of distinct syndromes. The defect is either unilateral or bilateral. When bilateral, it can vary in the degrees of severity on the two sides. Bilateral involvement is characteristic of the syndromic disorders, whereas the unilateral distribution occurs most typically with the isolated form and nonsyndromic associations.

Isolated radial defects are sporadic in most cases. Varying degrees of reduction are found, from mild hypoplasia of the thumb to partial or total aplasia of the radius and thumb. When the radius is totally aplastic, the thumb, scaphoid, and trapezium are also usually absent. Moreover, the ulna is frequently curved, and the hand is radially deviated and clubbed. The forearm is invariably shortened, while shortening of the entire arm is observed in only one third of cases (Heikel 1959). When the radius is hypoplastic the thumb can be either hypoplastic or absent. With thumb hypoplasia there is usually some hypoplasia of the 1st metacarpal. If the thumb is absent, the scaphoid and trapezium are invariably also absent. Carpal fusion and anomalies of carpals other than those located on the radial side are also sometimes seen. Impaired function at the elbow and wrist, with fixed extension contracture or deficit of active motion, is common, and usually correlates with the severity of the radial ray defect.

A significant number of patients with radial ray deficiency have some associated anomalies.Congeni-tal heart defects,especially ventricular and atrial sep-tal defects, pulmonary artery atresia, and patent duc-tus arteriosus, are the most common, followed by spina bifida, cleft palate, Klippel-Feil deformity, and brain and renal anomalies. Radial hypoplasia can also occur in association with polydactyly, syndactyly, and triphalangism (Birch-Jensen 1949). The commonest and best known of these associations is the VATER association (OMIM 192350), an acronym for vertebral defects (70%), anal atresia (80%), tracheoesophageal fistula (70%), esophageal atresia (70%), and radial limb anomalies (65%) (Quan and Smith 1972). The spectrum of developmental anomalies has been further expanded by the inclusion of cardiac malformations, renal anomalies, and more complex limb anomalies (preaxial polydactyly, humeral hypoplasia, radial aplasia, and proximally placed thumb) and is designated as VACTERL, an acronym now used interchangeably with VATER (Khoury et al. 1983). Nearly all recorded cases have been sporadic, and no teratogen or chromosomal abnormality has been recognized. Defective sonic hedgehog (SHH) signaling leads to a spectrum of anomalies in mice almost identical to those of the VACTERL association (Kim et al. 2001). Familial VACTERL with hydrocephalus (OMIM 314390) is recognized as a separate X-linked disorder (Sujansky and Leonard 1983; Briard et al. 1984). In addition to the anomalies typical of VACTERL, other features include ear malformation, dolichocephaly, cleft palate, retrognathia, incomplete lung lobation, pancreas agenesis, and internal hydrocephalus with cortical dysplasia and agenesis of the corpus callosum (Froster et al. 1996). A form of VACTERL association with hydrocephalus and an autosomal recessive mode of inheritance is also possible (OMIM 276950). Radial aplasia, X-linked (OMIM 312190) is an association of bilateral absence of radius and anogenital anomalies (hypospadias, imperforate anus) (Gibson et al. 1993). Radial ray deficiency, X-linked (OMIM 300378) is a distinct disorder characterized by bilateral radial aplasia, broad curved ulnas, hypoplasia of the thumbs, and some additional anomalies, including Dandy-Walker malformation, transposition of the great arteries, and atrial septal defect. It is possible that the gene responsible, which is located on chromosome X,is involved in patterning, differentiation, or apoptosis during human embryonic limb development (Galjard et al. 2001). In the rare condition termed mirror-image polydactyly (duplication of ulna and fibula/absence of radius and tibia, OMIM 135750), bilateral absence of the radius and tibia is associated with bilateral duplication of the ulna and fibula and polysyndactyly (Sandrow et al. 1970). Abnormalities of the nose, consisting in hypoplastic nasal alae and a deep groove in the columella, are also peculiar to the condition (Martin et al. 1993). Additional findings can include oversized mandibular condyles, brachymesophalangy of toes, mental retardation, triphalangeal thumbs, and tarsal synos-tosis (Kantaputra 2001). The mirror hand has been regarded as a defect of differentiation of a part of the ray (Chinegwundoh et al. 1997). Disruption of a gene involved in anteroposterior patterning of the limbs in early development has been implicated (Kim et al. 1997), and a translocation breakpoint has been localized at 14q13 (Matsumoto et al. 1997). Another association, consisting of severe dilatation of the lateral cerebral ventricles, bilateral aplasia of the radii and

Radial Ray Deficiency

Fig. 6.14. Goldenhar complex in a female newborn. Note radial aplasia and oligodactyly with absent thumb. The hand is radially deviated. The entire left upper limb was short, with hy-poplasia of humerus and scapula. The right arm was normal. Such limb defects as that shown here occur only occasionally in Goldenhar syndrome. (Reprinted, with permission, from Zelante et al. 1997)

Fig. 6.14. Goldenhar complex in a female newborn. Note radial aplasia and oligodactyly with absent thumb. The hand is radially deviated. The entire left upper limb was short, with hy-poplasia of humerus and scapula. The right arm was normal. Such limb defects as that shown here occur only occasionally in Goldenhar syndrome. (Reprinted, with permission, from Zelante et al. 1997)

Hypoplastic Thumb
Fig. 6.15. Fanconi anemia in the same male newborn as shown in Part 2, Fig. 45.4. Note absent radius and thumb on the left side, and mild radial hypoplasia with severe thumb hypoplasia on the right. Both hands are clubbed

thumbs, and kidney malformation, has been found in two consecutive mid-trimester fetuses (ventricu-lomegaly with defects of the radius and kidney, OMIM 602200). In one fetus there was an ectopic horseshoe kidney,while in the other the right kidney was absent (Kovacs et al. 1997). In two further, unrelated, families, radial aplasia/hypoplasia and absent thumbs and index fingers were associated with conductive deafness, external ear deformity, dysmorphic face (maxillary hypoplasia, long philtrum), and sinus arrhythmia (phocomelia-ectrodactyly, ear malformation, deafness, and sinus arrhythmia, OMIM 171480) (Stoll et al. 1974; Harding et al. 1982).

Several inherited syndromes display varying degrees of radial deficiency (Fig. 6.14). Although many of these disorders have been discussed in more detail elsewhere in this book, some are briefly reviewed in this section. Fanconi anemia (Fanconi pancytopenia syndrome, OMIM 227650, 227660, 227645, 227646, 600901) is an autosomal recessive, genetically heterogeneous disorder affecting the bone marrow (anemia, leukopenia, and thrombocytopenia), the kidneys, the skin, and the limbs (Fanconi 1927). The disorder involves marked variability of the clinical phenotype, one third of affected individuals lacking congenital malformations and the remainder displaying a variable combination of dysmorphic features. In addition to short stature, brownish pigmentation (65%), radial-ray (50%) and renal (35%) malformations, affected patients can present with cardiac (13%), gastrointestinal (14%), central nervous system (8 %), genital (20 % in males), and various other, skeletal, abnormalities (22%) (Giampietro et al. 1993). Radial ray abnormalities range from bilateral absence of radii and thumbs to a unilateral hypoplastic or bifid thumb (Figs. 6.15, 6.16). Bilateral absence of radii with thumbs present and a blood disorder selectively involving the platelets (mega-karyocyte growth defect) are cardinal features of the thrombocytopenia-absent radius syndrome (TAR, OMIM 274000), a rare autosomal recessive disorder. In contrast to Fanconi pancytopenia syndrome, neither hypoplasia of the erythron nor involvement of the thumbs or skin occurs in this disorder (Shaw and Oliver 1959; Hall et al. 1969). The presence of the radial artery - albeit with an abnormal course - indicates that radial aplasia is a primary defect, a point of difference from other disorders, in which radial apla-sia is secondary to failure of the blood supply (van Allen et al. 1982). Thrombocytopenia is usually symptomatic in early life, but is transient. Heart disease and renal malformations are occasionally encountered. Cleft lip and palate are rare and, when present in a child with bilateral radial aplasia, must suggest the diagnosis of Roberts syndrome (SC pho-comelia syndrome, OMIM 268300). Abnormalities in the legs are frequent (Ray et al. 1980). The most severe expression of the disease in the limbs, tetrapho-comelia, may simulate thalidomide embryopathy (Anyane-Yeboa et al. 1985). In thalidomide embryopathy, the degree of limb involvement ranges from mild hypoplasia of the 1st metacarpal to severe limb reduction deformities, including phocomelia and complete four-limb amelia. The preaxial bones and the upper extremities are the most commonly involved (McBride 1977). Similarly, the range of up-

Female Clubbed Thumb
Fig. 6.16. Fanconi anemia in a woman patient. Note absence of radius and radially placed carpals (scaphoid and trapezium) and thumb. The ulna is abnormally short and curved, and the hand is clubbed

per limb involvement (varying degrees of hypoplasia/aplasia of humerus,radius, thumb and carpals) in Holt-Oram syndrome (OMIM 142900) is broad, and it can be sufficiently severe to simulate thalidomide effect. However, the characteristic findings in the disease are thumb anomaly and atrial septal defect (Penne et al. 1997). The thumb can be absent or be a triphalangeal, fingerlike digit. Extra carpal bones are also highly characteristic for the disease (Poznanski et al. 1970). The involvement of the arms is bilateral but not symmetrical. In Baller-Gerold syndrome (OMIM 218600) radial defects occur in association with craniosynostosis (metopic, sagittal, and coronal synostosis) (Baller 1950; Gerold 1959). This pheno-type overlaps with those of several other disorders, including Fanconi anemia, Roberts syndrome, VAC-TERL association with hydrocephalus, and Saethre-Chotzen syndrome (Farrell et al. 1994; Huson et al. 1990; Toriello et al. 1991; Gripp et al. 1999). Given the well-known clinical heterogeneity of Fanconi anemia, the question has been raised as to whether the Baller-Gerold syndrome is a separate disorder or a phenotypic variant of Fanconi anemia (Cohen and Toriello 1996). Reports raising such questions have also led to a new and narrower definition of BallerGerold syndrome, based on the exclusion of cyto-genetic (premature centromere separation is characteristic of the Roberts syndrome, chromosome breakage of Fanconi anemia) and hematopoietic abnormalities. The radial deficiency can be symmetrical or asymmetrical, and the ulna is always short and curved.Variable degrees of hypoplasia/aplasia of the thumbs and carpals are observed. Cases of BallerGerold syndrome can be divided into those with craniosynostosis and radial defects alone and those with a broad range of additional malformations (Galea and Tolmie 1990). Facultative manifestations include conductive hearing loss, skeletal and heart anomalies, imperforate anus, rectovaginal fistula, prenatal growth deficiency, and mental and/or motor retardation (Pelias et al. 1981; Dallapiccola et al. 1992). Steinfeld syndrome (OMIM 184705), an autosomal dominant condition with variable expression, comprises holoprosencephaly, bilateral hypoplasia of the radius and ulna, absent thumbs, cleft lip and palate, congenital heart defect, unilateral renal dysplasia, and absent gallbladder (Steinfeld 1982). Rothmund-Thomson syndrome (OMIM 268400) is a rare, hereditary cancer-prone genodermatosis characterized by skin atrophy, pigmentation, and telangiecta-sia and is frequently accompanied by juvenile cataract, saddle nose, congenital bone defects, disturbances of hair growth, and hypogonadism. Various skeletal anomalies have been described, including short hands and feet, radial deficiency with thumb hypoplasia/aplasia, syndactyly, brachyphalangy, split hand, bowed long bones, and osteoporosis. Resorption of the phalangeal tufts, dystrophic calcifications, platyspondyly, and retarded bone age are additional features that can be encountered (Maurer and Langford 1967; Starr et al. 1985; Hall et al. 1980).

Occasionally, in the presence of a single bone in the forearm, there can be some uncertainty as to whether this bone is the ulna or the radius. This is so in microcephaly-micromelia syndrome (Ives-Hous-ton syndrome, OMIM 251230), an autosomal recessive disorder in which a single bone - without further specification - was described in the markedly shortened forearms of affected babies in the original report (Ives and Houston 1980). The hands were abnormal with only two to four malformed digits, and the elbows were fused. Intrauterine growth retardation, perinatal death, and marked microcephaly were also reported.

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