Small Thorax

► [Unusually (often disproportionately) small thoracic cage]

This designation covers a heterogeneous group of disorders characterized both radiographically and clinically by a small thoracic cage. There is significant overlap between this section and that dealing with short ribs. Depending on the degree of the lung volume reduction, subtle abnormalities of the respiratory function or fatal respiratory distress may result. The pathologic counterparts range from small compression atelectases in mild cases to lung hypoplasia in severe cases (Turkel et al. 1985).Altered cardiac hemodynamics is another potential complication of the restricted thorax. A small thoracic cage has been detected prenatally by ultrasound in fetuses with osteogenesis imperfecta type II (Brown 1984), campomel-

Platyspondylic Lethal Skeletal Dysplasia

Fig. 2.1. Platyspondylic lethal skeletal dysplasia (PLSD) or thanatophoric variants, Torrance type. Note small thorax, with short and horizontal ribs; severe platyspondyly; hypoplastic ilia, with trident acetabular appearance; and small, rounded scapulae. Absence of spikes at the inferior scapular border rules out the Luton type of PLSD. (From Mortier et al. 1997)

Fig. 2.1. Platyspondylic lethal skeletal dysplasia (PLSD) or thanatophoric variants, Torrance type. Note small thorax, with short and horizontal ribs; severe platyspondyly; hypoplastic ilia, with trident acetabular appearance; and small, rounded scapulae. Absence of spikes at the inferior scapular border rules out the Luton type of PLSD. (From Mortier et al. 1997)

ic dysplasia (Tongsong et al. 2000),thoracopelvic dysplasia (Hsieh et al. 1999), asphyxiating thoracic dysplasia (Chen et al. 1996), and chondroectodermal dysplasia (Sergi et al. 2001).

A long narrow thorax is typical of thanatophoric dysplasia (OMIM 187600). Both the anteroposterior and lateral diameters are strikingly short, owing to the presence of very short ribs. Cupped costochon-dral junctions and posterior rib scalloping are also present. Additional features include severe platy-spondyly with central end-plate indentations; a characteristic pelvic shape with short and horizontal ilia, small sciatic notch, and short broad ischia and pubic bones; and short, broad, and bowed long bones. The group of disorders referred to as lethal short-limbed platyspondylic dwarfism (OMIM 151210), or thanatophoric dysplasia variants because of their clinical resemblance to classic thanatophoric dysplasia, comprises the Torrance, San Diego, and Luton types. All are perinatally lethal disorders and are characterized by very short extremities, small thorax, large head,

Jeune Syndrome Thoracic Cage
Fig. 2.2. Asphyxiating thoracic dysplasia in a male newborn. Note elongated, narrow thorax, with short ribs and wide anterior ends. Also note handlebar clavicular configuration

short neck, coarse facies, and protuberant abdomen. Radiologic manifestations include decreased ossification of the skull base, small thorax with thin ribs, severe wafer-like platyspondyly, hypoplastic ilia with horizontal acetabula, and short, relatively straight long bones with widened metaphyses (Horton et al. 1979; Winter and Thompson 1982) (Fig. 2.1). Although as a group they can be differentiated from thanatophoric dysplasia, the distinction between types is based mainly on chondro-osseous morphology. However, the particular appearance of the scapula in the Luton type, with two spikes projecting from the inferior scapular border, may assist in the differential diagnosis (Mortier et al. 1997). Thoracic features similar to those of thanatophoric dysplasia, but less severe, occur in homozygous achondroplasia. In achondrogenesis type IA and IB (OMIM 200600, 600972), the thorax is small and barrel-shaped, with short, thin, horizontally oriented ribs, splayed rib ends, and multiple rib fractures (not present in all cases). In achondrogenesis type II (OMIM 200610) the skeletal phenotype is similar, but somewhat milder: the ribs are not as thin, and nor are the long bones so severely shortened and bowed as in type I. Lack of ossification of vertebrae, sacrum, and ischial and pubic bones clearly differentiates achondrogenesis (type I or II) from thanatophoric dwarfism and short rib-polydactyly syndromes. The ribs in hypophos-phatasia, congenital lethal form (OMIM 241500) are short and thin, with unossified ends. Absent ossification of the calvaria, with the exception of some parts of the skull base and facial bones, and large areas of unossified tissue in most of the bones, including the scapulae and iliac bones and the metaphyses of the tubular bones, are distinguishing features. Individuals affected by any of the above conditions are stillborn or die shortly after birth from respiratory failure or intracranial hemorrhage. Asphyxiating thoracic dysplasia,or Jeune syndrome (OMIM 208500), is characterized by a long, narrow thorax in both diameters, with moderately short, horizontal ribs, and irregular, widened costochondral junctions (Fig. 2.2). There are significant interindividual variations in the size of the thorax (Oberklaid et al. 1977). Many cases have a fatal outcome in the newborn period due to pulmonary hypoplasia (Turkel et al. 1985), but instances of mild disease are also known (Giorgi et al. 1990).Affected children surviving beyond the neonatal period manifest a relatively larger thorax and may suffer from recurrent respiratory infections rather than ventilatory insufficiency. Renal and pancreatic symptoms usually become manifest in the longer term survivors. The multisystem nature of this disorder is demonstrated by the presence of periportal fi-brosis, bile duct proliferation, and pancreatic fibrosis in pathological studies (Turkel et al. 1985). The association of small thorax with short ribs, characteristic configuration of the pelvis (small sciatic notches resulting in a heart-shaped pelvic inlet), and a benign course of the respiratory distress in the newborn period occurs in thoracopelvic dysostosis (OMIM 187770). The hands, spine, and skull are normal in this disorder, which is differentiated from asphyxiating thoracic dysplasia on the basis of the benign clinical course, the absence of renal problems, and its seemingly dominant inheritance (Bankier and Danks 1983). Rib shortening of varying degree (from moderate to severe), together with laryngeal stenosis and small pelvis, is a feature in thoraco-laryngo-pelvic dysplasia (Barnes syndrome, OMIM 187760). In the presence of severe rib shortening, lung hypoplasia results in early death. Pathological examination reveals that the laryngeal cartilages are abnormal and the costochondral junctions widely expanded, with histological evidence of 'dystrophic' changes (Barnes et al. 1969). Thoracic dysostosis (OMIM 187750) is a condition with clinical and radiographic manifestations confined to the thorax (Rabushka et al. 1973). Autosomal dominant inheritance is likely. The cardinal features include reduced anterior and posterior diameters of the thoracic cage, with short, irregularly shaped ribs closely resembling those of Melnick-Needles syndrome, and pectus excavatum deformity (Fig. 2.3). The pul

Fig.2.3a,b. Thoracic dysostosis. The anterior ends of the ribs are short, with poorly developed, wavy posterior portions; the upper thorax is constricted, giving the chest cage a bell-shaped configuration. (Reprinted, with permission, from Rabushka et al. 1973)

Ellis Van Creveld Syndrome

Fig.2.3a,b. Thoracic dysostosis. The anterior ends of the ribs are short, with poorly developed, wavy posterior portions; the upper thorax is constricted, giving the chest cage a bell-shaped configuration. (Reprinted, with permission, from Rabushka et al. 1973)

monary function may be adversely affected in this condition. In patients with chondroectodermal dysplasia (Ellis-van Creveld syndrome, OMIM 225500) the thorax is narrow, with short, poorly developed ribs (Fig. 2.4). About one half of the patients die in early infancy of cardiac or respiratory dysfunction. As discussed elsewhere in this book, the pelvic features overlap with those of asphyxiating thoracic dysplasia in early life (Kozlowski et al. 1972). Both thoracic and pelvic changes normalize during childhood. Unlike asphyxiating thoracic dysplasia, hand polydactyly, either pre- or postaxial, is a constant feature in Ellis-van Creveld syndrome. In the presence of polydactyly, differentiation between asphyxiating thoracic dysplasia and Ellis-van Creveld syndrome may be not possible from the radiologic features alone in infancy (Langer 1968). Later in life,hamate-capitate fusion and a characteristic deformity of the proximal tibia (external slanting of the proximal end, with the epiphysis located medially) develop in chon-droectodermal dysplasia. Furthermore, congenital heart defects affect about two-thirds of patients with Ellis-van Creveld syndrome, while renal disease occurs in a large proportion of patients with asphyxiating thoracic dysplasia. Thoracic restriction and poly-dactyly are also prominent features in the short rib-polydactyly syndromes. In short rib-polydactyly syndrome, type I (Saldino-Noonan, OMIM 263530) the ribs are severely short and horizontal, resulting in a small thorax; the tubular bones are unusually short and incompletely ossified, with pointed or ragged ends; hexadactyly is postaxial; and the pelvis is abnormally shaped (small ilia, flattened acetabula with lateral and medial spurs). The thorax is also narrow and constricted with extremely short and horizontal ribs in short rib-polydactyly syndrome, type II (Ma-

jewski, OMIM 263520). The tibia is disproportionately short, hexadactyly can be either pre- or postaxial, and the pelvis is grossly normal, with premature ossification of the proximal femoral epiphyses. In short, pointed metaphyses are the distinguishing features of short rib-polydactyly syndrome type I, while short tibias are characteristic of type II. Infants with either type of short rib-polydactyly syndrome are born dead or die from cardiorespiratory failure within hours or days of birth. Patients with short rib-poly-dactyly syndrome, type III (Verma-Naumoff, OMIM 263510) show changes in the thorax (short and horizontal ribs), skull (short cranial base, bulging forehead, depressed nasal bridge, flat occiput), pelvis (trident appearance), vertebrae (platyspondyly), hands (postaxial polydactyly), and long bones (shortening, widened metaphyses, metaphyseal spurs) (Naumoff et al. 1977; Verma et al. 1975). The assumption that types II and III are distinct disorders has been questioned (Sillence 1980). Moreover, it has been postulated that the short rib-polydactyly syndromes represent a continuous spectrum with variable expressivity rather than separate disorders (Sarafoglou et al. 1999). The familial occurrence of two sibs with mild asphyxiating thoracic dysplasia and a stillborn with short rib-polydactyly syndrome type III has suggested that these conditions could be different manifestations of a single disorder (Ho et al. 2000). Short rib-polydactyly syndrome type III compounded by or overlapping with oro-facio-digital syndrome type II (Mohr syndrome) has also been described (Young et al. 2001) (Fig. 2.5). Cerebro-costo-mandibular syndrome (OMIM 117650), also known as 'rib gap defects with micrognathia' (Miller et al. 1972), is a rare disorder with mental retardation, palatal defects, mi-crognathia, glossoptosis, and severe costovertebral

Fig.2.4a,b. Chondroectoder-mal dysplasia in a 25-week male fetus. a Note narrow, cylindrical thorax with short ribs. b The vertebrae are not affected. (From Sergi et al. 2001)

Fig.2.4a,b. Chondroectoder-mal dysplasia in a 25-week male fetus. a Note narrow, cylindrical thorax with short ribs. b The vertebrae are not affected. (From Sergi et al. 2001)

Cerebro Costo Mandibular Syndrome

Fig. 2.5. a Frontal and b lateral whole-body radiographic images of a stillborn male neonate with short rib-poly-dactyly syndrome type III. Note marked shortening of the ribs, resulting in narrow, elongated thorax. There is also severe shortening of the long bones, with metaphyseal spurs, a trident-shaped pelvis, and platyspondyly. Because this child also had oro-facial and digital anomalies typical of the Mohr syndrome, a diagnosis of compounded SRPS-III and oro-facio-digital syndrome type II (Mohr syndrome) was suggested. (From Young et al. 2001)

Jeune Syndrome Ray

abnormalities. Chest X-ray discloses a small and narrow thorax, with marked hypoplasia of the ribs, and typical gap defects in the posterior arches of the ribs -a clue to the diagnosis. Respiratory distress, gaps of posterior ribs, and micrognathia are virtually constant manifestations. This disorder is usually sporadic, but a few cases of horizontal or vertical transmission are known, suggesting genetic heterogeneity

Kyphomelic Dysplasia
Fig. 2.6. Kyphomelic dysplasia. Note relatively narrow thorax with short, flared ribs; normal scapulae; and short, bowed femurs. (From Mortier et al. 1997)

with autosomal recessive and autosomal dominant inheritance (Plotz et al. 1996). The thoracic cage is also small in campomelic dysplasia (OMIM 114290, 211900), a disorder of the newborn that is characterized by congenital bowing and angulation of long bones (especially the tibias), small scapulae, hy-poplastic and poorly ossified cervical vertebrae,large head, small facies, small hands, and slender clavicles and ribs (Maroteaux et al. 1971). Dislocation of the hips, talipes equinovarus deformities, and 11 pairs of ribs are common features. Most patients die in the neonatal period of respiratory distress resulting either from the small thoracic cage or from narrowed airways secondary to defective tracheobronchial cartilages. Micrognathia, cleft palate, retroglossia, and hypoplastic lungs may further compromise the respiratory function (Houston eta l. 1983). Kyphomelic dysplasia (OMIM 211350) is a short-limb dwarfism characterized by very short angulated femurs and variable bowing of other long bones, with improvement of the bowing during childhood; flared and irregular metaphyses; mild limitation of joint motion; normal cranium and psychomotor development; and moderately short, flared ribs, resulting in a narrow chest and pigeon breast (Fig. 2.6). Disproportionate short stature is a persistent feature. This bent-bone dysplasia is distinguished from campomelic dyspla-sia by the presence in the latter of tibial bowing, hy-poplastic scapulae, mental retardation, and sex reversal (Hall and Spranger 1979; Turnpenny et al. 1990). Atelosteogenesis type II (de la Chapelle syndrome, OMIM 256050) is a lethal short-limb dysplasia consisting of small thorax with short ribs, micromelia predominantly affecting the ulnas and fibulas, bowed long bones, small hands, equinovarus deformity, and cleft palate. Neonatal death may be secondary to pulmonary hypoplasia, laryngeal stenosis, or tracheo-broncho-malacia (Whitley et al. 1986).

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Responses

  • elias
    Have Kyphomelic Dysplasia?
    5 years ago
  • FERUMBRAS
    What disease has bowed tibias and a shortened thorax?
    4 years ago
  • lisa
    Where is the best hospitol for dealing with platyspondylic lethal skeletal dysplasia, Torrance type?
    3 years ago

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