Severe neurologic manifestations from cervical spine instability in spondylo-megaepiphyseal-metaphyseal dysplasia
Publication Type:Journal Article
Source:American Journal of Medical Genetics, Part C: Seminars in Medical Genetics, Volume 160 C, Number 3, p.230-237 (2012)
Keywords:adolescent, adult, article, bone radiography, cervical spinal cord injury, cervical spine, Cervical Vertebrae, child, clinical article, clinical feature, disease severity, female, gene mutation, Hand, homeodomain protein, homozygosity, human, Humans, infant, laminectomy, male, metacarpal bone, Nervous System, neurologic disease, newborn, nuclear magnetic resonance imaging, ossification, Osteochondrodysplasias, phalanx, physical examination, Preschool, preschool child, priority journal, school child, spine instability, spondylo megaepiphyseal metaphyseal dysplasia, spondyloepiphyseal dysplasia, Tomography, transcription factor Nkx3.2, unclassified drug, X-Ray Computed, Young Adult
Spondylo-megaepiphyseal-metaphyseal dysplasia (SMMD; OMIM 613330) is a dysostosis/dysplasia caused by recessive mutations in the homeobox-containing gene, NKX3-2 (formerly known as BAPX1). Because of the rarity of the condition, its diagnostic features and natural course are not well known. We describe clinical and radiographic findings in six patients (five of which with homozygous mutations in the NKX3-2 gene) and highlight the unusual and severe changes in the cervical spine and the neurologic complications. In individuals with SMMD, the trunk and the neck are short, while the limbs, fingers and toes are disproportionately long. Radiographs show a severe ossification delay of the vertebral bodies with sagittal and coronal clefts, missing ossification of the pubic bones, large round "balloon-like" epiphyses of the long bones, and presence of multiple pseudoepiphyses at all metacarpals and phalanges. Reduced or absent ossification of the cervical vertebrae leads to cervical instability with anterior or posterior kinking of the cervical spine (swan neck-like deformity, kyknodysostosis). As a result of the cervical spine instability or deformation, five of six patients in our series suffered cervical cord injury that manifested clinically as limb spasticity. Although the number of individuals observed is small, the high incidence of cervical spine deformation in SMMD is unique among skeletal dysplasias. Early diagnosis of SMMD by recognition of the radiographic pattern might prevent of the neurologic complications via prophylactic cervical spine stabilization. © 2012 Wiley Periodicals, Inc.
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