Severe neurologic manifestations from cervical spine instability in spondylo-megaepiphyseal-metaphyseal dysplasia.
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.
Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands.
Marleen
M
Simon
Ana Belinda
AB
Campos-Xavier
Lauréane
L
Mittaz-Crettol
Eugenia Ribeiro
ER
Valadares
Daniel
D
Carvalho
Carlos Eduardo
CE
Speck-Martins
Sheela
S
Nampoothiri
Yasemin
Y
Alanay
Ercan
E
Mihci
Yolande
Y
van Bever
Nuria
N
Garcia-Segarra
Denise
D
Cavalcanti
Geert
G
Mortier
Luisa
L
Bonafé
Andrea
A
Superti-Furga
D000293:Adolescent; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006225:Hand / Q000000981:diagnostic imaging; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009420:Nervous System / Q000473:pathology*; D010009:Osteochondrodysplasias / Q000000981:diagnostic imaging / Q000473:pathology*; D014057:Tomography, X-Ray Computed; D055815:Young Adult