Schmid type metaphyseal chondrodysplasia: a spondylometaphyseal dysplasia identical to the "Japanese" type.
BACKGROUND
Schmid-type metaphyseal chondrodysplasia (Schmid MCD) is an autosomal dominant chondrodysplasia resulting from various mutations in the COL10A1 gene. This disorder has been well delineated at a clinical level and has been classified radiographically as a pure metaphyseal chondrodysplasia. A missense mutation in the COL10A1 gene has also been shown to cause a rare spondylo-metaphyseal chondrodysplasia (SMD) named the "Japanese" type which, apart from exhibiting a mild spinal phenotype, shares striking clinical and radiographic similarities to Schmid MCD.


OBJECTIVE
The clinical, radiographic and molecular similarities between Schmid MCD and Japanese SMD led to the hypothesis that these conditions could be identical type X collagenopathies.


METHODS
We analyzed 33 cases of typical Schmid MCD from the International Skeletal Dysplasia Registry, looking specifically for any radiographic evidence of spinal involvement.


RESULTS
We found that in 9.1% (3/33) of cases reviewed there was definite radiographic evidence of spinal involvement comprising mild platyspondyly, vertebral body abnormalities, and end-plate irregularity.


CONCLUSIONS
These data indicate that spinal changes are an uncommon but variable component of Schmid MCD and that this condition and "Japanese" SMD are identical collagen type X disorders. Furthermore, the fact that the specific mutation reported in the family with Japanese type SMD, resulting in the substitution of a glutamic acid residue for a glycine at codon 595 (G595 E), has also been reported in a patient with Schmid MCD strongly supports this conclusion.
Medical Genetics Birth Defects Center, Steven Spielberg Pediatrics Research Center, Cedars-Sinai Medical Center, Los Angeles, California, USA.
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R
Savarirayan
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V
Cormier-Daire
R S
RS
Lachman
D L
DL
Rimoin
D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D010009:Osteochondrodysplasias / Q000000981:diagnostic imaging* / Q000235:genetics; D011859:Radiography; D012042:Registries; D013122:Spinal Diseases / Q000000981:diagnostic imaging* / Q000235:genetics