Abstract
Introduction and Aims: SHOX haploinsufficiency presents with Turner syndrome dysmorphic skeletal features – micrognathia (60%), cubitus valgus (47%), high-arched palate (25%) and Madelung deformity (7%). Idiopathic scoliosis is also present in 11% of Turner syndrome. This clinical observation and radiological study explores the possibility of SHOX haploinsufficiency expression in the scoliotic spine in Turner syndrome.
Method: Turner syndrome presents a mesomelic short stature, thought to result from growth plate dysmorphism, presumably from SHOX gene haploinsufficiency. Forty-five Turner syndrome subjects on the Australian Growth Hormone program were clinically examined for the presence of idiopathic scoliosis. Of another 88 Turner syndrome subjects similarly examined, 46 had received growth hormone and 42 had never received growth hormone. Kosowicz (1959) and Preger (1968) noted irregular vertebral endplates of scoliotic spines in Turner syndrome subjects. This may imply dysmorphic vertebral growth plates. A spinal MRI and plain imaging study of idiopathic scoliosis with/without Turner syndrome was undertaken to examine for vertebral growth plate abnormalities.
Results: This study again demonstrates plain radiographic presence of irregular vertebral endplates of scoliotic spines in Turner syndrome. Spine MR imaging in Turner syndrome failed to clearly demonstrate the growth plates but demonstrated wedge-shaped distal vertebrae in the curve. Similar MR findings were noted in another 20 subjects with various causes of scoliosis. Wedged-shaped intervertebral discs were also noted, but are thought to be secondary changes. Of 87 Turner syndrome subjects from growth hormone programs, 18 (21%) were found to have idiopathic scoliosis. Thirteen of another 46 (28%) subjects who had never received growth hormone were also noted to have idiopathic scoliosis, indicating a combined incidence of 23%. These results contrast with Lippe (1991) and Kim (2001), who noted an incidence of 11% of 163 and 12% of 43 idiopathic scoliosis in Turner syndrome from retrospective observation. However, the incidence of scoliosis (41%) from the radiographic studies of Kosowicz (4/22) and Preger (19/34) is much greater than even the incidence noted clinically from this study.
Conclusion: SHOX haploinsufficiency expression is not yet described in Turner syndrome scoliotic spines, although it has been described in the distal radius (Munns, 2001) in Madelung deformity. The incidence of idiopathic scoliosis in Turner syndrome appears to be much larger than previously recognised, signalling a probable dysmorphic vertebral growth plate cause.
These abstracts were prepared by Editorial Secretary, George Sikorski. Correspondence should be addressed to Australian Orthopaedic Association, Ground Floor, The William Bland Centre, 229 Macquarie Street, Sydney, NSW 2000, Australia.
One or more of the listed authors are receiving or have received benefits or support from a recognised academic body for the pursuance of the study.
