1/2. Short trunk stature, brachydactyly, and platyspondyly in three sibs: a new form of brachyolmia or a new skeletal dysplasia?We present a 27-year-old girl with short trunk stature, generalized rectangular platyspondyly and strike precocious calcification of costal cartilage. She had also brachydactyly, small nails, strabismus and delay of menarche. Her 16-year-old sister had also short trunk stature with severe kyphoscoliosis, hearing loss, brachydactyly, platyspondyly and mild precocious calcification of costal cartilages. Their 12-year-old brother had short trunk stature, kyphoscoliosis, brachydactyly, and platyspondyly but did not show precocious calcification of costal cartilage. The patients shared the following features: short trunk stature, brachydactyly, severe rectangular platyspondyly, broad and short femoral necks and hypoplasia of the ileum. In addition, the older sister had strike precocious calcification of costal cartilage while her sister and brother had severe kyphoscoliosis. Although short trunk stature and severe rectangular platyspondyly without significant epiphyseal or metaphyseal changes were in favor of Hobaek type brachyolmia, this diagnosis was not considered, both because, there were no specific radiological findings of this syndrome, such as elongated vertebral bodies extending beyond the pedicles laterally and all of the patients had brachydactyly which was not present in Hobaek type brachyolmia. The parents were healthy and first cousins signifying autosomal recessive inheritance. We considered that the patients could be affected by a new distinct autosomal recessive type brachyolmia or a new skeletal dysplasia.- - - - - - - - - - ranking = 1keywords = brachydactyly (Clic here for more details about this article) |
2/2. Dominant negative mutations in the C-propeptide of COL2A1 cause platyspondylic lethal skeletal dysplasia, torrance type, and define a novel subfamily within the type 2 collagenopathies.Platyspondylic lethal skeletal dysplasia (PLSD) Torrance type (PLSD-T) is a rare skeletal dysplasia characterized by platyspondyly, brachydactyly, and metaphyseal changes. Generally a perinatally lethal disease, a few long-term survivors have been reported. Recently, mutations in the carboxy-propeptide of type II collagen have been identified in two patients with PLSD-T, indicating that PLSD-T is a type 2 collagen-associated disorder. We studied eight additional cases of PLSD-T and found that all had mutations in the C-propeptide domain of COL2A1. The mutational spectrum includes missense, stop codon and frameshift mutations. All non-sense mutations were located in the last exon, where they would escape non-sense-mediated rna-decay. We conclude that PLSD-T is caused by mutations in the C-propeptide domain of COL2A1, which lead to biosynthesis of an altered collagen chain (as opposed to a null allele). Similar mutations have recently been found to be the cause of spondyloperipheral dysplasia, a non-lethal dominant disorder whose clinical and radiographical features overlap those of the rare long-term survivors with PLSD-T. Thus, spondyloperipheral dysplasia and PLSD-T constitute a novel subfamily within the type II collagenopathies, associated with specific mutations in the C-propeptide domain and characterized by distinctive radiological features including metaphyseal changes and brachydactyly that set them apart from other type 2 collagenopathies associated with mutations in the triple-helical domain of COL2A1. The specific phenotype of C-propeptide mutations could result from a combination of diminished collagen fibril formation, toxic effects through the accumulation of unfolded collagen chains inside the chondrocytes, and alteration of a putative signaling function of the carboxy-propeptide of type 2 collagen.- - - - - - - - - - ranking = 0.22222222222222keywords = brachydactyly (Clic here for more details about this article) |