► [Increased vertical dimensions of the vertebral bodies]
Tall vertebrae are often associated with conditions characterized by severe muscle hypotonia or requiring prolonged recumbency, reflecting diminished compressive forces on the potential longitudinal growth of the vertebral bodies (Donaldson et al. 1985). The resulting increase in the height index (i.e., the ratio of superoinferior diameter to anteroposterior diameter) is approximately proportional to the degree of inactivity (Resnick 1995; Houston and Zales-ki 1967). The increased height of the vertebrae bodies is associated with narrowing of the intervertebral discs (Taylor 1975).
Increased vertebral height may also reflect a primary bone growth defect. Tall vertebrae are found in the lumbar spine in newborns with Down syndrome (OMIM 190685), suggesting a role of genetic factors in the development of this abnormality (Brandner 1972). Other vertebral anomalies reported in this syndrome include atlanto-axial and atlanto-occipital instability associated with asymmetry of the occipital condyles, scoliosis, blocked vertebrae, and flattening of the cervical vertebrae with premature osteo-arthritic changes (Martel and Tishler 1966; Cros et al. 2000; Rosenbaum et al. 1986). In Melnick-Needles syndrome (osteodysplasty OMIM 249420) vertebral changes include increased height with anterior scalloping, enlarged spinal canal with thinned laminae in the lumbar segment, and kyphoscoliosis (Bartolozzi et al. 1983; ter Haar et al. 1982) (Fig. 3.1). Spinal changes in nevoid basal cell carcinoma syndrome (Gorlin syndrome, OMIM 109400) include kyphoscoliosis, spina bifida occulta, cervical spondylolis-thesis, blocked vertebrae, hemivertebrae, and in-
creased superoinferior vertebral diameter resulting in squared vertebral bodies (Barnes et al. 1982; Ki-monis et al. 1997; Lile et al. 1968). An increase in the height ratio is also found in Freeman-Sheldon syndrome (OMIM 193700), in which it is associated with kyphoscoliosis and spina bifida occulta (Fig. 3.2). Proteus syndrome (OMIM 176920), a congenital hamartomatous syndrome characterized by regional gigantism and lymphangiomatous hamartomas, shows overgrowth of a variety of tissues, including the skin,connective and adipose tissue,endothelium, and bones. Overgrowth affects the tubular bones at one extremity, some of the tubular bones in the hands (macrodactyly), the skull, and the vertebral bodies, which appear high and wide, with irregular margins, and dysplastic pedicles and intervertebral discs (Azouz et al. 1987).
Tall vertebrae, together with slender and steeply angled (caudally directed) lower ribs, coxa vara, and gracile hand bones, are features in the rare Fuhrmann dysplasia (dwarfism with tall vertebrae, OMIM 126950),which may be of autosomal dominant inheritance (Fuhrmann et al. 1972). The increased height of the vertebral bodies in this disorder is thought to be secondary to severe muscular hypotonia. (This disorder must not be confused with Fuhrmann syndrome (OMIM 228930), an autosomal recessive disorder featuring cleft lip/palate, agenesis of fibula and ulna, bowing of femur, and joint contractures.) Tall vertebrae are also features in acro-cranio-facial dysostosis (OMIM 201050), a condition with prominent changes in the skull (craniosynostosis), facial bones (hypertelorism, proptosis, cleft palate, microgna-thia), and hands and feet (short 1st metacarpal and metatarsal) (Kaplan et al. 1988).
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