Spondylometepiphyseal dysplasia congenita, Strudwick type

Molecular genetics of the COL2A1-related disorders

Type II collagen, comprised of three identical alpha-1(II) chains, is the major collagen synthesized by chondrocytes, and is found in articular cartilage, vitreous humour, inner ear and nucleus pulposus. Mutations in the collagen type II alpha-1 gene (COL2A1) have been reported to be responsible for a series of abnormalities, known as type II collagenopathies. To date, 16 definite disorders, inherited in an autosomal dominant or recessive pattern, have been described to be associated with the COL2A1 mutations, and at least 405 mutations ranging from point mutations to complex rearrangements have been reported, though the underlying pathogenesis remains unclear. Significant clinical heterogeneity has been reported in COL2A1-associated type II collagenopathies. In this review, we highlight current knowledge of known mutations in the COL2A1 gene for these disorders, as well as genetic animal models related to the COL2A1 gene, which may help us understand the nature of complex phenotypes and underlying pathogenesis of these conditions.

Novel amino acid substitution in the Y-position of collagen type II causes spondyloepimetaphyseal dysplasia congenita

We report on monozygotic twins with short stature and severe spondyloepimetaphyseal dysplasia congenita (SEMDC) from the Polish population. Phenotype of the twin girls resembles spondyloepiphyseal dysplasia congenita Spranger-Wiedemann (SEDC-SW), but shortening of the stature is more severe and the cranioface is normal. The distinctive radiographic features, in spite of similarity to SEDC-SW, indicate different spinal and, notably, severe metaphyseal involvement. Molecular analysis of the COL2A1 gene revealed an A to G transition at nucleotide +79 of exon 41 that converted the codon for arginine at amino acid 792 to a codon for glycine (Arg792Gly). The twins were heterozygous for the mutation and neither parent had this change. The Arg792Gly substitution is located at the Y-position of Gly-X-Y triplet, and it is likely that this substitution decreased the thermal stability of the triple helix and may affect fibril growth by replacement of an arginine residue, which is important for a conformation of the triple helix.

Rhizomelic spondyloepimetaphyseal dysplasia

Spondyloepipmetaphyseal dysplasias (SEMDS) are characterized by flattening of the vertebral bodies and epi-metaphyseal involvement of all the tubular bones. We report a 13 year-old boy with a novel variant of SEMD that presents with rhizomelic/mesomelic shortening of the extremities and normal head, hands and feet. Variable metaphyseal involvement and relatively large proximal humeral and knee epiphyses are further distinctive radiographic features in this patient.

Ultrasonographic evaluation of hip morphology in osteochondrodysplasias

The developing hip in children with osteochondrodysplasias has not been well-described because of delayed ossification and limitations of conventional radiologic techniques. Twenty-four children with various osteochondrodysplasias were evaluated by ultrasonography. Variation in the configuration of the acetabulum included a horizontal acetabular roof owing to delayed iliac development and a notched acetabular roof with lateral bone deficiency. All children had thickened acetabular cartilage except for one child with osteogenesis imperfecta. Coxa vara was a common finding. All neonates displayed a very small beta angle (mean, 42 degrees) because the labrum lay more vertically, secondary to deep engagement of the femoral head in the acetabulum. Proximal femoral ossification was delayed in most children, which allows use of ultrasonography at a later age than is possible in the normal pediatric population. Hip ultrasonography in children with skeletal dysplasias can aid in early diagnosis and is useful in assessing hip morphology and development.

Linkage studies of a Missouri kindred with autosomal dominant spondyloepimetaphyseal dysplasia (SEMD) indicate genetic heterogeneity

A four-generation kindred (14 affected and 10 unaffected members) from Missouri, U.S.A. in which spondyloepimetaphyseal dysplasia (SEMD) had been inherited as an autosomal dominant disorder was investigated for linkage to 13 candidate loci: COL2AI, COL9AI, COL9A2, COL9A3, COL10A1, COL11A1, COL11A2, PSACH, FGFR3, decorin, CRTL1, COMP, and PTHRP. Mutations of COL2A1, COL9A2, COL10, and FGFR3 have been reported previously in the Strudwick type of SEMD, multiple epiphyseal dysplasia type 2 (EDM2), the Schmid type of metaphyseal dysplasia, and in achondroplasia, respectively, and the pseudoachondroplasia (PSACH) locus has been mapped to chromosome 19p12. In addition, mutations in COL9 and COL11A are associated with murine forms of degenerative joint disease and chondroplasia, respectively. The family proved informative for 12 of the 13 loci and was uninformative at the decorin locus. Linkage between this form of SEMD, designated the Missouri variant, SEMDMO, and the 12 informative candidate loci was excluded (LOD scores < -2.00 at theta = 0.005 to 0.15), thereby indicating further genetic heterogeneity in these inherited disorders of bone and cartilage development.

An unknown spondylo-meta-epiphyseal dysplasia in sibs with extreme short stature

In three sibs of Jordanian descent a unique type of severe spondylo-meta-epiphyseal dysplasia results in extreme disproportionate dwarfism. They have a distinct facial appearance with hypotelorism, prognathia, and hypodontia. The limbs are short and the hands and feet stubby. Radiologically, the irregular end plates of the vertebral bodies, the very small and late appearing epiphyseal ossification centres, and the hypoplastic acetabular roofs are most impressive. Histopathologic studies of the growth plate demonstrate characteristic findings with fingerprint-like inclusion bodies in the hypertrophic chondrocytes. This seems to be a distinct, autosomal recessive skeletal dysplasia.

Anthropometry in skeletal dysplasia

Skeletal dysplasia or osteochondrodysplasia is the designation of more than 200 different disorders, that are characterized by abnormalities of the skeleton, disproportional short stature, and a variety of other problems. The underlying biochemical defect is unknown in the vast majority of skeletal dysplasias, and the diagnosis is based on radiological findings and anthropometric measurements. Despite this fact, the information on body proportions in even the more common forms of skeletal dysplasia is scarce. Patients with achondroplasia are often diagnosed shortly after birth. Linear growth is severely compromised with relatively short extremities. Head circumference is above normal and final height ranges from 115 to 145 cm in males and 112 to 137 cm in females. Individuals with hypochondroplasia may go unnoticed until puberty, at which time the growth problem becomes obvious. Sitting height to height ratio is increased, but the body disproportion may not be apparent until puberty. Final height has been reported between 118 and 165 cm. Spondyloepiphyseal and spondylometaepiphyseal dysplasias are characterized by severe impairment of growth both in trunk and extremities, and therefore the sitting height to height ratio may be normal. Final height is severely reduced and ranges from 94 to 132 cm. It is concluded that anthropometric studies of patients with skeletal dysplasia are needed. More quantitative information on body proportions may assist in the diagnostic procedure and ensure that growth promoting therapy, e.g. growth hormone, does not worsen the disproportion.

Micromelic dwarfism--humerus, femur, tibia type. Report of a case

A 12.5-year-old girl with severe micromelic dwarfism and characteristic radiographic findings is reported. The most important phenotypic abnormality was dwarfism (stature < 100 cm); the patient had a normal face and intelligence. The diagnostic radiographic findings were those of spondylo-epimetaphyseal dysplasia characterized by severe shortening of humerus, femur and tibia, hypoplastic but normal-shaped fibula, ulna and radius, uniform shortening of the short tubular bones and moderately severe platyspondyly. These radiographic changes were already present at birth, which should make it possible to recognize the disease in the newborn. We propose naming this disorder micromelic dwarfism-humerus, femur, tibia type.