Prevalence of rib anomalies in normal Caucasian children and childhood cancer patients

Increased incidences of cervical ribs in deer indicate extinction risk

Mammals as a rule have seven cervical vertebrae, a number which remains remarkably conserved. Occasional deviations of this number are usually due to the presence of cervical ribs on the seventh vertebra, indicating a homeotic transformation from a cervical rib-less vertebra into a thoracic rib-bearing vertebra. These transformations are often associated with major congenital abnormalities or pediatric cancers (pleiotropic effects) that are, at least in humans, strongly selected against. Based on data from Late Pleistocene mammoths (Mammuthus primigenius) and woolly rhinoceroses (Coelodonta antiquitatis) from the North Sea, we hypothesized that high incidences of cervical ribs in declining populations are due to inbreeding and/or adverse conditions impacting early pregnancies. In this study, we investigated the incidence of cervical ribs in an extinct Late Pleistocene megaherbivore, giant deer (Megaloceros giganteus) from Ireland and in the extant highly inbred Père David deer (Elaphurus davidianus) and in twenty other extant species. We show that the incidence of cervical ribs is exceptionally high in both the Irish giant deer and the Père David deer and much higher than in extant outbred deer. Our data support the hypothesis that inbreeding and genetic drift increase the frequencies of maladaptive alleles in populations at risk of extinction. The high incidence of cervical ribs indicates a vulnerable condition, which may have contributed to the extinction of megaherbivore species in the Late Pleistocene. We argue that cervical rib frequency may be a good proxy for extinction risk in inbred populations.

Breaking the constraint on the number of cervical vertebrae in mammals: On homeotic transformations in lorises and pottos

Mammals almost always have seven cervical vertebrae. The strong evolutionary constraint on changes in this number has been broken in sloths and manatees. We have proposed that the extremely low activity and metabolic rates of these species relax the stabilizing selection against changes in the cervical count. Our hypothesis is that strong stabilizing selection in other mammals is largely indirect and due to associated pleiotropic effects, including juvenile cancers. Additional direct selection can occur due to biomechanical problems (thoracic outlet syndrome). Low metabolic and activity rates are thought to diminish these direct and indirect effects. To test this hypothesis within the primates, we have compared the number of cervical vertebrae of three lorisid species with particularly low activity and metabolic rates with those of more active primate species, including with their phylogenetically closest active relatives, the galagids (bushbabies). In support of our hypothesis, we found that 37.6% of the lorisid specimens had an abnormal cervical count, which is a higher percentage than in the other nine primate families, in which the incidence varied from zero to 2.2%. We conclude that our data support the importance of internal selection in constraining evolvability and of a relaxed stabilizing selection for increasing evolvability. Additionally, we discuss that there is no support for a role of the muscularized diaphragm in the evolutionary constraint.

Prevalence of cervical ribs and elongated transverse processes in Omani population: a computed tomography-based study

INTRODUCTION

Cervical ribs are the supernumerary ribs that usually arise from the seventh cervical vertebra. Ethnic and geographical variations in cervical ribs and elongated transverse processes have been reported. Therefore, we aimed to study the prevalence of cervical ribs and elongated transverse processes and morphometry of cervical ribs in Omani subjects using computed tomography (CT).

METHODS

A total of 1165 consecutive patients' CT scans of the cervical spine who had visited the tertiary care hospital from January 2016 to December 2020 were included in the study. The CT scans were screened for cervical ribs and elongated C7 transverse processes. Fisher's exact test was used to determine the gender influence.

RESULTS

Cervical ribs were identified in 0.94% of patients with a male-to-female ratio of 0.37:1. Most cervical ribs were unilateral (54%). The elongated C7 transverse process was identified in 18.45% of patients, with a male-to-female ratio of 1.36:1. Female patients are more likely to have cervical ribs (effect size = 5.98, 95% CI = 1.58-22.6, p = 0.005) than male patients. In contrast, the elongated C7 transverse process is more frequent in males (effect size = 1.82, 95% CI = 1.34-2.47, p < 0.001). The length and width of the cervical ribs are presented.

CONCLUSION

The prevalence of cervical ribs in Omani subjects is close to that of accepted prevalence worldwide. However, the elongated C7 transverse process prevalence is comparatively high and close to the Saudi population.

Diagnostic and Therapeutic Management of the Thoracic Outlet Syndrome. Review of the Literature and Report of an Italian Experience

The Thoracic Outlet Syndrome is a clinical potentially disabling condition characterized by a group of upper extremity signs and symptoms due to the compression of the neurovascular bundle passing through the thoracic outlet region. Because of the non-specific nature of signs and symptoms, to the lack of a consensus for the objective diagnosis, and to the wide range of etiologies, the actual figure is still a matter of debate among experts. We aimed to summarize the current evidence about the pathophysiology, the diagnosis and the treatment of the thoracic outlet syndrome, and to report a retrospective analysis on 324 patients followed for 5 years at the Padua University Hospital and at the Naples Fatebenefratelli Hospital in Italy, to verify the effectiveness of a specific rehabilitation program for the syndrome and to evaluate if physical therapy could relieve symptoms in these patients.

Proposed criteria for nevoid basal cell carcinoma syndrome in children assessed using statistical optimization

Nevoid basal cell carcinoma syndrome (NBCCS) is a tumor predisposition condition, the cardinal features of which emerge in adolescence or adulthood. Using statistical optimization, this study proposes NBCCS criteria with improved sensitivity in children less than 18 years of age. Earlier detection may lead to improved surveillance and prevention of sequelae. A survey eliciting medical history was completed by, or on behalf of, individuals with NBCCS. Based on these findings, criteria for suspicion of NBCCS in children were suggested using information from a Bernoulli naïve Bayes classifier relying on the human phenotype ontology. The sensitivity and specificity of the existing and proposed diagnostic criteria were also assessed. Participants (n = 48) reported their first signs of NBCCS appeared at a median age of 8 months, but by our retrospective analysis, they did not fulfill the current diagnostic criteria until a median age of 7 years. This study delineates the early-onset features of NBCCS and proposes criteria that should prompt consideration of NBCCS. Additionally, we demonstrate a method for quantitatively assessing the utility of diagnostic criteria for genetic disorders.

Exploring copy number variants in deceased fetuses and neonates with abnormal vertebral patterns and cervical ribs

Background

Cervical patterning abnormalities are rare in the general population, but one variant, cervical ribs, is particularly common in deceased fetuses and neonates. The discrepancy between the incidence in the general population and early mortality is likely due to indirect selection against cervical ribs. The cause for the co‐occurrence of cervical ribs and adverse outcome remains unidentified. Copy number variations resulting in gain or loss of specific genes involved in development and patterning could play a causative role.

Methods

Radiographs of 374 deceased fetuses and infants, including terminations of pregnancies, stillbirths and neonatal deaths, were assessed. Copy number profiles of 265 patients were determined using single nucleotide polymorphism array.

Results

274/374 patients (73.3%) had an abnormal vertebral pattern, which was associated with congenital abnormalities. Cervical ribs were present in 188/374 (50.3%) and were more common in stillbirths (69/128 [53.9%]) and terminations of pregnancies (101/188 [53.7%]), compared to live births (18/58, 31.0%). Large (likely) deleterious copy number variants and aneuploidies were prevalent in these patients. None of the rare copy number variants were recurrent or overlapped with candidate genes for vertebral patterning.

Conclusions

The large variety of copy number variants in deceased fetuses and neonates with similar abnormalities of the vertebral pattern probably reflects the etiological heterogeneity of vertebral patterning abnormalities. This genetic heterogeneity corresponds with the hypothesis that cervical ribs can be regarded as a sign of disruption of critical, highly interactive stages of embryogenesis. The vertebral pattern can probably provide valuable information regarding fetal and neonatal outcome.

Miscarriage is associated with cervical ribs in thoracic outlet syndrome patients

The constancy of the number of cervical vertebrae in mammals is probably the result of selection against associated variations. A survey among patients with and without cervical ribs showed an association between miscarriage and the presence of cervical ribs. This supports the hypothesized selection against variations in cervical vertebral number.

Cervical ribs in human early life: morphological variability and first identification as a morbidity criterion in a past population

Despite the medical literature on supernumerary cervical ribs in extant adult samples, little is known about their development and occurrence in early infancy. The documentation of cervical ribs in modern samples of fetuses and neonates is indeed affected by ethical as well as technical limitations. The aim of the present study was to investigate their frequencies and morphological variability in the first known archaeological collection of very young children with this anatomical variant. The study sample comes from the 8B-51 necropolis on the Saï island (Sudan) and dates to the Classic Kerma Period (XVIIIe-XVIe centuries BC). It consists of 64 individuals deceased between 24 weeks of amenorrhoea and 2 years of age. Bilateral or unilateral cervical ribs were found in 27 individuals. A total of 43 cervical ribs were identified, 38 of which are fully preserved. According to these observations, at least 42% of the individuals have unilateral or bilateral cervical ribs, with an average maximum length of < 1 cm. This frequency is very high compared to those observed in contemporary adult samples (up to 3%). First, the comparison of our results with biological and genetic research demonstrating the link between the occurrence of cervical ribs and a reduced chance of survival during infancy allows the first identification of this trait as an indicator of morbidity in an archaeological collection, a morbidity to which a genetic homogeneity or even endogamy could contribute. Second, the number of ribs studied makes it possible to propose a morphological classification based on the general shape and the shape of the articular facets, classification that can be used tos refine the analyses of the trait in future samples.

Cervical ribs and other abnormalities of the vertebral pattern in children with esophageal atresia and anorectal malformations

BACKGROUND

In mammals the vertebral column has a constant pattern, particularly in the cervical region, which is likely the result of stabilizing selection. The prevalence of cervical ribs and extended vertebral pattern abnormalities is increased in deceased fetuses and neonates and associated with structural and chromosomal anomalies. The hypothesized close interaction between vertebral patterning and organogenesis in early embryogenesis could be studied in children with esophageal atresia and anorectal malformations by evaluating the radiographs of the vertebral column and the type and number of associated anomalies METHODS: The vertebral pattern of 367 children diagnosed with an esophageal atresia (n = 135), anorectal malformation (n = 215), or both (n = 17) was assessed on radiographs.

RESULTS

The vertebral pattern was abnormal in 170/202 (84.2%) children in whom this could be assessed, and cervical ribs were present in 147/335 (43.9%). Extended vertebral pattern abnormalities became more frequent with an increasing number of associated structural abnormalities. Cervical ribs were particularly common in children with chromosomal and genetic abnormalities (18/20, 90.0%).

CONCLUSIONS

Cervical ribs are frequent and abnormal vertebral patterns are more extended in the presence of associated anomalies. These findings support the hypothesized selection against vertebral patterning variations and emphasize the relevance of assessment of the vertebral pattern.

Risk factors for childhood and adult primary brain tumors

Primary brain tumors account for ~1% of new cancer cases and ~2% of cancer deaths in the United States; however, they are the most commonly occurring solid tumors in children. These tumors are very heterogeneous and can be broadly classified into malignant and benign (or non-malignant), and specific histologies vary in frequency by age, sex, and race/ethnicity. Epidemiological studies have explored numerous potential risk factors, and thus far the only validated associations for brain tumors are ionizing radiation (which increases risk in both adults and children) and history of allergies (which decreases risk in adults). Studies of genetic risk factors have identified 32 germline variants associated with increased risk for these tumors in adults (25 in glioma, 2 in meningioma, 3 in pituitary adenoma, and 2 in primary CNS lymphoma), and further studies are currently under way for other histologic subtypes, as well as for various childhood brain tumors. While identifying risk factors for these tumors is difficult due to their rarity, many existing datasets can be leveraged for future discoveries in multi-institutional collaborations. Many institutions are continuing to develop large clinical databases including pre-diagnostic risk factor data, and developments in molecular characterization of tumor subtypes continue to allow for investigation of more refined phenotypes. Key Point 1. Brain tumors are a heterogeneous group of tumors that vary significantly in incidence by age, sex, and race/ethnicity.2. The only well-validated risk factors for brain tumors are ionizing radiation (which increases risk in adults and children) and history of allergies (which decreases risk).3. Genome-wide association studies have identified 32 histology-specific inherited genetic variants associated with increased risk of these tumors.

Clinical, electrodiagnostic and imaging features of true neurogenic thoracic outlet syndrome: Experience at a tertiary referral center

OBJECTIVE

True neurogenic thoracic outlet syndrome (TN-TOS) is an extremely rare neuromuscular disease. We report clinical, electrodiagnostic and radiologic features of patients with TN-TOS.

METHODS

Retrospective chart review of patients satisfying criteria was done. Nerve conduction study (NCS) and needle electromyography (EMG) of upper extremity were reviewed. Brachial plexus MRI and computed tomography angiography (CTA) were also reviewed.

RESULTS

Thirteen TN-TOS patients were identified. The most common neurologic signs were hypesthesia in the medial forearm or ulnar digits and weakness of the abductor pollicis brevis (APB) muscle. In NCS, medial antebrachial cutaneous (MABC) sensory nerve action potential amplitude was decreased in all tested patients. The APB muscle was most commonly involved in EMG. Among radiologic criteria, focal stenosis of subclavian artery in CTA was the most common finding.

CONCLUSION

We confirmed that TN-TOS is T1 predominant lower roots/trunk brachial plexopathy with clinical and electrodiagnostic features. Radiologic studies may be used to detect structural abnormalities.

SIGNIFICANCE

As MABC NCS showed abnormal results in all tested patients, it should be added to electrodiagnostic study as screening method. If present, structural abnormalities might be confirmed with radiologic studies.

Prenatal Incidence and Clinical Value of the Absence of 12th Ribs in a Population in a Setting of Detailed Second-Trimester Sonography

OBJECTIVES

We aimed to determine the incidence of the absence of the (last) 12th ribs in a population in a setting of detailed 2nd-trimester sonography using three-dimensional (3D) ultrasound and to assess whether or not this may be related to chromosomal aneuploidies.

METHODS

Prospectively, we counted fetal ribs for the absence of the (last) 12th ribs in singleton pregnancies of women who presented to our clinic for detailed 2nd-trimester sonography. The assessment was carried out using 3D ultrasound. Volume data sets were acquired with the 3D skeleton mode using the maximum intensity with X-ray-weighted rendering. If the 3D skeleton mode was not sufficient, volume contrast imaging with the OmniView bone mode was used.

RESULTS

The fetal ribs could be visualized in 97.01% of the 1,943 fetuses examined between 20 and 23 weeks' gestation. Timing the examination at 21, 22, or 23 weeks was found to be more successful than conducting it at 20 weeks. Twelfth ribs were found to be absent in 33 fetuses; 16 fetuses had 11 ribs unilaterally and 17 had so bilaterally. None of them had chromosomal abnormalities. Associated anomalies were present in 6 fetuses (18.2%); 2 of the anomalies were major and 4 minor.

CONCLUSION

The incidence of absent 12th ribs in this mixed population was 1.75%. In the absence of additional anomalies, the prognosis is favorable.

Prenatal diagnosis of cervical ribs by three-dimensional ultrasound in a foetus with a herniated Dandy-Walker cyst

We present a case report of a foetus with a herniated Dandy-Walker cyst and bilateral rudimentary cervical ribs. The cervical ribs were visualised prenatally by three-dimensional ultrasound and confirmed by post-termination radiography. The prevalence of cervical ribs is higher in deceased fetuses and neonates with or without structural abnormalities compared with healthy individuals and might be regarded as a marker of disadvantageous fetal development. We demonstrate that evaluation of the fetal vertebral pattern by three-dimensional ultrasonography, including the cervical region, is feasible and could provide valuable information regarding fetal and neonatal prognosis.

Bone development in laboratory mammals used in developmental toxicity studies

Evaluation of the skeleton in laboratory animals is a standard component of developmental toxicology testing. Standard methods of performing the evaluation have been established, and modification of the evaluation using imaging technologies is under development. The embryology of the rodent, rabbit, and primate skeleton has been characterized in detail and summarized herein. The rich literature on variations and malformations in skeletal development that can occur in the offspring of normal animals and animals exposed to test articles in toxicology studies is reviewed. These perturbations of skeletal development include ossification delays, alterations in number, shape, and size of ossification centers, and alterations in numbers of ribs and vertebrae. Because the skeleton is undergoing developmental changes at the time fetuses are evaluated in most study designs, transient delays in development can produce apparent findings of abnormal skeletal structure. The determination of whether a finding represents a permanent change in embryo development with adverse consequences for the organism is important in study interpretation. Knowledge of embryological processes and schedules can assist in interpretation of skeletal findings.

Increased prevalence of abnormal vertebral patterning in fetuses and neonates with trisomy 21

PURPOSE

To assess the prevalence of an abnormal number of ribs in a cohort of fetuses and neonates with trisomy 21 and compare this with a subgroup of fetuses without anomalies.

MATERIALS AND METHODS

Radiographs of 67 deceased fetuses, neonates, and infants that were diagnosed with trisomy 21 were reviewed. Terminations of pregnancy were included. The control group was composed of 107 deceased fetuses, neonates, and infants without known chromosomal abnormalities, structural malformations, infections or placental pathology. Cases in which the number of thoracic ribs or presence of cervical ribs could not be reliably assessed were excluded. The literature concerning vertebral patterning in trisomy 21 cases and healthy subjects was reviewed.

RESULTS

Absent or rudimentary 12th thoracic ribs were found in 26/54 (48.1%) cases with trisomy 21 and cervical ribs were present in 27/47 (57.4%) cases. This prevalence was significantly higher compared to controls (28/100, 28.0%, Χ²(1) = 6.252, p = .012 and 28/97, 28.9%, Χ²(1) = 10.955, p < .001, respectively).

CONCLUSIONS

Rudimentary or absent 12th thoracic ribs and cervical ribs are significantly more prevalent in deceased fetuses and infants with trisomy 21.

Cervical Rib Prevalence and its Association with Thoracic Outlet Syndrome: A Meta-Analysis of 141 Studies with Surgical Considerations

BACKGROUND

Cervical ribs (CR) are supernumerary ribs that arise from the seventh cervical vertebra. In the presence of CR, the boundaries of the interscalene triangle can be further constricted and result in neurovascular compression and thoracic outlet syndrome (TOS). The aim of our study was to provide a comprehensive evidence-based assessment of CR prevalence and their association with TOS as well as surgical approach to excision of CR and surgical patients' characteristics.

METHODS

A thorough search of major electronic databases was conducted to identify any relevant studies. Data on the prevalence, laterality, and side of CR were extracted from the eligible studies for both healthy individuals and patients with TOS. Data on the type of TOS and surgical approach to excision of CR were extracted as well.

RESULTS

A total of 141 studies (n = 77,924 participants) were included into the meta-analysis. CR was significantly more prevalent in patients with TOS than in healthy individuals, with pooled prevalence estimates of 29.5% and 1.1%, respectively. More than half of the patients had unilateral CR in both the healthy and the TOS group. The analysis showed that 51.3% of the symptomatic patients with CR had vascular TOS, and 48.7% had neurogenic TOS. Most CR were surgically excised in women using a supraclavicular approach.

CONCLUSIONS

CR ribs are frequent findings in patients with TOS. We recommended counseling asymptomatic patients with incidentally discovered CR on the symptoms of TOS, so that if symptoms develop, the patients can undergo prompt and appropriate workup and treatment.

High incidence of cervical ribs indicates vulnerable condition in Late Pleistocene woolly rhinoceroses

Mammals as a rule have seven cervical vertebrae, a number that remains remarkably constant. Changes of this number are associated with major congenital abnormalities (pleiotropic effects) that are, at least in humans, strongly selected against. Recently, it was found that Late Pleistocene mammoths (Mammuthus primigenius) from the North Sea have an unusually high incidence of abnormal cervical vertebral numbers, approximately ten times higher than that of extant elephants. Abnormal numbers were due to the presence of large cervical ribs on the seventh vertebra, indicating a homeotic change from a cervical rib-less vertebra into a thoracic rib-bearing vertebra. The high incidence of cervical ribs indicates a vulnerable condition and is thought to be due to inbreeding and adverse conditions that may have impacted early pregnancies in declining populations. In this study we investigated the incidence of cervical ribs in another extinct Late Pleistocene megaherbivore from the North Sea and the Netherlands, the woolly rhinoceros (Coelodonta antiquitatis). We show that the incidence of abnormal cervical vertebral numbers in the woolly rhinoceros is unusually high for mammals (15,6%, n = 32) and much higher than in extant Rhinoceratidae (0%, n = 56). This indicates that woolly rhinoceros lived under vulnerable conditions, just like woolly mammoths. The vulnerable condition may well have contributed to their eventual extinction.

Pediatric cancer risk in association with birth defects: A systematic review

BACKGROUND

Many epidemiological studies have examined associations between birth defects (BDs) and pediatric malignancy over the past several decades. Our objective was to conduct a systematic literature review of studies reporting on this association.

METHODS

We used librarian-designed searches of the PubMed Medline and Embase databases to identify primary research articles on pediatric neoplasms and BDs. English language articles from PubMed and Embase up to 10/12/2015, and in PubMed up to 5/12/2017 following an updated search, were eligible for inclusion if they reported primary epidemiological research results on associations between BDs and pediatric malignancies. Two reviewers coded each article based on the title and abstract to identify eligible articles that were abstracted using a structured form. Additional articles were identified through reference lists and other sources. Results were synthesized for pediatric cancers overall and for nine major pediatric cancer subtypes.

RESULTS

A total of 14,778 article citations were identified, of which 80 met inclusion criteria. Pediatric cancer risk was increased in most studies in association with BDs overall with some notable specific findings, including increased risks for CNS tumors in association with CNS abnormalities and positive associations between rib anomalies and several pediatric cancer types.

CONCLUSIONS

Some children born with BDs may be at increased risk for specific pediatric malignancy types. This work provides a foundation for future investigations that are needed to clarify specific BD types predisposing toward malignancy and possible underlying causes of both BDs and malignancy.

Thoracic Outlet Syndrome: A Significant Family Genetic Phenotypic Presentation

We report on a very rare case of diagnosis and successful surgical treatment of three young family members with a four-fold presentation of thoracic outlet syndrome. In the relevant family case, we are considering and discussing the population incidence, a possible HOX genes disorder, and a significant phenotypic presentation.

Frederik Ruysch (1638-1731): Historical perspective and contemporary analysis of his teratological legacy

The Peter the Great Museum of Anthropology and Ethnography (Kunstkamera) in Saint Petersburg is the oldest museum in Russia. It keeps the remains of the anatomical collection of the world-famous 17th century Dutch anatomist Frederik Ruysch. This unique collection was bought and shipped in 1717 by Czar Peter the Great, and presently still comprises more than 900 specimens, a modest number of which concerns specimens with congenital anomalies. We searched for teratological clues in the existing collection and in all his descriptions and correspondence regarding specimens and cases he encountered during his career as doctor anatomiae and chief instructor of the surgeons and midwives in Amsterdam. A total of 63 teratological specimens and case descriptions were identified in this legacy, including some exceedingly rare anomalies. As it turns out, Ruysch was the first to describe several of the conditions we encountered, including intracranial teratoma, enchondromatosis, and Majewski syndrome. Although his comments pose an interesting view on how congenital anomalies were scientifically perceived in early 18th century Europe, Ruysch mostly refrained from explaining the causes of the conditions he encountered. Instead, he dedicated himself to careful descriptions of his specimens. Almost 300 years after his demise, Ruysch's legacy still impresses and inspires both scientists and lay men. © 2016 The Authors. American Journal of Medical Genetics Part A Published by Wiley Periodicals, Inc.

The Epidemiological, Morphological, and Clinical Aspects of the Cervical Ribs in Humans

A familiarity with the anatomy of some types of bone anomalies is necessary for clinicians involved in many medical areas. The aim of this paper is to review the newest literature concerning the morphology, embryology, clinical image, and therapeutic methods of the cervical ribs in the humans. The incidence of cervical ribs has been found to vary from 0.58% in Malaysian population to 6.2% in Turkish population. Cervical ribs have clinical implications that are generally divided into neurological or vascular. This study is of particular importance for clinicians, as early identification of cervical ribs may prevent life-threatening complications.

Paleodysmorphology and paleoteratology: Diagnosing and interpreting congenital conditions of the skeleton in anthropological contexts

Most congenital conditions have low prevalence, but collectively they occur in a few percent of all live births. Congenital conditions are rarely encountered in anthropological studies, not least because many of them have no obvious effect on the skeleton. Here, we discuss two groups of congenital conditions that specifically affect the skeleton, either qualitatively or quantitatively. Skeletal dysplasias (osteochondrodysplasias) interfere with the histological formation, growth and maturation of skeletal tissues leading to diminished postural length, but the building plan of the body is unaffected. Well- known skeletal dysplasias represented in the archeological record include osteogenesis imperfecta and achondroplasia. Dysostoses, in contrast, interfere with the building plan of the body, leading to e.g. missing or extraskeletal elements, but the histology of the skeletal tissues is unaffected. Dysostoses can concern the extremities (e.g., oligodactyly and polydactyly), the vertebral column (e.g., homeotic and meristic anomalies), or the craniofacial region. Conditions pertaining to the cranial sutures, i.e., craniosynostoses, can be either skeletal dysplasias or dysostoses. Congenital conditions that are not harmful to the individual are known as anatomical variations, several of which have a high and population-specific prevalence that could potentially make them useful for determining ethnic origins. In individual cases, specific congenital conditions could be determinative in establishing identity, provided that ante-mortem registration of those conditions was ensured. Clin. Anat. 29:878-891, 2016. © 2016 The Authors Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

Imaging of the Patient with Thoracic Outlet Syndrome

Patients with symptoms from compression of the neurovascular bundle in the thoracic outlet are described as having thoracic outlet syndrome (TOS), which is best thought of as three conditions classified according to which structures are involved. The purpose of this article is to review the role of imaging in evaluation of patients with TOS, beginning with diagnosis and extending through postoperative management. While diagnosis of TOS still rests on the patient's presenting history and physical examination, imaging examinations are helpful in supporting the diagnosis, delineating abnormal anatomy, determining which structures are compressed, identifying the site of compression, and excluding other diagnoses. Magnetic resonance imaging is the noninvasive imaging modality of choice in evaluating patients with suspected TOS, but computed tomography also plays an important role, particularly in delineating bone anatomy. Evidence of vascular damage is required to make the diagnosis of TOS at imaging. Dynamic compression of the axillosubclavian vessels at the thoracic outlet can be a finding supportive of the diagnosis of TOS but is not a stand-alone diagnostic criterion, as it can be seen in patients without TOS. As diagnosis and treatment of TOS increase, radiologists will increasingly encounter the TOS patient after decompression surgery. Recognition of the expected postoperative appearance of these patients is critical, as is an understanding of the imaging findings of potential short- and long-term complications. (©)RSNA, 2016.

Prevalence of C7 level anomalies at the C7 level: an important landmark for cervical nerve ultrasonography

BACKGROUND

Recently, various examination and intervention techniques using cervical nerve ultrasonography have been developed. The specific shapes of the C7 transverse process and vertebral artery in front of the C7 transverse process have become landmarks.

PURPOSE

To determine the prevalence of anomalies and anomalous vertebral artery entrances at the C7 transverse process.

MATERIAL AND METHODS

The records of patients who underwent plain or contrast-enhanced neck or cervical spine computed tomography (CT) were reviewed. The examinations were scored for the anomalous presence of anterior tubercles or cervical ribs as well as vertebral artery entrances in the C7 transverse process. The prevalence of anomalies was compared based on patient sex and age.

RESULTS

Evaluating the examinations from 2067 patients (1046 men; 1021 women), 1% of patients exhibited an anomalous presence of anterior tubercles, and 0.3% of patients displayed cervical ribs at the C7 transverse process. The prevalence of anomalies process was significantly higher in men aged less than 40 years than in older men (P < 0.001), whereas the prevalence was not higher in women aged less than 40 years than in older women. The prevalence of vertebral artery entry into the C7 transverse foramen was 0.6%.

CONCLUSION

Although an anomalous vertebral artery entry into the C7 transverse foramen was rare, the prevalence of an anomaly at the C7 transverse process was higher in men aged less than 40 years. Therefore, we recommend performing CT in younger men before cervical nerve ultrasonographic intervention to avoid misinterpretations at the cervical level.

Bone single-photon emission computed tomography and three-dimensional computed tomography in the diagnosis of low costal variation and pathologies

In general, there are five lumbar vertebras in normal human subjects. But occasionally there are six. In such a situation, a radiologist need to discern between lumbarization of S1 (S1 vertebra becomes segmented and mimics L5) or due to hypoplastic 12(th) ribs, hence the T12 vertebra is wrongly assumed to be L1. These interesting images serve a multimodality approach to right aplasia/left hypoplasia of 12(th) rib, injury of left 11(th) rib and subluxation of left 11(th) Costovertebral joint in a patient with lumbar back pain.

Extraordinary incidence of cervical ribs indicates vulnerable condition in Late Pleistocene mammoths

The number of cervical vertebrae in mammals is highly conserved at seven. We have shown that changes of this number are selected against due to a coupling with major congenital abnormalities (pleiotropic effects). Here we show that the incidence of abnormal cervical vertebral numbers in Late Pleistocene mammoths from the North Sea is high (33.3%) and approximately 10 times higher than that of extant elephants (3.6%). Abnormal numbers were due to the presence of large cervical ribs on the seventh vertebra, which we deduced from the presence of rib articulation facets on sixth (posterior side) and seventh (anterior side) cervical vertebrae. The incidence of abnormal cervical vertebral numbers in mammoths appears to be much higher than in other mammalian species, apart from exceptional sloths, manatees and dugongs and indicates a vulnerable condition. We argue that the increased incidence of cervical ribs in mammoths is probably caused by inbreeding and adverse conditions that impact early pregnancies in declining populations close to extinction in the Late Pleistocene.

[Minor phenotypic variants in patients with acute lymphoblastic leukemia from west Mexico]

INTRODUCTION

Acute lymphoblastic leukemia (ALL) has been associated with an excess of minor phenotypic variants (MPV), including common variants and minor anomalies, indicative of an altered phenogenesis. The objective of the study was to determine the association between MPV and ALL.

PATIENTS AND METHODS

In a hospital based case-control study, we studied 120 children with ALL (including standard and high risk) and 120 healthy children as a control group, matched for age and sex, seen in the Hospital Civil de Guadalajara Dr. Juan I. Menchaca (Guadalajara, Mexico). In both groups, 28 anthropometric measurements were made, as well as a systematic search for 405 MPV, through a physical examination. Adjusted odds ratio was estimated (aOR) with its intervening variables by logistic regression. The confidence interval was 95% (95%CI).

RESULTS

Anthropometric signs associated with ALL were: long upper segment (aOR= 2.19, 95%CI: 1.01-4.76), broad jaw (aOR= 2.62, 95%CI: 1.29-5.30), narrow ears (aOR= 6.22, 95%CI: 2.60-14.85), and increase in internipple distance (aOR= 2.53, 95%CI: 1.07-5.98). The hypoplasia mesofacial, broad forehead, small nose, short columella, narrow ears, telethelia, Sydney crease (SC), Greek type feet and café-au-lait spots (CALS), had a 3 to 17 times higher frequency in children with ALL. By number, an association was found from ≥4 MPV (aOR= 2.14, 95%CI: 1.25-3.66, P=.004).

CONCLUSIONS

From ≥4 MPV, an association was found with ALL, suggesting prenatal factors in phenogenesis and leukemogenesis. CALS and SC were confirmed as MPV in children with ALL.

Historical perspective on developmental concepts and terminology

In their ontogeny and phylogeny all living beings are historical entities. The revolution in biology of the 18th and 19th centuries that did away with the scala naturae according to which we humans, the acme of creation, "made a little lower than the angels," also led to the gradual realization that a humble one-celled protist ("protoctist"), such as Entamoeba histolytica of ill repute [Margulis and Chapman, ] has the same 4-billion-year phylogeny as that of Homo sapiens, vivid testimony to common ancestry and the relatedness of all living beings on earth. The group of medical geneticists who assembled at the NIH, Bethesda, MD this January to address terms pertaining to human ontogeny, did so in the long tradition of Sydenham, Linnaeus, Meckel, Geoffroy St-Hilaire père et fils, Wilhelm His and so many others before who had over the previous two centuries wrestled as earnestly as they could with concepts of "classification" and nomenclature of developmental anomalies. The prior massive need for classification per se in medical morphology has diminished over the years in favor of ever more sophisticated understanding of pathogenesis and cause through experimental biology and genetics; however, in the winter of 2013 it was still found prudent to respect terminological precedent on general terms while recognizing recent advances in developmental pathology requiring clarification and definition of special terms. Efforts along similar lines instigated by the German Society of Anatomists at their first meeting in Leipzig in 1887 culminated, after intense years of work by hundreds of experts and consultants under the goad of Wilhelm His, in the Basel Nomina Anatomica [BNA, His (1895)]. His, himself, stated prefatorily that the BNA had no legislative weight, only an evanescent consensus of many to be amended in the future as needed and indicated. Without hubris, no one before or after will do the same. The more substantial the consensus the more permanent the structure. After some 120 years the BNA is alive and flourishing. Now retitled Terminologia Anatomica, it has been amended and added to many times, is still in Latin but now with synonyms in English, the new lingua franca of science, for every anatomical, histological and embryological term. May our successors be equally effective.

Cervical ribs: identification on MRI and clinical relevance

To determine the prevalence of cervical ribs on cervical spine MRI and clinical relevance, we reviewed 2500 studies for cervical ribs and compression of neurovascular structures and compared to CT, when available. Brachial plexus or subclavian artery contact by cervical rib was identified on MRI and/or CT in 12 cases with diagnosis of thoracic outlet syndrome in one. Cervical ribs were identified on 1.2% (25/2083) of examinations, lower than on CT (2%), but MRI may offer equivalent anatomic explanation for patient symptoms.

Fertility treatments, congenital malformations, fetal loss, and childhood acute leukemia: the ESCALE study (SFCE)

BACKGROUND

This study investigated the relationships between childhood acute leukemia (AL) and selective maternal and birth characteristics, including congenital malformations and the use of fertility treatment, for which the literature remains scarce.

PROCEDURE

The national registry-based case-control study ESCALE was carried out in France in 2003-2004. Population controls were frequency matched with cases on age and gender. Data were obtained from structured telephone questionnaires. Odds ratios (OR) and their 95% confidence intervals were estimated using unconditional regression models adjusted for potential confounders.

RESULTS

In all, 764 cases of AL (648 lymphoblastic AL (acute lymphoblastic leukemia, ALL) and 101 myeloblastic AL) and 1,681 controls were included. The AL cases' mothers reported congenital malformations more frequently than the controls' mothers (OR = 1.5 [1.0-2.4]). ALL was significantly associated with the use of fertility treatment for the index pregnancy (OR = 1.9 [1.3-2.8]). In particular, ALL was associated with ovulation induction only (OR = 2.6 [1.6-4.3]), but not with in vitro fertilization (IVF, OR = 1.0 [0.4-2.3]) or artificial insemination (OR = 1.3 [0.5-3.9]). A positive association was also observed for the difficulty of becoming pregnant without fertility treatment (OR = 1.5 [1.0-2.1]). AL was positively associated with a history of voluntary abortion (OR = 1.4 [1.1-1.8]) but not with a history of spontaneous (OR = 0.8 [0.7-1.0]) or therapeutic (OR = 0.7 [0.5-1.1]) abortion.

CONCLUSION

The results suggest that subfertility in itself and ovulation induction may be associated with ALL, and support a positive association with congenital malformations. The links with the various types of fertility drugs and the underlying causes of infertility need to be investigated further.

Evo-Devo of the Human Vertebral Column: On Homeotic Transformations, Pathologies and Prenatal Selection

Homeotic transformations of vertebrae are particularly common in humans and tend to come associated with malformations in a wide variety of organ systems. In a dataset of 1,389 deceased human foetuses and infants a majority had cervical ribs and approximately half of these individuals also had missing twelfth ribs or lumbar ribs. In ~10 % of all cases there was an additional shift of the lumbo-sacral boundary and, hence, homeotic transformations resulted in shifts of at least three vertebral boundaries. We found a strong coupling between the abnormality of the vertebral patterns and the amount and strength of associated malformations, i.e., the longer the disturbance of the vertebral patterning has lasted, the more associated malformations have developed and the more organ systems are affected. The germ layer of origin of the malformations was not significantly associated with the frequency of vertebral patterns. In contrast, we find significant associations with the different developmental mechanisms that are involved in the causation of the malformations, that is, segmentation, neural crest development, left-right patterning, etc. Our results, thus, suggest that locally perceived developmental signals are more important for the developmental outcome than the origin of the cells. The low robustness of vertebral A-P patterning apparent from the large number of homeotic transformations is probably caused by the strong interactivity of developmental processes and the low redundancy of involved morphogens during early organogenesis. Additionally, the early irreversibility of the specification of the A-P identity of vertebrae probably adds to the vulnerability of the process by limiting the possibility for recovery from developmental disturbances. The low developmental robustness of vertebral A-P patterning contrasts with a high robustness of the A-P patterning of the vertebral regions. Not only the order is invariable, also the variation in the number of vertebrae per region is small. This robustness is in agreement with the evolutionary stability of vertebral regions in tetrapods. Finally, we propose a new hypothesis regarding the constancy of the presacral number of vertebrae in mammals.

Cervical ribs: a common variant overlooked in CT imaging

BACKGROUND AND PURPOSE

Cervical ribs are congenital variants that are known to cause TOS or brachial plexopathy in up to 10% of the affected individuals. We investigated how often cervical ribs are present on cervical spine CT scans to determine the incidence in humans and the percentage of reported cervical ribs.

MATERIALS AND METHODS

Cervical spine CT scans and the reports of 3404 consecutive adult patients were retrospectively reviewed to determine the presence of cervical ribs and whether they had been reported.

RESULTS

Cervical ribs were found in 2.0% (67/3404) of the population. Of the 67 patients with cervical ribs, 27 (40.3%) had bilateral ribs. The prevalence of cervical ribs in women was twice that in men, 2.8% (39/1414) versus 1.4% (28/1990). Although African Americans accounted for 50.1% (1706/3404) and whites, 41.2% (1402/3404) of the patient population, African Americans were 70.1% (47/67) of patients with cervical ribs, whereas whites were 26.9% (18/67). Radiologists commented on 25.5% (24/94) of the cervical ribs in 25.4% (27/67) of patients.

CONCLUSIONS

The prevalence of cervical ribs in the human population has been a source of uncertainty due to the degree of difficulty that comes in detecting this often subtle congenital variation. In our sample, the prevalence was 2.0% of patients. Our study determined that cervical ribs are underreported in patients undergoing cervical spine CT. Given the potential clinical implications of these anatomic variants, neuroradiologists must be more meticulous in identifying cervical ribs when reviewing cervical spine CT scans.

Cervical ribs are more prevalent in stillborn fetuses than in live-born infants and are strongly associated with fetal aneuploidy

This study was undertaken to determine the prevalence of cervical ribs in stillborn fetuses undergoing autopsy at our institution and to search for significant associations with cervical ribs. European studies have reported an increased prevalence of cervical ribs in patients with childhood cancer and in stillborn fetuses. We reviewed data from autopsies performed at Primary Children's Medical Center, Utah, between 2006 and 2009 on 225 stillborns (≥20 weeks) and 93 deceased live-born infants (<1 year). Digital fetal radiographs in anterior-posterior and lateral views had been taken of each subject. Chi-square analysis and general linear models were used for statistical analysis of the data. The overall prevalence of cervical ribs was higher in stillborns than in live-borns who died in the first year (43.1% vs 11.8%). Karyotypes were available for 93 (41.3%) of the stillborns. Of those, cervical ribs were present in 33 of 76 (43.4%) stillborns with normal karyotype and in 13 of 17 (76.4%) stillborns with aneuploidy. Females with unavailable karyotypes were more likely to have cervical ribs than those with normal karyotypes (P  =  0.0002). This greater likelihood was not observed in males. Among the stillborns with normal karyotypes, we found no statistically significant association with gender or gestational age at fetal death. There was also no statistically significant association between congenital anomalies and the presence of cervical ribs. Our findings support the hypothesis that cervical ribs are markers for disadvantageous developmental events occurring during blastogenesis and have been subject to strong negative selection during evolution.

Association of rib anomalies and childhood cancers

Background:

Congenital anomalies have been found more often in children with cancer than in those without. Rib abnormalities (RAs) have been associated with childhood cancer; however, studies have differed in the type of RAs and cancers implicated.

Methods:

Rib abnormalities were assessed predominantly by X-ray in a hospital-based case–control study.

Results:

There was a significant difference in the number of cases vs controls with RAs after controlling for age and sex, specifically for acute myelogenous leukaemia, renal tumours, and hepatoblastoma.

Conclusion:

The results of this study support previous reports that there is an association of rib anomalies with childhood cancer.

Analysis of cervical ribs in a series of human fetuses

In humans, an increasing body of evidence has linked the frequency of cervical ribs to stillbirths, other malformations and early childhood cancers. However, the frequency of cervical ribs in a putatively healthy fetal population is not sufficiently known to assess the actual medical risks of these prenatal findings. We therefore analyzed the presence of skeletal anomalies in a series of 199 electively aborted fetuses, which were whole-mount stained with alizarin red specific for skeletal tissues. Results show that approximately 40% of the fetuses had cervical ribs, even though external congenital abnormalities such as craniofacial and limb defects were absent. A literature overview indicates that the observed frequency of cervical ribs is comparable to results previously obtained for deceased fetuses with no or minor congenital anomalies, and higher than expected for healthy fetuses. This unexpected result can probably in part be explained by a higher detection rate of small cervical ribs when using alizarin red staining instead of radiographs. Additionally, studies in the literature suggest that the size of a cervical rib may indicate the severity of abnormalities, but this possibility requires further research. Anomalies of the axial skeleton are known to be caused by a disturbance of early development, which alters Hox gene expression, but in this study the origin of the stress could not be verified as maternal medical data were not available. The co-occurrence of rudimentary or absent 12th ribs in 23.6% of the cases with cervical ribs indicates that in approximately 8% of the fetuses a homeotic shift occurred over a larger part of the vertebral column. This suggests that the expression of multiple Hox genes may have been affected in these fetuses. Together, the high incidence of cervical ribs and also their co-occurrence with rudimentary or absent 12th ribs suggests that there may have been a disturbance of early development such that the studied fetuses are probably not informative about the general population. Future studies determining the frequency of cervical ribs in a more healthy fetal population are therefore needed to evaluate their potential as an indicator of medical risks.

Breaking evolutionary and pleiotropic constraints in mammals: On sloths, manatees and homeotic mutations

Background

Mammals as a rule have seven cervical vertebrae, except for sloths and manatees. Bateson proposed that the change in the number of cervical vertebrae in sloths is due to homeotic transformations. A recent hypothesis proposes that the number of cervical vertebrae in sloths is unchanged and that instead the derived pattern is due to abnormal primaxial/abaxial patterning.

Results

We test the detailed predictions derived from both hypotheses for the skeletal patterns in sloths and manatees for both hypotheses. We find strong support for Bateson's homeosis hypothesis. The observed vertebral and rib patterns cannot be explained by changes in primaxial/abaxial patterning. Vertebral patterns in sloths and manatees are similar to those in mice and humans with abnormal numbers of cervical vertebrae: incomplete and asymmetric homeotic transformations are common and associated with skeletal abnormalities. In sloths the homeotic vertebral shift involves a large part of the vertebral column. As such, similarity is greatest with mice mutant for genes upstream of Hox.

Conclusions

We found no skeletal abnormalities in specimens of sister taxa with a normal number of cervical vertebrae. However, we always found such abnormalities in conspecifics with an abnormal number, as in many of the investigated dugongs. These findings strongly support the hypothesis that the evolutionary constraints on changes of the number of cervical vertebrae in mammals is due to deleterious pleitropic effects. We hypothesize that in sloths and manatees low metabolic and activity rates severely reduce the usual stabilizing selection, allowing the breaking of the pleiotropic constraints. This probably also applies to dugongs, although to a lesser extent.

Infant leukemia and congenital abnormalities: a Children's Oncology Group study

BACKGROUND

Leukemia in infants is rare and has not been well studied apart from leukemia in older children. Differences in survival and the molecular characteristics of leukemia in infants versus older children suggest a distinct etiology, likely involving prenatal factors.

PROCEDURE

We examined the association between eight categories of maternally reported congenital abnormalities (CAs) (cleft lip or palate, spina bifida or other spinal defect, large or multiple birthmarks, other chromosomal abnormalities, small head or microcephaly, rib abnormalities, urogenital abnormalities, and other) and infant leukemia in a case-control study. The study included 443 cases diagnosed at <1 year of age at a Children's Oncology Group Institution in the United States or Canada from 1996 to 2006 and 324 controls. Controls were recruited from the cases' geographic area either by random digit dialing (1999-2002) or through birth certificates (2003-2008) and were frequency-matched to cases on birth year. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by unconditional logistic regression after adjustment for birth year and a measure of follow-up time to account for differences in the CA observation period.

RESULTS

No statistically significant associations were observed between infant leukemia and any CA (OR = 1.2; 95% CI: 0.8-1.9), birthmarks (OR = 1.4; 95% CI: 0.7-2.5), urogenital abnormalities (OR = 0.7; 95% CI: 0.2-2.0), or other CA (OR = 1.4; 95% CI: 0.7-2.8). Results were similar for acute lymphoblastic and myeloid leukemia cases. Fewer than five subjects were in the remaining CA categories precluding analysis.

CONCLUSIONS

Overall, we did not find evidence to support an association between CAs and infant leukemia.

The prevalence of cervical ribs in a London population

Cervical ribs are an important cause of neurovascular compression at the thoracic outlet. Previous studies have shown the prevalence of cervical ribs to be between 0.05 and 3%, depending on the sex and race of the population studied. We examined 1,352 chest radiographs to determine the prevalence of cervical ribs in a London population of mixed sex and ethnicity. Our study found that the overall prevalence of cervical ribs was 0.74% with a higher rate in females compared with males (1.09 and 0.42%, respectively). Of the 10 individuals with a cervical rib, five were on the left, three were on the right and two were bilateral. The presence of elongated C7 transverse processes (transverse apophysomegaly) was also noted. We found a total of 30 elongated transverse processes with an overall prevalence of 2.21%. They were also more common in females (3.43%) than males (1.13%).

Abnormal number of fetal ribs on 3-dimensional ultrasonography: associated anomalies and outcomes in 75 fetuses

OBJECTIVE

The purpose of this study was to describe the clinical importance of an abnormal number of fetal ribs.

METHODS

A retrospective study of all fetuses that were found to have an abnormal number of ribs during routine ultrasonographic examinations was performed. Volume data sets of the fetal ribs were acquired by either static 3- or 4-dimensional volume contrast imaging in plane C. In all cases, a meticulous survey of the fetal anatomy was performed, and prenatal and postnatal records were reviewed.

RESULTS

Seventy-five fetuses were found retrospectively to have an abnormal number of ribs. Ultrasonographic examinations were done between 14 and 31 weeks' gestation (mean, 21.8 weeks; median, 23 weeks). More than 24 ribs were found in 28 fetuses (37%), and fewer than 24 ribs were found in 47 (63%). Additional anomalies were found in 22 fetuses (29%). Cardiovascular anomalies were detected in 10 fetuses. Seven fetuses had renal anomalies. Two fetuses had mild ventriculomegaly, and 1 fetus had holoprosencephaly. Lung dysplasia was found in 2 cases. One fetus had enlarged nuchal translucency with wormian bones. Termination of pregnancy was performed in 3 cases because of major malformations. The other 19 fetuses with associated abnormalities and the 53 without associated anomalies were born alive with only minor anomalies.

CONCLUSIONS

An abnormal number of fetal ribs is an isolated finding in most cases. It may also be seen with major anomalies; however, more frequently the anomalies are minor, and the overall prognosis is good.

Cervical rib fracture: an unusual etiology of thoracic outlet syndrome in a child

Thoracic outlet syndrome in children is an extremely rare disorder. Only 5 previous reports were presented in the literature with a description of thoracic outlet syndrome in 8 children. In these cases, the diagnosis of a cervical rib was common. We describe a case of neurogenic thoracic outlet syndrome in a 9-year-old patient where the initial symptoms occurred 2 months after a fall. Clinically, the patient developed progressive pain, numbness and tingling along the inner surface of the left forearm and in the palmar surface of the fourth finger and lateral aspect of the fifth finger. A plain radiography showed a cervical rib fracture and an electrophysiologic study suggested the presence of left lower brachial plexus neuropathy. Her fractured cervical rib was resected through a supraclavicular approach. Her symptoms resolved completely in the postoperative period. Although very rare one should keep in mind the possibility of thoracic outlet syndrome in children, especially with a history of trauma over the shoulder girdle presenting with a cervical rib and a lower brachial plexopathy.

Syndromes and constitutional chromosomal abnormalities associated with Wilms tumour

Wilms tumour has been reported in association with over 50 different clinical conditions and several abnormal constitutional karyotypes. Conclusive evidence of an increased risk of Wilms tumour exists for only a minority of these conditions, including WT1 associated syndromes, familial Wilms tumour, and certain overgrowth conditions such as Beckwith-Wiedemann syndrome. In many reported conditions the rare co-occurrence of Wilms tumour is probably due to chance. However, for several conditions the available evidence cannot either confirm or exclude an increased risk, usually because of the rarity of the syndrome. In addition, emerging evidence suggests that an increased risk of Wilms tumour occurs only in a subset of individuals for some syndromes. The complex clinical and molecular heterogeneity of disorders associated with Wilms tumour, together with the apparent absence of functional links between most of the known predisposition genes, suggests that abrogation of a variety of pathways can promote Wilms tumorigenesis.