Spondyloepimetaphyseal dysplasia with multiple dislocations, leptodactylic type: report of a new patient and review of the literature

Involvement of kinesins in skeletal dysplasia: a review

Skeletal dysplasias are group of rare genetic diseases resulting from mutations in genes encoding structural proteins of the cartilage extracellular matrix (ECM), signaling molecules, transcription factors, epigenetic modifiers, and several intracellular proteins. Cell division, organelle maintenance, and intracellular transport are all orchestrated by the cytoskeleton-associated proteins, and intracellular processes affected through microtubule-associated movement are important for the function of skeletal cells. Among microtubule-associated motor proteins, kinesins in particular have been shown to play a key role in cell cycle dynamics, including chromosome segregation, mitotic spindle formation, and ciliogenesis, in addition to cargo trafficking, receptor recycling, and endocytosis. Recent studies highlight the fundamental role of kinesins in embryonic development and morphogenesis and have shown that mutations in kinesin genes lead to several skeletal dysplasias. However, many questions concerning the specific functions of kinesins and their adaptor molecules as well as specific molecular mechanisms in which the kinesin proteins are involved during skeletal development remain unanswered. Here we present a review of the skeletal dysplasias resulting from defects in kinesins and discuss the involvement of kinesin proteins in the molecular mechanisms that are active during skeletal development.

Whole-exome sequencing identifies mutations of KIF22 in spondyloepimetaphyseal dysplasia with joint laxity, leptodactylic type

Spondyloepimetaphyseal dysplasia with joint laxity (SEMDJL), leptodactylic (lepto-SEMDJL) or Hall type, is an autosomal-dominant skeletal dysplasia manifesting with short stature, joint laxity with dislocation(s), limb malalignment, and spinal deformity. Its causative gene mutation has not yet been discovered. We captured and sequenced the exomes of eight affected individuals in six unrelated kindreds (three individuals in a family and five simplex individuals). Five novel sequence variants in KIF22, which encodes a member of the kinesin-like protein family, were identified in seven individuals. Sanger sequencing of KIF22 confirmed that c.443C>T (p.Pro148Ser) cosegregated with the phenotype in the affected individuals in the family; c.442C>T (p.Pro148Leu) or c.446G>A (p.Arg149Gln) was present in four of five simplex individuals, but was absent in unaffected individuals in their family and 505 normal cohorts. KIF22 mRNA was detected in human bone, cartilage, joint capsule, ligament, skin, and primary cultured chondrocytes. In silico analysis of KIF22 protein structure indicates that Pro148 and Arg149 are important in maintaining hydrogen bonds in the ATP binding and motor domains of KIF22. We conclude that these mutations in KIF22 cause lepto-SEMDJL.

Recurrent dominant mutations affecting two adjacent residues in the motor domain of the monomeric kinesin KIF22 result in skeletal dysplasia and joint laxity

Spondyloepimetaphyseal dysplasia with joint laxity, leptodactylic type (lepto-SEMDJL, aka SEMDJL, Hall type), is an autosomal dominant skeletal disorder that, in spite of being relatively common among skeletal dysplasias, has eluded molecular elucidation so far. We used whole-exome sequencing of five unrelated individuals with lepto-SEMDJL to identify mutations in KIF22 as the cause of this skeletal condition. Missense mutations affecting one of two adjacent amino acids in the motor domain of KIF22 were present in 20 familial cases from eight families and in 12 other sporadic cases. The skeletal and connective tissue phenotype produced by these specific mutations point to functions of KIF22 beyond those previously ascribed functions involving chromosome segregation. Although we have found Kif22 to be strongly upregulated at the growth plate, the precise pathogenetic mechanisms remain to be elucidated.

A distinct form of spondyloepimetaphyseal dysplasia with joint laxity (SEMDJL)-leptodactylic type: radiological characteristics in seven new patients

OBJECTIVE

This study presents seven cases of a rare but distinctive form of spondyloepimetaphyseal dysplasia with joint laxity-leptodactylic or Hall type to emphasize the characteristic clinical and radiological findings.

MATERIALS AND METHODS

A multiinstitutional retrospective review was performed on seven patients. The patient population consisted of one family with an affected mother and two siblings and four unrelated patients; there were one adult, aged 40 years, and six children, ranging in age from 3 to 12 years. The gender ratio of females to males was 5 to 2. We reviewed the clinical data and skeletal surveys and focused on radiographs of the pelvis, knees, hands, and spine.

RESULTS

The outstanding clinical features were short stature, midface hypoplasia, and multiple dislocations and/or ligamentous laxity of the large joints, particularly at the knees with a genu valgum or varum deformity. Of seven patients, six patients showed normal intellect but one patient had mild mental retardation. The main radiological features included small, irregular epiphyses, metaphyseal irregularity with vertical striations that was a constant finding at the knees, constricted femoral necks, delayed ossification of the carpal bones, and slender metacarpals. Progressive thoracolumbar scoliosis was evident with aging; however, the vertebral bodies appeared normal in height or mild platyspondyly was noted.

CONCLUSION

In view of the orthopedic management of multiple joint dislocations and ligamentous laxity of the large joints, awareness of this disease entity and diagnostic precision solely based on radiological findings is of importance, particularly as the disorder is currently more common than initially reported.

Spondyloepimetaphyseal dysplasia with joint laxity, leptodactylic or Hall type: report of a case with normal face and literature review

We have documented the clinical and radiological features of a girl with a severe form of spondyloepimetaphyseal dysplasia with joint laxity, leptodactylic or Hall type, which is associated with marked articular hypermobility. This condition is to be differentiated clinically from generalized hypermobility syndromes specifically Ehlers-Danlos syndrome and Larsen syndrome. The radiographic differential diagnosis is with the group of spondyloepimetaphyseal dysplasias specifically spondyloepimetaphyseal dysplasia with joint laxity and sponastrime dysplasia.

Osseous dysplasia with severe short stature, multiple dislocations, and delayed bone age: Report on a second Lebanese patient

We describe a young girl with severe pre- and postnatal short stature, bilateral dislocation of hips, knees and elbows, and right clubfoot. Skeletal investigations disclosed an anisospondyly, the absence of ossification of the odontoid apophysis and of fusion of the neural arches of the cervical vertebrae, abnormal L3 and L4 vertebrae, partial agenesis of the coccyx, abnormal and sub-luxated radial heads, bilateral dislocation of the hips, dysplastic acetabulae, pseudoacetabulae, hypoplasia of the femoral heads, short femoral necks, short long bones with thin diaphyses, widening of the medullary canal and thinning of the cortical one, slightly enlarged metaphyses, and diffuse osseous demineralization. Bone age was delayed. The girl's parents are first cousins. Differential diagnoses are discussed and the possibility is raised that this might be a second patient with clinical features indicating an entity recently described in a young Lebanese boy [Mégarbané and Ghanem (2004); Am J Med Genet Part A 130A: 107-109]. A clinical follow-up of the latter patient is also reported.