Mesomelic dysplasias associated with the HOXD locus are caused by regulatory reallocations

Human families with chromosomal rearrangements at 2q31, where the human HOXD locus maps, display mesomelic dysplasia, a severe shortening and bending of the limb. In mice, the dominant Ulnaless inversion of the HoxD cluster produces a similar phenotype suggesting the same origin for these malformations in humans and mice. Here we engineer 1 Mb inversion including the HoxD gene cluster, which positioned Hoxd13 close to proximal limb enhancers. Using this model, we show that these enhancers contact and activate Hoxd13 in proximal cells, inducing the formation of mesomelic dysplasia. We show that a secondary Hoxd13 null mutation in-cis with the inversion completely rescues the alterations, demonstrating that ectopic HOXD13 is directly responsible for this bone anomaly. Single-cell expression analysis and evaluation of HOXD13 binding sites suggests that the phenotype arises primarily by acting through genes normally controlled by HOXD13 in distal limb cells. Altogether, these results provide a conceptual and mechanistic framework to understand and unify the molecular origins of human mesomelic dysplasia associated with 2q31.

miR-21 is involved in skeletal deficiencies of zebrafish embryos exposed to polychlorinated biphenyls

Polychlorinated biphenyl (PCB) exposure increases the incidence and severity of skeletal diseases, but little is known about the mechanisms that mediate this relationship. We exposed zebrafish embryos to PCB₁₂₅₄ and assessed the changes in bone morphology protein receptor II (BMPRII), which is involved in bone formation and embryonic development, miRNA-21, for which BMPRII is a known target, and calcium metabolism. PCB₁₂₅₄ upregulated the expression of miR-21 and suppressed BMPRII expression. The inhibition of miR-21 reversed the downregulation of BMPRII and alleviated the PCB₁₂₅₄-induced loss of calcium. These findings suggest new biomarkers of developmental defects of the skeleton caused by PCBs.

Approach to the diagnosis of skeletal dysplasias: Experience at a center with limited resources

PURPOSE

A fetus with skeletal disorder poses diagnostic challenges in a resource-poor setting with limited management options. The objective of the study was to develop a step-by-step approach for the diagnosis of skeletal dysplasia in light of the limited resources available.

METHODS

An algorithmic approach was used. The assessment for lethality was the first step, followed by the evaluation for fractures. In cases without evidence of fracture, severe constriction of thorax or associated polydactyly were searched for. In cases without severe thoracic constriction, the severity of micromelia was evaluated. After delivery, fetal examination was done to ascertain the etiology.

RESULTS

During the 6-year period, 41 cases with shortened long bones were fully evaluated. Lethality was suspected in 30 cases. Fracture and beading were present in eight cases, and severe thoracic constriction with polydactyly was observed in seven cases. Mild micromelia was seen in 19 cases and severe micromelia in 7 cases. Among lethal skeletal dysplasias, thanatophoric dysplasia was most common (six cases). Among nonlethal skeletal dysplasias, achondroplasia was seen in eight cases.

CONCLUSIONS

Lethality of skeletal dysplasia could be predicted on prenatal ultrasound with 100% accuracy. The step-by-step approach was helpful to characterize skeletal dysplasias. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 44:529-539, 2016.

Prenatal diagnosis of proximal focal femoral deficiency: Literature review of prenatal sonographic findings

Proximal focal femoral deficiency (PFFD) is a rare musculoskeletal malformation that occurs in 0.11-0.2 per 10,000 live births. This congenital anomaly involves the pelvis and proximal femur with widely variable manifestations, from mild femoral shortening and hypoplasia to the absence of any functional femur and acetabular aplasia. Prenatal diagnosis of PFFD is still a challenge, but early recognition of this malformation could provide useful information to both parents and physicians concerning management and therapeutic planning. For this review, we analyzed all the cases of prenatally diagnosed PFFD that were reported in the literature from 1990 to 2014 and provide a description of the most common prenatal sonographic findings.

Imaging in the diagnosis of rare diseases

A disease is considered rare if it affects no more than 5 in 10,000 people. More than six thousand rare diseases have been detected so far and they affect 6-8% of the population which equals 2.3-3 million people in Poland. Some of the rare diseases are already diagnosed in utero, e.g. skeletal dysplasias on ultrasonography or central nervous system diseases on magnetic resonance imaging (MRI). Many cases are finally diagnosed after radiologist's suggestion in a radiological report. Although diagnostic imaging cannot be considered as a basis for diagnosis of most of rare diseases, these studies represent an important element in the diagnostic chain. The complicated and long process of diagnosis may be significantly shortened by suggestions of the radiologist, based on the observation of these elements of radiological appearance of the lesions that are characteristic for a particular group of diseases, or even for a particular disease entity. However, the absolute condition for success is the close clinical-radiological cooperation, with clinicians providing the radiologists with their knowledge of patient's history, clinical manifestations, and the results of other investigations.

Use of low dose computed tomography with 3D reconstructions for the prenatal evaluation of suspected skeletal dysplasia

BACKGROUND

Sonographic evaluation of congenital skeletal dysplasias is often challenging. Ultrasound may be limited in demonstrating the skeleton and may overlook specific signs of skeletal abnormality. Computed tomography (CT) with 3D reconstruction was proposed as an aid in the diagnosis of skeletal dysplasias.

OBJECTIVES

To describe our experience with 3D-CT imaging for the evaluation of suspected skeletal dysplasias.

METHODS

The study group comprised 20 pregnant women carrying 22 fetuses, referred for further evaluation by CT following sonographic suspicion of fetal skeletal dysplasia at 17-39 weeks of gestation. Examinations were performed using various CT protocols. Radiation exposure was decreased during the study period, with eventual lowering of the dose to 1-3 mSv. Meticulous review of the skeleton and long bone measurements were performed on 3D reconstructions. For cases of pregnancy termination, the postmortem diagnosis was compared retrospectively with the CT findings.

RESULTS

Very low dose CT protocols provided excellent diagnostic images. Of 22 fetuses suspected of having skeletal dysplasia on ultrasound, 8 were found by CT to be dysplastic and in 7 the pregnancy was terminated. Postmortem findings, when available, concurred with the CT diagnosis. The remaining 14 fetuses within this cohort were found to be normal according to CT and were carried to term.

CONCLUSIONS

3D-CT may be a valuable complimentary imaging tool to ultrasound for the diagnosis of skeletal dysplasias. With low dose protocols, this examination is relatively safe, and in the appropriate clinical context may assist in making difficult decisions prenatally.

[Fetal therapy of skeletal dysplasias]

Three types of fetal therapy of skeletal dysplasias, as enzyme replacement, in utero stem cell transplantation, and gene therapy, are reviewed. Clinical trial of recombinant ALP for infantile hypophosphatasia has already started in Japan. In future, such enzyme replacement therapy is expected to be adapted to fetus. There are several reports of mesenchymal stem cell transplantation for osteogenesis imperfecta fetus. These case reports have showed that stem cell transplantation is safe and to some extent works in patients. No clinical trial for gene therapy has been reported. Recently, the study of gene therapy of using HPP fetal mouse showed an excellent therapeutic effect. Fetal therapy of skeletal dysplasias is still the stage of research because of the safety and the ethical issues. However, in order to treat severe cases of skeletal dysplasias which abnormal development has been already completed at birth, fetal therapy at an early stage would be demanded.

Prenatal diagnosis of unilateral proximal femoral focal deficiency at 19 weeks' gestation: case report and review of the literature

Proximal femoral focal deficiency (PFFD) represents a rare and complex deformity manifested by hypoplasia of a variable portion of the femur with shortening of the entire limb. The condition may be unilateral or bilateral and is often associated with other congenital anomalies. Recent technological advances in ultrasound imaging offer the opportunity to detect an increasing number of rare skeletal malformation syndromes whose correct diagnosis is essential for adequate counseling and management of the pregnancy. We report a case of fetal non-familial PFFD diagnosed prenatally using two-dimensional and three-dimensional images. Clinical findings, differential diagnosis and management of this rare skeletal dysplasia are discussed and a review of the recent literature is given.

Prenatal sonographic diagnosis of skeletal dysplasias

OBJECTIVE

To assess the types and numbers of cases, gestational age at specific prenatal diagnosis and diagnostic accuracy of the diagnosis of skeletal dysplasias in a prenatal population from a single tertiary center.

METHODS

This was a retrospective database review of type, prenatal and definitive postnatal diagnoses and gestational age at specific prenatal diagnosis of all cases of skeletal dysplasias from a mixed referral and screening population between 1985 and 2007. Prenatal diagnoses were grouped into 'correct ultrasound diagnosis' (complete concordance with postnatal pediatric or pathological findings) or 'partially correct ultrasound diagnosis' (skeletal dysplasias found postnatally to be a different one from that diagnosed prenatally).

RESULTS

We included 178 fetuses in this study, of which 176 had a prenatal ultrasound diagnosis of 'skeletal dysplasia'. In 160 cases the prenatal diagnosis of a skeletal dysplasia was confirmed; two cases with skeletal dysplasias identified postnatally had not been diagnosed prenatally, giving 162 fetuses with skeletal dysplasias in total. There were 23 different classifiable types of skeletal dysplasia. The specific diagnoses based on prenatal ultrasound examination alone were correct in 110/162 (67.9%) cases and partially correct in 50/162 (30.9%) cases, (160/162 overall, 98.8%). In 16 cases, skeletal dysplasia was diagnosed prenatally, but was not confirmed postnatally (n = 12 false positives) or the case was lost to follow-up (n = 4). The following skeletal dysplasias were recorded: thanatophoric dysplasia (35 diagnosed correctly prenatally of 40 overall), osteogenesis imperfecta (lethal and non-lethal, 31/35), short-rib dysplasias (5/10), chondroectodermal dysplasia Ellis-van Creveld (4/9), achondroplasia (7/9), achondrogenesis (7/8), campomelic dysplasia (6/8), asphyxiating thoracic dysplasia Jeune (3/7), hypochondrogenesis (1/6), diastrophic dysplasia (2/5), chondrodysplasia punctata (2/2), hypophosphatasia (0/2) as well as a further 7/21 cases with rare or unclassifiable skeletal dysplasias.

CONCLUSION

Prenatal diagnosis of skeletal dysplasias can present a considerable diagnostic challenge. However, a meticulous sonographic examination yields high overall detection. In the two most common disorders, thanatophoric dysplasia and osteogenesis imperfecta (25% and 22% of all cases, respectively), typical sonomorphology accounts for the high rates of completely correct prenatal diagnosis (88% and 89%, respectively) at the first diagnostic examination.

Defective somitogenesis and abnormal vertebral segmentation in man

In recent years molecular genetics has revolutionized the study of somitogenesis in developmental biology and advances that have taken place in animal models have been applied successfully to human disease. Abnormal segmentation in man is a relatively common birth defect and advances in understanding have come through the study of cases clustered in families using DNA linkage analysis and candidate gene approaches, the latter stemming directly from knowledge gained through the study of animal models. Only a minority of abnormal segmentation phenotypes appear to follow Mendelian inheritance but three genes--DLL3, MESP2 and LNFG--have now been identified for spondylocostal dysostosis (SCD), a spinal malformation characterized by extensive hemivertebrae, trunkal shortening and abnormally aligned ribs with points of fusion. In affected families autosomal recessive inheritance is followed. These genes are all important components of the Notch signaling pathway. Other genes within the pathway cause diverse phenotypes such as Alagille syndrome (AGS) and CADASIL, conditions that may have their origin in defective vasculogenesis. This review deals mainly with SCD, with some consideration of AGS. Significant future challenges lie in identifying causes of the many abnormal segmentation phenotypes in man but it is hoped that combined approaches in collaboration with developmental biologists will reap rewards.

FGF signaling in the developing endochondral skeleton

Mutations in fibroblast growth factor receptors (Fgfrs) are the etiology of many craniosynostosis and chondrodysplasia syndromes in humans. The phenotypes associated with these human syndromes and the phenotypes resulting from targeted mutagenesis in the mouse have defined essential roles for FGF signaling in both endochondral and intramembranous bone development. In this review, I will focus on the role of FGF signaling in chondrocytes and osteoblasts and how FGFs regulate the growth and development of endochondral bone.

Fetal skeletal deformities - the diagnostic accuracy of prenatal ultrasonography and fetal magnetic resonance imaging

OBJECTIVE

To evaluate the diagnostic accuracy of prenatal ultrasonography and fetal magnetic resonance imaging (MRI) in fetuses with skeletal deformities (SD).

METHODS

Fourteen pregnant women of 21 - 34 weeks of gestation whose fetuses had SD on prenatal ultrasound (seven fetuses with spina bifida, four with complex malformation syndrome, two with scoliosis, and one with chondrodysplasia) were additionally investigated by fetal MRI using a 1.5T superconducting system with T1-and T2-weighted sequences in three section-planes. Main outcome measures were diagnostic accuracy, potential effect on parental counselling and influence on perinatal management of the additional investigation with fetal MRI.

RESULTS

In 10 cases ultrasound had a better diagnostic accuracy than MRI concerning the diagnosis of SD. In four cases with spina bifida MRI provided additional information towards preoperative evaluation for neurosurgery. In five cases parental counselling was improved. There was no influence on perinatal management.

CONCLUSION

MRI may provide additional information to ultrasound scan in fetuses with spina bifida and consecutive neurosurgery; in fetuses with other skeletal deformities additional information may be expected only in rare cases.

Prenatal assessment of normal fetal humerus volume by three-dimensional ultrasound

Because fetal humerus dysplasia is associated with a variety of congenital syndromes, prenatal assessment of the fetal humerus growth is very important. The fetal humerus volume is one of the indexes in evaluating the humerus growth, but it has never been studied by 3-D ultrasound (US) in utero. To establish a normal reference chart of the fetal humerus volume for clinical use, we undertook a prospective and cross-sectional study using 3-D US to assess the fetal humerus volume in normal pregnancy. A total of 216 singleton fetuses that ranged between 20 and 40 weeks of gestation and fit the criteria of normal pregnancies were included in this study. Our results showed that the fetal humerus volume is highly correlated with the gestational age (GA). Using GA as the independent variable and the humerus volume as the dependent variable, the best-fit regression equation was humerus volume (mL) = 0.0044GA(2) - 0.0841GA + 0.6874 (r = 0.97, n = 216, p < 0.0001). For clinical use, a chart of normal growth centiles of the fetal humerus volume was then established based on this equation. In addition, the common indexes of fetal biometry, such as biparietal diameter, occipitofrontal diameter, head circumference, abdominal circumference, femur length and estimated fetal weight, were all highly correlated with the humerus volume (all p < 0.0001). In conclusion, our data of the fetal humerus volume assessed by 3-D US can serve as a useful reference in evaluating the fetal humerus growth during normal gestation.

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.

Use of three-dimensional ultrasound imaging in the diagnosis of prenatal-onset skeletal dysplasias

OBJECTIVE

Recognition of prenatal-onset skeletal dysplasias has improved with advances in ultrasound imaging. Skeletal abnormalities can be recognized by two-dimensional (2D) ultrasound, but generating a precise diagnosis can be challenging. We aimed to determine whether three-dimensional (3D) imaging conferred any advantages over 2D imaging in these cases.

METHODS

We studied five women with fetuses of 16-28 gestational weeks referred for abnormal ultrasound skeletal findings. First 2D and then 3D sonography was performed and the results compared.

RESULTS

The pregnancies resulted in the following skeletal dysplasias: thanatophoric dysplasia, achondrogenesis II/hypochondrogenesis, achondroplasia, chondrodysplasia punctata (rhizomelic form) and Apert's syndrome. For all five fetuses, the correct diagnosis was made in the prenatal period by analysis of the 2D images. In each case the 3D images confirmed the preliminary diagnosis and for many findings it improved the visualization of the abnormalities.

CONCLUSION

The 3D imaging had advantages over the 2D imaging when it came to evaluation of facial dysmorphism, relative proportion of the appendicular skeletal elements and the hands and feet. Most importantly, the patient and referring physician appreciated the 3D images of the abnormal findings more readily which aided in counseling and management of the pregnancy.

Novel SOX9 expression during human pancreas development correlates to abnormalities in Campomelic dysplasia

Haploinsufficiency of SOX9, which encodes a homeodomain transcription factor, results in Campomelic dysplasia. Classical features of this disorder (e.g. skeletal dysplasia and 46,XY sex reversal) are in concordance with SOX9 expression profiles during human embryonic development. We report the robust expression of SOX9 throughout the pancreas during human embryogenesis, at levels of detection equivalent to the developing skeleton and testis. In the early foetal period, SOX9 expression declines and, in particular, is not apparent within the pancreatic islets. In keeping with this profile, examination of three cases with Campomelic dysplasia revealed abnormal pancreatic morphology. Epithelial cells were less densely packed within the mesenchymal stroma and islets less clearly formed with variable expression of hormone and beta cell markers. Taken together, these data indicate a novel potential role for SOX9 in pancreas development during human embryogenesis and early foetal life.

Development of the bones and synovial joints in the rat model of the VATER association

The adriamycin-induced rat model of the Vertebral, Anorectal, Tracheo-Esophageal, Radial and Renal (VATER) association produces a variety of vertebral, rib, and limb abnormalities. This study was designed to document accurately the nature of these abnormalities and to determine whether synovial joints are affected. Fetuses from pregnant Sprague Dawley rats that had received intraperitoneal injections of 1.75 mg/kg of adriamycin on days 6-9 or 10-13 of gestation were harvested. Double-stained skeletal preparations and histological sections were examined for vertebral, rib, and limb anomalies. The incidence of anomalies was high in the group treated on gestational days (GD) 6-9, while it was low in the GD 10-13 group. The length and thickness of the long bones were reduced, with bowing and reduction in their endochondral ossification. Sirenomelia occurred in the group treated on GD 6-9, and was often associated with a short tail and anal atresia. The joint cavities, and intra-articular structures such as menisci and the cruciate ligaments developed normally from the mesenchymal interzone. These data indicate that adriamycin inhibits skeletal growth and differentiation without any interference in the differentiation of the mesenchymal interzone, thus producing normal synovial joints.

Targeted disruption of the homeobox transcription factor Bapx1 results in lethal skeletal dysplasia with asplenia and gastroduodenal malformation

BACKGROUND

NK homeobox genes have been shown to play important roles in cell-type specification and organogenesis. Murine Bapx1, a member of NK homeobox gene family, is expressed in all the cartilageous tissues that undergo endochondral bone formation, and in gut mesentery during embryogenesis, suggesting that Bapx1 may be a key transcription factor ragulating the development of these organs.

RESULTS

We generated Bapx1-deficient mice by gene targeting. Bapx1-/- mice exhibited lethal skeletal dysplasia, with abnormal development of the vertebral column and some craniofacial bones, accompanied with asplenia and gastroduodenal malformation. We showed that the proliferative activity of the sclerotome cells, forming the vertebral column, was significantly reduced in Bapx1-/- embryos. The sclerotome cells of the mutants appeared to migrate and condense normally, but subsequent differentiation into the mature vertebral bodies and intervertebral discs were affected. The sclerotome cells in the vertebral bodies failed to differentiate into hypertrophic chondrocytes, as revealed by the undetected expression of Col10a1 and Osteopontin, and the sclerotome cells in the intervertebral discs failed to express the typical extracellular matrix proteins Col2a1, Col9a2 and aggrecan. Furthermore, we investigated the effect of loss of Bapx1 on the expression of some transcription factors, identified to be expressed in the developing sclerotome and be required for normal development of the vertebral column. Among them, we found that the expression of MFH-1 (mesenchyme forkhead-1), which was reported to regulate the proliferation and differentiation of sclerotome cells, was significantly reduced in ventromedial sclerotome cells in Bapx1-/- mice.

CONCLUSION

Our analysis provided evidence that Bapx1 was indispensable for normal development of ventromedial structure of vertebral column and some of craniofacial bones, splenogenesis and morphogenesis of gastroduodenal tract.

The scapula as a window to the diagnosis of skeletal dysplasias

Evaluation of the scapula can be useful in the diagnosis of skeletal dysplasias and helpful for the classification and delineation of new entities. A review of 2100 computerized cases of skeletal dysplasias in the International Skeletal Dysplasia Registry was performed. We found that the Luton type of platyspondylic lethal skeletal dysplasia differed radiographically from the San Diego type and Torrance type by the presence of two spikes at the inferior angle of the scapula. Hypoplasia of the body of the scapula, which is characteristic for campomelic dysplasia but not for kyphomelic dysplasia, is also present in Antley-Bixler syndrome. Radiographic and clinical similarities between campomelic dysplasia and Antley-Bixler syndrome suggest that they might be related disorders and that the latter condition should be included in the bent-bone dysplasia group. Similarity between the metaphyseal regions of the scapula and the metaphyses of the long tubular bones in the different types of short-rib polydactyly syndrome illustrates the importance of evaluation of the scapula in this group as well as in other well-defined or unknown osteochondrodysplasias.

Prenatal diagnosis of metatropic dwarfism

We present a case of prenatal diagnosis of severe metatropic dysplasia at 20 weeks' gestation. The characteristic prenatal features of this rare autosomal recessive chondrodysplasia appear to be significant dwarfism with an enlarged head and a narrow thorax associated with enlargement of the hands and feet, and the radiographic 'dumb-bell' appearance of the long bones.

Infantile type of Blount's disease: considerations concerning etiopathogenesis and treatment

The proper treatment of the infantile type of Blount's disease is still a controversial issue. We postulate the hypothesis of the etiopathogenesis of the infantile type of Blount's disease as a disease related to a dysplastic linkage between epiphysis and metaphysis. Therefore, considering the radiographic observations of a 26-month-old girl admitted in our department in 1986 with the infantile type of Blount's disease (type II Langenskiold--tibial femoral angle 24 degrees), the consequential optimal management of this condition is the need to apply a treatment consisting of the epiphyseal distraction capable of interrupting this dysplastic linkage, avoiding recurrences and damage to the growth cartilage. This child was treated with early, slow, and monocompartmental distraction by Ilizarov apparatus for 11 weeks. When the Ilizarov apparatus was removed, full recovery was achieved, the leg was clinically straight, and the mechanical axis was restored. The long-term follow-up (7 years) confirms this operation as a definitive treatment. It was less traumatic for the child, without recurrences or disorders of growth cartilage, supporting the dysplastic origin of infantile type of Blount's disease and the efficacy of this type of treatment.

The embryology of lower-extremity torsion

The presence of torsional deformities in the lower extremities of otherwise normal children is based on a variety of developmental processes. With intrauterine maturation, both rotation and external compression of the extremities take place. These forces result in the normal molding and final position of the limbs. Torsion of the extremities is, thus, a normal embryological process. It is imperative for the treating physician to understand these factors in human development to decide which cases are significant deviations from normal torsion. Knowledge of the embryology and natural history of these conditions is a key to appropriate treatment of patients with torsional or angular malalignments.

The prenatal development of the normal human skeleton: a combined ultrasonographic and post-mortem radiographic study

Post-mortem radiography of fetuses with skeletal dysplasia is essential for diagnostic classification. Interpretation of the radiographs should be based on the knowledge of morphology and dimensions of the normal skeleton in all stages of development. A retrospective post-mortem radiographic study is presented with measurements of the lengths of the long bones and thoracic and lumbar spine. The study included 69 fetuses and neonates with a normal skeleton, whose gestational age ranged from 13-42 weeks and who died perinatally or lived for less than one week. The measurements of the long bones were plotted on growth curves obtained from a prospective longitudinal ultrasonographic investigation of another group of 63 normal fetuses from 12-40 weeks of gestation. Thoracic and lumbar spine measurements by ultrasonography were not available. The radiographic data of thoracic and lumbar spine were, therefore, compared to radiographic studies from the literature. No disagreement with these studies was found. It can be concluded that measurements of bones from standardized post-mortem radiographs in cases of questionable gestational age or defects of bone development can be compared with ultrasonographic measurements. To illustrate the usefulness of the graphs, 13 fetuses with various types of skeletal dysplasia were evaluated retrospectively.

Achondrogenesis type II, abnormalities of extracellular matrix

Immune and lectin histochemical and microchemical methods were employed to study growth cartilage from seven cases of achondrogenesis type II (Langer-Saldino). The normal architecture of the epiphyseal and growth plate cartilage was replaced by a morphologically heterogeneous tissue. Some areas were comprised of vascular canals surrounded by extensive fibrous tissue and enlarged cells that had the appearance and histochemical characteristics of hypertrophic chondrocytes. Other areas contained a mixture of cells ranging from small to the enlarged chondrocytes. The extracellular matrix in the latter areas was more abundant and had characteristics of both precartilage mesenchymal matrix and typical cartilage matrix; it contained types I and II collagen, cartilage proteoglycan, fibronectin, and peanut agglutinin binding glycoconjugate(s). Peptide mapping of cyanogen bromide cartilage collagen peptides revealed the presence of types I and II collagen. These observations could be explained by a defect in the biosynthesis of type II collagen or in chondrocyte differentiation.

Hypertelorism and the median cleft face syndrome. An embryological analysis

A microscopical study of the early and late development of the face was performed in 77 human embryos and fetuses. After the transformation of both nasal placodes, via nasal grooves, into the nasal tubes the ectoderm of the face is closed superficially and the early development of the face (less than or equal to 17 mm crown-rump length (C-RL)) is terminated. Between the nasal tubes the internasal groove is present. Furthermore these embryos show physiologically a flat nose and hypertelorism. During the late development (greater than or equal to 17 mm C-RL) of the face the internasal groove disappears due to the outgrowth and differentiation of the nasal septum in the frontocaudal direction. Simultaneously (17-27 mm C-RL) the distance between the eyes decreases relatively, because of a relative lag in transverse growth. The differentiation of the facial mesenchyme into bone centres starts in the same period. From this embryological point of view the major anomalies of the median cleft face syndrome (hypertelorism--orbital as well as interorbital--and cranium bifidum occultum, median cleft nose, median cleft prolabium and median cleft premaxilla), can be classified as secondary or late, i.e., differentiation, defects.

Second trimester oligohydramnios, a predictor of poor fetal outcome

Twelve cases of severe second trimester oligohydramnios are reported. The outcome of these pregnancies was uniformly poor, with no survivors in the present series. Four patients had therapeutic abortions, one woman had spontaneous labor at 22 weeks' gestation, and seven patients continued to viability. Of these, five patients had severe renal abnormalities incompatible with life. Two infants died at, or shortly after, birth from severe intrauterine growth retardation (IUGR), one of which had a triploid karyotype. Review of the literature shows a similar poor outcome for pregnancies with severe oligohydramnios in the second trimester.

Regrowth of diastematomyelic bone spur after extradural resection. Case report

Complete regrowth of a diastematomyelic bone septum producing progressive neurological deficits was found in a 15-year-old boy who had a previous extradural resection of a similar bone spur with the dural sleeve left untouched. This case and two similar cases in the literature documenting continued neurological deterioration after extradural removal of septum emphasize the need for resection of the dural sleeve along with the bone septum if adequate relief of tethering is expected. The capability of the septum to regenerate may be due to the persistence of residual mesenchymal cells associated with the embryogenesis of the midline septum.

Ultrasonographic diagnosis of second-trimester skeletal dysplasias: a prospective analysis in a high-risk population

Sixteen pregnancies in 15 women at high genetic risk for having fetuses with skeletal dysplasias were examined by use of ultrasonography during the second trimester. In addition to the routine examination of fetal head and body, the fetal calvarium, spine, ribs, pelvis, and long bones were specifically evaluated for bone brightness, deformity, fractures, and inappropriate growth. It was determined that 11 of the 16 fetuses were normal and five were abnormal. At birth, all 11 ultrasonographically determined normal fetuses were normal, and at birth or elective termination of pregnancy the other five were abnormal. All abnormalities detected by ultrasonography in the affected fetuses were found at delivery, including decreased bone brightness, deformity of the head and long bones, and fractures and abnormal growth of the long bones. On the basis of this study, it is felt that ultrasonography is highly accurate for the diagnosis of many second-trimester skeletal dysplasias.

[Inherited disorders of the skeleton. Classification (author's transl)]

Based on the analysis of embryo development and genesis of the skeleton, author establishes two main groups of skeleton inherited disorders: 1) dysostosis due to alteration in morphogenesis, and 2) dysplasias due to the alteration of histogenesis.

Embryotoxic effects of magnesium deficiency and stress on rats and mice

Pregnant rats an mice received a magnesium (Mg)-deficient diet with different Mg contents from 40 t 360 ppm. The control received 2,000 ppm. At the end of gestation, the Mg concentration in the maternal serum was found to have decreased by up to 0.3 mmole/liter, depending on the Mg content of the food. Mg-dose-dependent embryotoxic effects (resorptions, retardation, disturbed bone development, and skeletal malformations) were observed only below a threshold value of 0.7 mmole/liter of the maternal serum Mg concentration. Noise stress in rats, in addition to a mild Mg deficiency (360 ppm Mg), which by itself had no effects, increased the rate of resorptions only.

Fertility, hatchability and malformations in guinea fowl embryos as affected by dietary manganese

1. The effects of feeding diets containing 54 mg, 60 mg, 65 mg or 70 mg manganese/kg to Guinea fowls on fertility, hatchability and the occurrence of malformed embryos were studied. 2. Dietary manganese affected fertility slightly, but significantly affected hatchability and the occurrence of malformed embryos. 3. Hatchability was most significantly depressed at the lowest dietary concentration of manganese, which also caused a highly significant increase in the proportion of malformed embryos. 4. Although increasing manganese to more than 54 mg/kg improved hatchability and reduced embryonic malformations, the increase did not completely eliminate the latter condition.

[Pathogenesis of skeletal radiation injuries to the proximal portion of the pelvic extremity in white rat embryos]

The mechanisms forming certain anomalies in the pelvic proximal part in the offspring of white rats subjected to x-ray radiation on the 12th and 13th days of gestation have been analysed. Serial sections of the embryos performed at various time after radiation and electron microscopic investigations have demonstrated that radiation lesions in the locomotor apparatus are of different pathogenesis. Defects in the femoral and pelvic bones, their fusion in the coxofemoral joint are anomalies resulted from destruction of some mesenchymal cells in the proximal part of the pelvic bud. Femoral dislocation, formed during gestation, is a result of disorders in coordinative muscle development, surrounding the joint and that of hypoplasia in the bursae-ligamentous apparatus (lack of head ligament, hypoplasia of the acetabular lip). Power disbalance in the muscles surrounding the joint is the main course resulting in dislocation of the femoral head.

[Cephalic neural crests and disorders of craniofacial morphogenesis. Neurocristopathies (author's transl)]

To establish the pathogenicity, and attempt to define a classification of craniofacial malformations is a difficult task, both in animals and humans. Mention is often made of the classification developed by Paul Tessier, which according to this author "is neither based on a theory nor on an embryonic definition. It is the by-product of anatomical findings during clinical examination and operative dissections" (31). The authors propose an embryologic classification of facial malformations, based on disorders of embryonic development of cells derived from the neural crests (NC) of cephalic origin, and constituting the craniofacial ectomesenchyme. The importance of the cephalic NC derivatives in craniofacial morphogenesis is stressed, and the principal malformations of the cephalic shelf outlined, as a function of disorders occurring during the formation of the NC; migrations, proliferation, and differentiation of their derivatives. The main objective of this study was to formulate pathogenetic hypotheses, to propose a classification, and to stimulate interest in further studies in the realm of physiological and pathological craniofacial morphogenesis.

Proximal femoral focal deficiency

Children with congenital focal deficiency of the proximal femur present many problems that are but rarely encountered by the individual surgeon who is thus unable to accumulate a wide experience. This paper reviews the literature and analyses the treatment of twenty-three cases at the Royal Children's Hospital, Melbourne, with the object of producing a rational plan of treatment. The management of instability of the hip, malrotation, inadequate proximal musculature and leg length inequality are separately considered for five grades of deficiency. Milder forms are amenable to subtrochanteric osteotomy to correct varus deformity. Exploration and grafting of the pseudarthrosis is indicated where progressive deformity develops. In the more severe deficiency, conservative management of the proximal bony defect provides a better result with an operation only rarely indicated. The gross leg length inequality may be most successfully overcome by Syme's amputation with subsequent fusion of the knee to create an above-knee amputee with an end-bearing stump allowing ready fitting of a prosthesis.

Congenital dysplasia of C2--6

Neural arch dysplasia of the cervical vertebrae is a rare occurrence. The authors present a case with dysplasia of cervical bodies and posterior arch elements at multiple levels. The embryogenesis of these anomalies is discussed.

Reflections upon the aetiology of congenital pseudarthrosis of the clavicle. With a note on cranio-cleido dysostosis

The cause of pseudarthrosis of the clavicle is obscure. Right-sidedness is an almost constant feature. We have proposed that the lesion is sometimes due to pressure upon the developing clavicle by the subclavian artery which is normally at a higher level on the right side. This may be accentuated in the presence of cervical ribs or unduly elevated first ribs, both of which we have observed in association with pseudarthrosis. We have also noted pseudarthrosis on the left side in association with dextrocardia (when the relative positions of the subclavian arteries are reversed) and in the presence of a large left cervical rib. We have speculated upon the nature of the clavicular defect in cranio-cleido dysostosis, in which disorder the first ribs are habitually elevated. A similar mechanism may be involved.