International nosology and classification of constitutional disorders of bone (2001)

Infantile osteopetrosis in four Thai infants

Four Thai infants, aged between 4 and 23 months, had progressive abdominal distension, pallor and delayed or regressed developmental milestones, with age at onset of 1 month, 3 months, 4 months and 1 month, respectively. Clinical findings consisted of growth and developmental retardation, anemia, frontal bossing, marked hepatosplenomegaly, and hearing and visual impairment. Laboratory findings revealed moderate anemia, leukocytosis and thrombocytopenia. The radiographic findings comprised generalized sclerosis of all bones, including the cranial base, and obliteration of the medullary canals and trabecular patterns. The first and second patients, who had swelling of the wrist joints and prominent costochondral junctions, had hypophosphatemia, elevated levels of serum alkaline phosphatase, and metaphyseal flaring on their radiographs, which was consistent with infantile osteopetrosis complicated by rickets. After Stoss therapy, there were biochemical and radiological responses suggesting vitamin D deficiency in the first patient, but not in the second. The third patient, who had hypocalcemia, hypophosphatemia and normal levels of serum alkaline phosphatase, received vitamin D at 3000 units per day, without improvement. Despite frequent blood transfusions, all patients continued to deteriorate and were finally lost to follow-up. Rickets should be identified and treated at the onset, because treatment of rickets leads to improvement in well-being and an adequate clinical response to bone marrow transplantation.

Perinatally lethal, short-limbed dwarfism with distinct features -- Schneckenbecken dysplasia

The clinical, radiographical and histological features are described for a case of Schneckenbecken dysplasia, presenting antenatally with increased nuchal thickness and severe skeletal dysplasia. Intrauterine death occurred in the third trimester and the precise diagnosis was made postmortem. This is the first case reported in the UK.

Growing bone knowledge

Molecular dissection of genetic bone diseases continues to deliver exciting insights on developmental control of skeletal patterning and growth. But will diagnostic tests become available to the genetic community on a wide basis?

A transcriptional profile of human fetal cartilage

Cartilage plays a central role in the patterning and growth of the skeletal elements, and mutations in genes expressed in cartilage are responsible for at least 250 distinct clinical conditions, the osteochondrodysplasias. While recent progress has been made in characterizing the genes that define cartilage biology, there are only limited data describing the gene expression profile of human cartilage. Here we describe the sequences and identities of 6266 clones from an 18-20-week human fetal cartilage cDNA library. Among the sequences, BLAST analysis identified 2404 individual transcripts. Of these, 1775 were defined as derived from characterized genes and the remaining 629 were classified as representing the products of uncharacterized genes. Analysis of the relative representation of each individual transcript showed that the 186 most abundant cDNAs in the library accounted for almost half (47.7%) of the clones. The most highly expressed gene was COL2A1, accounting for 4.15% of all cDNA clones. The cDNAs identified included clones derived from 27 genes which, when mutated, result in disorders of skeletal patterning, development and growth. There were cDNAs representing 22 genes encoding collagen subunits. The genes encoding the identified cDNAs represent candidates for the approximately 100 osteochondrodysplasias for which the causative gene has not yet been identified. Moreover, these data provide an extensive profile of human fetal cartilage gene expression at this developmental stage.

Lack of correlation between the type ofCOL1A1orCOL1A2mutation and hearing loss in osteogenesis imperfecta patients

Osteogenesis imperfecta (OI) is caused by mutations in COL1A1 and COL1A2 that code for the alpha1 and alpha2 chains of type I collagen. Phenotypes correlate with the mutation types in that COL1A1 null mutations lead to OI type I, and structural mutations in alpha1(I) or alpha2(I) lead to more severe OI types (II-IV). However, correlative analysis between mutation types and OI associated hearing loss has not been previously performed. A total of 54 Finnish OI patients with previously diagnosed hearing loss or age 35 or more years were analyzed here for mutations in COL1A1 or COL1A2. Altogether 49 mutations were identified, of which 41 were novel. The 49 mutations represented the molecular genetic background of 41.1% of the Finnish OI population. A total of 38 mutations were in COL1A1 and 11 were in COL1A2. Of these, 16 were glycine substitutions and 16 were splicing mutations in alpha1(I) or alpha2(I). In addition, 17 null allele mutations were detected in COL1A1. A total of 32 patients (65.3%) with a mutation had hearing loss. That is slightly more than in our previous population study on Finnish adults with OI (57.9%). The association between the mutation types and OI type was statistically evident. Patients with COL1A1 mutations more frequently had blue scleras than those with COL1A2 mutations. In addition, patients with COL1A2 mutations tended to be shorter than those with COL1A1 mutations. However, no correlation was found between the mutated gene or mutation type and hearing pattern. These results suggest that the basis of hearing loss in OI is complex, and it is a result of multifactorial, still unknown genetic effects.

Management of disabilities associated with achondroplasia

Achondroplasia is a skeletal dysplasia that manifests as short stature. Impairment and complications range over many disciplines including orthopedics, pediatrics, neurology, and otolaryngology. The major impairments of the extremities are short limbs, limited elbow and hip extension, and knee and leg deformities that can cause disabilities in arm function and locomotion. Hydrocephalus, a narrow foramen magnum, spinal deformity, and spinal canal stenosis can cause neurological problems, leading to disabilities in locomotion, communication, and learning. Malfunctions of the otolaryngeal system such as otitis media, upper respiratory obstruction, deafness, speech delay, and malocclusion are interrelated and can also lead to disabilities in communication and learning. Although such disabilities may cause social handicaps, most children receive a normal education. Their social maturity scale is comparable to that of normal children, but their scale of locomotion is not. The reported occupational level of female adult patients is lower than that of their unaffected siblings. When managing patients, orthopedists should consider the overall aspects of achondroplasia, including natural development and complications other than orthopedic factors.

Stapes surgery in osteogenesis imperfecta in Finland

We present the surgical findings and audiometric results of ear surgery performed between 1961 and 2002 on 33 Finnish patients (43 operations) with osteogenesis imperfecta (OI). The mean age at the time of the first operation was 30.1 years. The typical surgical findings were a thick, fixed, or obliterated footplate, thick and vascular mucosa with an excessive tendency to bleed, and elastic, fractured, or atrophic stapes crura. As compared with previous studies, the hearing gain was poorer and the remaining postoperative gap was greater for the 43 operations analyzed. The results of this nationwide study, however, may not be directly comparable with operative results of non-population studies. On the other hand, the hearing gain in our study was better in university hospitals than in central hospitals and, furthermore, was comparable with that of previous studies after surgery performed by a single surgeon in a university hospital. Conductive hearing loss related to OI may be successfully treated with surgery in most patients. The rarity of the disease, leading to small annual numbers of operations, the variable surgical findings, and the profuse bleeding tendency of the middle ear, as well as the audiometric results in this study, support centralization of ear surgery in OI patients.

Spondyloepiphyseal dysplasia omani type: A new recessive type of SED with progressive spinal involvement

We report a large inbred kindred from Oman with a distinct type of spondyloepiphyseal dysplasia (SED). We evaluated eight individuals from two consanguineous sibships, one male and seven females between the ages of 2 and 22. The pedigrees strongly suggest autosomal recessive inheritance and both families are likely to be related through distant consanguineous loops. The clinical features include near to normal length at birth, short stature with final height of 110-130 cm, shortening of the upper segment due to severe progressive kyphoscoliosis, severe arthritic changes with joint dislocations, rhizomelic limbs, genu valgum, cubitus valgus, mild brachydactyly, camptodactyly, microdontia, and normal intelligence. Minor radiographic metaphyseal changes were found, but major manifestations were in the spine and the epiphyses. During the first year of life the vertebral bodies are of normal height but the endplates are irregular and intervertebral space is narrow. With age, the vertebral endplates become increasingly irregular, the intervertebral space diminishes further and individual vertebrae start to fuse resulting in a severe short trunk dwarfism with kyphoscoliosis. The epiphysis are small and precocious osteoarthropathy was observed involving small and large joints. The elbow, wrist, and hip joints were affected starting in infancy and showed restricted movement. Osteoarthropathy and spinal involvement resulted in physical handicap in early adulthood. Comparison of these patients with other skeletal dysplasias suggests that they represent a previously undescribed variant of SED.

Depletion of cartilage collagen fibrils in mice carrying a dominant negative Col2a1 transgene affects chondrocyte differentiation

We have generated transgenic mice harboring the deletion of exon 48 in the mouse alpha1(II) procollagen gene (Col2a1). This was the first dominant negative mutation identified in the human alpha1(II) procollagen gene (COL2A1). Patients carrying a single allele with this mutation suffer from a severe skeletal disorder called spondyloepiphyseal dysplasia congenita (SED). Transgenic mice phenotype was neonatally lethal with severe respiratory failure, short bones, and cleft palate. Transgene mRNA was expressed at high levels. Growth plate cartilage of transgenic mice presented morphological abnormalities and reduced number of collagen type II fibrils. Chondrocytes carrying the mutation showed altered expression of several differentiation markers, like fibroblast growth factor receptor 3 (Fgfr3), Indian hedgehog (Ihh), runx2, cyclin-dependent kinase inhibitor P21CIP/WAF (Cdkn1a), and collagen type X (Col10a1), suggesting that a defective extracellular matrix (ECM) depleted of collagen fibrils affects chondrocytes differentiation and that this defect participates in the reduced endochondral bone growth observed in chondrodysplasias caused by mutations in COL2A1.

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

A 6-year-old boy with congenital hip dislocation, developmental delay, short stature, macrocephaly, low set ears, short neck, and hyperlaxity of the wrists and fingers is described. Radiographs disclosed mainly the presence of thoracic scoliosis, narrow interpedicular distances, metaphyseal vertical striations, very small irregular epiphyses, right hip dislocation, luxation of both elbows, and severe delay of ossification of the epiphyses and the carpal bones. These features are very close to the newly described entity: spondyloepimetaphyseal dysplasia and multiple dislocations. This patient brings to light the differential diagnosis and confirms the specificity of the radiological findings of this new entity.

Genetic Analysis of Short Stature

Short stature is a major concern for patients and their parents, and represents a diagnostic challenge to the clinician. A correct diagnosis is of particular importance in view of the availability of effective, but costly, therapy in a small subset of cases. Many different genetic etiologies of short stature are known. Therefore, chromosome as well as molecular analysis are requisite diagnostic investigations in children with short stature. Particularly in the group of children with idiopathic short stature, possibilities of molecular analysis are often underestimated. Important options are UPD7 and the FGFR3, SHOX, GH1 and GHR genes. Furthermore, analysis of the IGF and IGF1R genes should be considered. We propose a flow chart for molecular analysis in short stature.

Spondyloepiphyseal dysplasia tarda (SEDL, MIM #313400)

Spondyloepiphyseal dysplasia tarda (SEDL) is a radiologically distinct, X-chromosome linked primary skeletal dysplasia characterised by disproportionate short-trunked short stature, dysplasia of the large joints (hip) and flattened thoracic and lumber vertebral bodies. Molecular basis for SEDL has been elucidated by the identification of various mutations (currently >30) in the SEDL gene from Xp22 region. The function of the SEDL protein is not known although it is speculated that it may participate in the ER-to-Golgi transport as part of a novel highly conserved multiprotein TRAPP complex.

Genetic disorders of the skeleton: a developmental approach

Although disorders of the skeleton are individually rare, they are of clinical relevance because of their overall frequency. Many attempts have been made in the past to identify disease groups in order to facilitate diagnosis and to draw conclusions about possible underlying pathomechanisms. Traditionally, skeletal disorders have been subdivided into dysostoses, defined as malformations of individual bones or groups of bones, and osteochondrodysplasias, defined as developmental disorders of chondro-osseous tissue. In light of the recent advances in molecular genetics, however, many phenotypically similar skeletal diseases comprising the classical categories turned out not to be based on defects in common genes or physiological pathways. In this article, we present a classification based on a combination of molecular pathology and embryology, taking into account the importance of development for the understanding of bone diseases.

Talo-patello-scaphoid osteolysis, synovitis, and short fourth metacarpals in sisters: a new syndrome?

Osteolysis syndromes are characterized by resorption of affected bones with associated swelling and pain. Various forms of multicentric osteolysis syndromes including autosomal dominant and recessive carpal-tarsal osteolysis, Torg, François, Whyte-Hemingway, Hajdu-Cheney, Winchester, and other forms have been described. Most present in pre-school years with extensive involvement and destruction of multiple bones. We present a sister-pair, both of whom presented in early teenage, i.e., 13 and 15.5 years, respectively, with bilateral ankle, knee, and later, wrist pain. Radiological examination revealed bilateral osteolysis of tali, scaphoids, and patellae, and short fourth metacarpals in both sisters. Further investigation revealed absence of renal involvement, a normal excretion of amino acids, mucopolysaccharides and oligosaccharides, and presence of chronic synovitis in both sisters. Both parents and a younger brother were without radiographic or clinical evidence of the disease and there was no history of consanguinity. Thus, our sister-pair presented with the same carpal and tarsal bone involvement at a much later age, with evidence of chronic synovitis, along with short fourth metacarpals (brachydactyly type E changes) and without renal disease, suggesting a new syndrome with probable autosomal recessive inheritance.

Vestibular dysfunction in adult patients with osteogenesis imperfecta

Progressive hearing loss is a major symptom in osteogenesis imperfecta (OI), a genetic brittle bone disease. Vertigo is frequently associated with otosclerosis in which the hearing loss clinically resembles that in OI. Vertigo is also common in basilar impression (BI) found in up to 25% of adult OI patients. In order to evaluate the cause, frequency, and characteristics of vertigo in OI, 42 patients were studied by interview, clinical examination, and audiological examination supplemented with electronystagmography (ENG) and lateral skull radiography. Audiometry showed hearing loss in 25 patients (59.5%). Nine patients (21%) displayed abnormal skull base anatomy in the forms of basilar impression, basilar invagination, or both, all designated here as BI. Twenty-two patients (52.4%) reported vertigo, mostly of floating or rotational sensation of short duration. Patients with hearing loss tended to have more vertigo than patients with normal hearing. Vertigo was not correlated with type of hearing loss or auditory brain-stem response (ABR) pathology. ENG was abnormal in 14 patients (33.3%). No dependency was found between vertigo and deviant ENG results. Patients with BI tended to have more vertigo than patients with normal skull base but the difference was not statistically significant. Neither ENG pathology, nor the presence or type of hearing loss showed correlation with BI. In conclusion, vertigo is common in patients with OI. In most cases, it may be secondary to inner ear pathology, and in only some patients does BI explain it. Since some OI patients without BI or hearing loss also suffer from vertigo, further clinical and neurological studies are needed to define the pathogenesis of vertigo in OI.

Paternal uniparental disomy 14: introducing the "coat-hanger" sign

Paternal uniparental disomy for chromosome 14 (patUPD14) is a rare condition, this being the eighth report. A male infant, born prematurely, was noted to have extremely lax skin and bilateral inguinal hernias. Skin biopsy confirmed the clinical diagnosis of congenital cutis laxa, but this did not explain the limb abnormalities. Radiographic findings (particularly the "coat-hanger" configuration of the ribs on the chest radiograph), suggested a diagnosis of patUPD14, which was confirmed following DNA analysis. The patient died after prolonged respiratory failure. This combination of patUPD14 and congenital cutis laxa has not previously been described. Radiology can play a pivotal role in guiding the geneticist's choice of investigation.

The genetic basis for skeletal diseases

We walk, run, work and play, paying little attention to our bones, their joints and their muscle connections, because the system works. Evolution has refined robust genetic mechanisms for skeletal development and growth that are able to direct the formation of a complex, yet wonderfully adaptable organ system. How is it done? Recent studies of rare genetic diseases have identified many of the critical transcription factors and signalling pathways specifying the normal development of bones, confirming the wisdom of William Harvey when he said: "nature is nowhere accustomed more openly to display her secret mysteries than in cases where she shows traces of her workings apart from the beaten path".

Analysis of clones from a human cartilage cDNA library provides insight into chondrocyte gene expression and identifies novel candidate genes for the osteochondrodysplasias

To begin to define the gene expression pattern in fetal cartilage and to identify uncharacterized candidate genes for the osteochondrodysplasias, we analyzed clones from a fetal cartilage cDNA library. Sequence analysis of 420 cDNA clones identified 210 clones derived from established genes but, for many of them, expression in cartilage had not been previously reported. Among the established genes were 14 genes known to produce skeletal abnormalities in either humans or mice when mutated. Thirty-two uncharacterized genes and their respective chromosomal positions were also identified. To further understand the expression profile of these genes in fetal cartilage, we constructed a cDNA microarray utilizing the clones. The microarray was used to determine which genes had higher expression in cartilage as compared with dedifferentiated, cultured chondrocytes. Many of the established genes, as well as five of the uncharacterized genes, had increased expression in cartilage, suggesting an important role for these genes in the differentiated state of chondrocytes. These data provide new candidate genes for the osteochondrodysplasias and demonstrate the usefulness of cartilage cDNA microarrays in expanding our understanding of the complexity of fetal cartilage gene expression.

Radiological diagnosis of the constitutional disorders of bone. As easy as A, B, C?

Although many constitutional disorders of bone are individually rare, collectively they make up a large group of disorders. They are broadly classified into osteochondrodysplasias and dysostoses. Because of the rarity of some of these conditions, they can be difficult to diagnose. Members of the International Dysplasia Group meet regularly to update and clarify the nomenclature. The last meeting was in Oxford in 2001. This article attempts to highlight the differences between the osteochondrodysplasias and the dysostoses, and provides a systematic approach to their radiological diagnosis.

Mental retardation and abnormal skeletal development (Dyggve-Melchior-Clausen dysplasia) due to mutations in a novel, evolutionarily conserved gene

Dyggve-Melchior-Clausen dysplasia (DMC) and Smith-McCort dysplasia (SMC) are similar, rare autosomal recessive osteochondrodysplasias. The radiographic features and cartilage histology in DMC and SMC are identical. However, patients with DMC exhibit significant developmental delay and mental retardation, the major features that distinguish the two conditions. Linkage studies localized the SMC and DMC disease genes to chromosome 18q12-21.1, providing evidence suggesting that they are allelic disorders. Sequence analysis of the coding exons of the FLJ90130 gene, a highly evolutionarily conserved gene within the recombination interval defined in the linkage study, identified mutations in SMC and DMC patients. The affected individuals in two consanguinous DMC families were homozygous for a stop codon mutation and a frameshift mutation, respectively, demonstrating that DMC represents the FLJ90130-null phenotype. The data confirm the hypothesis that SMC and DMC are allelic disorders and identify a gene necessary for normal skeletal development and brain function.

Longterm follow-up in chondrodysplasia punctata, tibia-metacarpal type, demonstrating natural history

We report the longterm clinical and radiological progression in three unrelated patients with the tibia-metacarpal form of chondrodysplasia punctata (CDP-TM). The patients were followed for 37, 25, and 32 years, respectively. At follow-up intellectual function was normal, and physical function was well preserved. There was also marked resolution of several significant early radiographic features. The patients attained adult heights of 152, 138, and 148 cm. Two patients had chronic serous otitis media requiring tympanostomy tubes during childhood. One patient suffered persisting back pain related to spinal stenosis and required lumbar laminectomy at the age of 26 years. One patient had hip dysplasia requiring orthopedic surgical intervention. All patients had recurrent patella dislocation. Sterol and very long chain fatty acid profiles, FISH analysis for SHOX gene deletions, blood lymphocyte karyotype, and phytanic acid levels were normal in those tested, and no mutations in arylsulfatase D and E genes were detected. These data suggest that the longterm clinical and functional prognosis in this condition appears to be better than that expected based on initial clinical and radiological findings.