Fig. 2.22. Craniodiaphyseal dysplasia in a 3-year-old boy. Ribs and clavicles are expanded and flattened
Many of the conditions with broad ribs also display broad tubular bones, a subject discussed elsewhere in this book. Accordingly, these two topics share similarities with regard to the mechanisms involved in the expansion of the bones, the origin of the defect, whether it is congenital or acquired, and its distribution (focal or diffuse). The discussion of this topic also overlaps with that covering cortical thickening of the tubular bones. The reader is referred to Chapter 5
Fig. 2.22. Craniodiaphyseal dysplasia in a 3-year-old boy. Ribs and clavicles are expanded and flattened for a thoroughgoing discussion of individual disorders. Some aspects related to the location of specific lesions within the ribs are addressed in this section.
Marked expansion of the ribs and clavicles reflecting a severe tubulation defect, together with Erlenmeyer flask deformities about the metaphyses of the long bones and mild cranial sclerosis, occurs in metaphyseal dysplasia (Pyle disease, OMIM 265900) (Heselson et al. 1979). Craniodiaphyseal dysplasia (OMIM 218400), a condition with progressive thickening and distortion of the facies (leontiasis ossea) and marked sclerosis of the skull, facial bones, and mandible, shows wide, flat ribs and clavicles (Fig. 2.22). Uniformly widened tubular bones, with thin cortices and lack of normal flaring of the meta-physes (tubulation defect) are characteristic of this disorder (Macpherson 1974; Brueton and Winter 1990). In pachydermoperiostosis (OMIM 167100), an autosomal dominant disorder affecting adolescents and progressing throughout adulthood, the ribs are wide, with sclerotic islands and coarse trabeculae. Cortical thickening and sclerosis occurs about the calvaria, skull base, clavicles, and tubular bones, sometimes resulting in diaphyseal expansion. The ungual tufts are prominent due to periosteal hyper-ostosis. Occasionally, resorption of distal phalanges of hands and feet occurs. Bone trabeculation is coarse, with dense sclerotic bands crossing the spon-giosa and arranged along pressure and traction lines (in the vertebrae, these dense striae parallel the superior and inferior end plate; in the hands, they may run along the distal end of the metacarpals and proximal end of the phalanges). Clinically the condition is characterized by clubbing of fingers and toes, disproportionately long extremities, joint discomfort, and de
Fig. 2.24 a, b. Hurler syndrome. a In a 4-month-old baby boy. Note characteristic widening of the lateral and anterior rib segments (arrows), and relative narrowing of the posterior portions. b In a 5-year-old boy. The ribs are wide anteriorly and laterally, and are overconstricted in their paravertebral portions velopment of coarse, thick, oily skin of the hands, feet, and upper face and scalp,resulting in cutis verticis gy-rata (Rimoin 1965; Polat and Suma 1999; Spranger et al. 1974). In oculo-dento-osseous dysplasia (oculodentodigital syndrome, OMIM 164200, 257850) the ribs are slightly enlarged,whereas the clavicles show a significant expansion of their medial portions (Reisner et al. 1969; Thoden et al. 1977). Cortical hyperostosis typical of Caffey's disease (OMIM 114000) may involve one or more ribs, the mandible, clavicles, scapulae, and long bones (Fig. 2.23).
A specific type of rib widening is seen almost exclusively in storage diseases, consisting in marked narrowing of the ribs posteriorly and considerable broadening laterally and anteriorly. This aspect is typically seen in mucopolysaccharidosis type I-H (Hurler, OMIM 252800) and type IV (Morquio, OMIM 253000) (Fig. 2.24 a,b). A coarse trabecular pattern is seen throughout the ribs. The clavicles are short and thick. Broadening and prominent trabecu-lation of the ribs also occur in mucopolysaccharidosis type I-S (Scheie, OMIM 252800), and type VI (Maro-teaux-Lamy, OMIM 253000). In type II (Hunter, OMIM 309900) these features are less prominent. In type III (Sanfilippo, OMIM 252900) widening is striking about the clavicles and less constant and severe about the ribs. In mucopolysaccharidosis type VII (Sly syndrome, OMIM 253220) widening of the ribs, with flaring of the lower ribs, and prominent sternum are seen. In mucolipidosis I (OMIM 256550) the ribs are
Fig. 2.24 a, b. Hurler syndrome. a In a 4-month-old baby boy. Note characteristic widening of the lateral and anterior rib segments (arrows), and relative narrowing of the posterior portions. b In a 5-year-old boy. The ribs are wide anteriorly and laterally, and are overconstricted in their paravertebral portions slightly expanded, while in mucolipidosis II (I-cell disease, OMIM 252500) and III (pseudo-Hurler poly-dystrophy, OMIM 252600) the ribs are similar to those of Hurler syndrome, that is, posteriorly constricted, with marked expansion of their lateral and anterior segments, resulting in an oar-like shape.
Focal rib expansion owing to bone replacement by lipogranulomatous tissue may be seen in Erdheim-Chester disease, or lipid granulomatosis, a disorder of lipid metabolism affecting adult individuals in their fifth through seventh decade of life (Dalinka et al. 1982). Both the visceral organs and the skeletal system are involved by the lipogranulomatous lesions. Long bones in the limbs are always affected (Kushihashi et al. 2000). Radiologic manifestations include bilateral, symmetrical sclerosis of the metaphyseal regions of long bones, patchy sclerosis of the medullary cavity, coarse trabecular pattern, thick cortices, and obliteration of the corticomedullary junction. The epiphyses are spared or only mildly affected. Conspicuous clinical symptoms include xan-thomatous patches in the eyelids, bone pain, cardiac failure, pneumonia, proptosis, exophthalmos, he-patosplenomegaly, weight loss, and pyelonephritis (Resnick et al. 1982). However, clinical symptoms may be entirely absent. Although the precise relationship to the histiocytoses is not known, there is clear evidence that lipid granulomatosis shares clinical, ra-diologic and pathological similarities with Hand-Schuller-Christian disease (Miller et al. 1986). Fucosi-dosis (OMIM 230000) is an autosomal recessive disorder characterized by accumulation of fucosyl compounds (glycolipids, lipoproteins, and a decasac-charide) in the organ tissues. Several types have been recognized, based on the age of appearance and tendency towards progression of the clinical symptoms (type I, early onset, rapid course; type II, onset in the 2nd year of life, moderate progression; type III, late onset, slow progression). Clinical and radiologic manifestations closely resemble those of mucopoly-saccharidoses, including coarse facies, prominent forehead, broad and flat nose, large tongue, thick lips, broad thorax, lumbar hyperlordosis, mental deterioration, thick skin, skull thickening, underdeveloped paranasal sinuses, odontoid hypoplasia, cervical platyspondyly, thoracolumbar gibbus, anterior beaking of the lower thoracic and lumbar vertebrae, short sacrum, absent coccyx, sclerosis and widening of the acetabula, coxa valga, tubulation defect of the long bones, and skeletal maturation delay. Changes in the chest include moderate broadening of the ribs, medial expansion of the clavicles, and underdeveloped glenoid cavities (Brill et al. 1975). Geleophysic dysplasia (OMIM 231050), a very rare autosomal recessive disorder of glycoprotein metabolism resulting in lysosomal accumulation in various tissues, also has features in common with the mucopolysac-charidoses (Spranger et al. 1984). Affected individuals show a 'happy' facies, short stature, short hands and feet due to short, plump tubular bones, joint contractures, hepatosplenomegaly, and progressive valvular cardiac disease. The ribs are broad and the hands short, with broad proximal phalanges and proximally pointing metacarpals; the capital femoral epiphyses are small, and the sella turcica is J-shaped.
Fibrous dysplasia (Jaffe-Lichtenstein disease, OMIM 174800), can affect one bone (monostotic form, 70-80 %), a few bones, or many bones (polyostotic form 20-30%). The polyostotic form of fibrous dysplasia occurs as part of the McCune-Albright syndrome, in combination with precocious puberty and irregular, 'cafe-au-lait' skin pigmentation. Fibrous dysplasia can occur in association with a variety of endocrinopathies, including hyperthyroidism, hy-perparathyroidism, gigantism, diabetes mellitus, and rickets (Garcia et al. 1994). Distinguishing features include expanded fibro-osseous lesions replacing the normal bone tissue, giving rise to areas of bone rarefaction interspersed with areas of reactive sclerosis. Major radiographic manifestations include cyst-like lesions alternating with areas of patchy sclerosis involving the cranial vault, facial bones (often with a unilateral distribution), long bones, pelvis, ribs, and occasionally the spine. Diffuse sclerosis of the skull base is common. Grotesque deformity of the face, fractures, limb shortening, cranial nerve compressions resulting in blindness, deafness, or vestibular dysfunction, and malignant degeneration are among the possible complications (de Smet et al. 1981). Involvement of the ribs by fibrous dysplasia, most commonly associated with the monostotic variety, is common, with a reported prevalence of 30% of affected patients (Malloy et al. 1993). Rib lesions in fibrous dysplasia are almost always asymptomatic. Unilateral, fusiform enlargement of the rib with bone replacement by abnormal tissue and loss of the tra-becular pattern (hazy appearance) is typical. The cortices are thinned and may be either preserved or eroded, with extraosseous extension of the dysplastic tissue (King et al. 1985). The middle ribs are most commonly affected. Myhre syndrome (OMIM 139210) is an association of growth deficiency, maxillary hypoplasia, prognathism, short palpebral fissures, mental retardation, muscular hypertrophy, stiff joints, and cardiac anomalies. Radiologic manifestations include thickening of the skull, prominent mandible, broad ribs and clavicles, platyspondyly, hypoplastic iliac wings, and short tubular bones (Myhre et al. 1981). Rib expansion and sclerosis are sometimes seen in tuberous sclerosis (OMIM 191100), with patchy areas of sclerotic density involving the skull, vertebrae, pelvis, and long bones. Cyst-like defects can be present in the short tubular bones of the hands (Dutton and Singleton 1975; Medley et al. 1976). Rib involvement is relatively uncommon in
Paget disease (Guyer 1981), and takes the form, as in other bones, of osteolytic or osteosclerotic lesions, cortical thickening, bone enlargement, and coarsened trabeculae. The ribs are often modified in patients with severe types of anemia, such as thalassemia major (OMIM 187550) and sickle cell anemia (OMIM 141900), and may show medullary expansion, cortical thinning, osteoporosis, localized radiolucencies, and 'rib-within-a-rib' appearance (Lawson et al. 1981). In sickle cell anemia manifestations include the appearance of diffuse or patchy areas of bone sclerosis related to medullary infarction and fibrosis. Multifocal areas of osteosclerosis can also be seen in renal os-teodystrophy, sometimes alternating with focal lytic masses representing so-called brown tumors (Chew and Huang-Hellinger 1993).
A significant variety of acquired lesions can cause focal or diffuse rib widening and/or thickening, including benign and malignant neoplasms, metastases, aneurysmal cysts, infections, and healing fractures with callus formation.
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