Diagnosis of skeletal dysplasia by multidisciplinary assessment: a report of two cases of thanatophoric dysplasia

Skeletal Dysplasias That Cause Thoracic Insufficiency in Neonates: Illustrative Case Reports

Skeletal dysplasias are a heterogeneous group of conditions associated with various abnormalities of the skeleton. Some of them are perinatally lethal and can be diagnosed at birth. Lethality is usually due to thoracic underdevelopment and lung hypoplasia. A correct diagnosis and typing of the skeletal disorder is essential for the prognosis as is genetic counseling of the family. A retrospective review of 12 cases of clinico-radiologic diagnosis of skeletal dysplasia, leading to thoracic insufficiency, was conducted.We aimed to make differential diagnosis with special emphasis on radiological findings, and to emphasize the importance of parental counseling.

Thanatophoric dysplasia. Correlation among bone X-ray morphometry, histopathology, and gene analysis

OBJECTIVE

Documentation through X-ray morphometry and histology of the steady phenotype expressed by FGFR3 gene mutation and interpolation of mechanical factors on spine and long bones dysmorphism.

MATERIALS AND METHODS

Long bones and spine of eight thanatophoric dysplasia and three age-matched controls without skeletal dysplasia were studied after pregnancy termination between the 18th and the 22nd week with X-ray morphometry, histology, and molecular analysis. Statistical analysis with comparison between TD cases and controls and intraobserver/interobserver variation were applied to X-ray morphometric data.

RESULTS

Generalized shortening of long bones was observed in TD. A variable distribution of axial deformities was correlated with chondrocyte proliferation inhibition, defective seriate cell columns organization, and final formation of the primary metaphyseal trabeculae. The periosteal longitudinal growth was not equally inhibited, so that decoupling with the cartilage growth pattern produced the typical lateral spurs around the metaphyseal growth plates. In spine, platyspondyly was due to a reduced height of the vertebral body anterior ossification center, while its enlargement in the transversal plane was not restricted. The peculiar radiographic and histopathological features of TD bones support the hypothesis of interpolation of mechanical factors with FGFR3 gene mutations.

CONCLUSIONS

The correlated observations of X-ray morphometry, histopathology, and gene analysis prompted the following diagnostic workup for TD: (1) prenatal sonography suspicion of skeletal dysplasia; (2) post-mortem X-ray morphometry for provisional diagnosis; (3) confirmation by genetic tests (hot-spot exons 7, 10, 15, and 19 analysis with 80-90% sensibility); (4) in negative cases if histopathology confirms TD diagnosis, research of rare mutations through sequential analysis of FGFR3 gene.

Filho RL, Rosa RFM, Maia CR, Graziadio C, Paskulin GA. Diagnóstico pré-natal de displasia tanatofórica: papel do ultrassom fetal

OBJETIVO: Relatar o caso de um paciente com displasia tanatofórica, uma forma autossômica dominante e letal de nanismo, diagnosticado ainda no período pré-natal, e revisar a literatura, discutindo os principais diagnósticos diferenciais e ressaltando a importância do ultrassom fetal na identificação de fetos portadores dessa displasia. DESCRIÇÃO DO CASO: O paciente é o segundo filho de pais jovens sem história familiar de doenças genéticas. O ultrassom fetal realizado com 35 semanas de gestação mostrou polidrâmnio, proeminência frontal e desproporção entre crânio e tronco, com hipoplasia torácica e encurtamento dos ossos longos, compatível com o diagnóstico de displasia tanatofórica. Ao nascimento, a criança era pequena e possuía hipotonia, macrocefalia, fontanelas amplas, hipoplasia de face média, olhos protrusos, hemangioma plano no nariz e pálpebras, nariz em sela, micrognatia, pescoço e tórax curtos e encurtamento importante de braços, antebraços, coxas e pernas. A avaliação radiográfica mostrou crânio com grande diâmetro transverso, tórax com costelas curtas e corpos vertebrais reduzidos, importante encurtamento e deformidade dos ossos longos dos membros superiores e inferiores (os fêmures eram curvos) e hipoplasia da bacia. Esses achados confirmaram o diagnóstico pré-natal de displasia tanatofórica. O paciente evoluiu para o óbito poucos dias após o nascimento devido à insuficiência respiratória. COMENTÁRIOS: A ultrassonografia fetal é um método não invasivo capaz de diagnosticar inúmeras displasias ósseas, incluindo a tanatofórica. A importância do diagnóstico intra-útero reside no fato de que auxilia no diagnóstico diferencial, e permite o aconselhamento genético à família.

Prenatal diagnosis of skeletal dysplasias: contribution of three-dimensional computed tomography

OBJECTIVE

To describe the contribution of 3-dimensional computed tomography (3D-CT) in the prenatal diagnosis of skeletal dysplasias (SD) in a cohort of patients with inconclusive diagnosis by ultrasound (US).

METHODS

Between May 2007 and February 2010, six pregnant women with suspected fetal SD on US examination but with no specific diagnosis were studied with 3D-CT. The images were evaluated by a multidisciplinary team who proposed a likely diagnosis. Further postnatal workup included clinical and radiological evaluation in all cases. Prenatal and postnatal diagnoses were compared.

RESULTS

The use of 3D-CT provided a precise diagnosis confirmed postnatally in 5/6 patients. These included osteogenesis imperfecta type II (n = 2), osteogenesis imperfecta type III (n = 1), chondrodysplasia punctata (n = 1) and thanatophoric dysplasia type I (n = 1). A precise diagnosis could not be made in 1 case - either pre- or postnatally.

CONCLUSION

Prenatal 3D-CT contributed to the diagnosis of the specific fetal SD in the majority of these cases. 3D-CT may have a complementary role to US where fetal SD is suspected, but no specific diagnosis can be made using US alone. Further studies on clinical performance and risk-benefit analysis are needed.

A guide to the recognition of skeletal disorders in the fetus

The discovery of fetal skeletal abnormality on prenatal US mandates an extended study of the fetus. This extended examination includes specific views and measurements of the fetal skeleton. Lethality can be predicted if severe pulmonary hypoplasia is present. Specific diagnosis of a fetal osteochondrodysplasia is difficult; a collaborative approach among obstetric, neonatal and genetic services is necessary to provide the parents with all available information regarding the pregnancy. Pediatric radiologists who have experience in radiologic assessment of osteochondrodystrophies of infants and children can provide expertise in this area.

Prenatal diagnosis of fetal skeletal dysplasias by combining two-dimensional and three-dimensional ultrasound and intrauterine three-dimensional helical computer tomography

OBJECTIVE

To evaluate the contribution of new imaging techniques in the prenatal diagnosis of skeletal dysplasia.

METHODS

Between May and October 2003, a prospective study was conducted in a single referral center. Three-dimensional ultrasound (3D-US) and three-dimensional helical computer tomography (3D-HCT) were performed after two-dimensional ultrasound (2D-US) in six cases of skeletal dysplasia. Diagnostic accuracy and detailed findings with each of the three techniques were compared with postnatal radiological findings.

RESULTS

There were three cases of achondroplasia, two cases of osteogenesis imperfecta type II and one case of chondrodysplasia punctata. Termination of pregnancy was performed in five cases and one fetus with osteogenesis imperfecta type II was delivered at term by Cesarean section. 2D-US made the correct diagnosis in four cases. 3D-US and 3D-HCT achieved an accurate diagnosis in all six cases. 3D-HCT and 3D-US identified significantly more abnormalities than did 2D-US (3D-HCT: 94.3% (33/35); 3D-US: 77.1% (27/35); 2D-US: 51.4% (18/35); P < 0.01). The diagnosis was made between 27 and 36 weeks' gestation in all cases. The advantage of 3D-HCT over 3D-US was the possibility of imaging the entire fetus.

CONCLUSION

3D-US and 3D-HCT seem to be useful complementary methods to 2D-US, and may improve accuracy of the prenatal diagnosis of skeletal disorders. These new imaging technologies may have a role in the prenatal multidisciplinary approach to the diagnosis of skeletal dysplasias.

Nuchal Translucency and Ductus venosus Blood Flow as Early Sonographic Markers of Thanatophoric Dysplasia

Thanatophoric dysplasia (TD) is the most frequent form of lethal osteochondrodysplasias. Prenatal diagnosis is commonly accomplished in the second-trimester scan, but occasionally TD may not be clearly distinguished from the other osteochondrodysplasias, with consequent important prognostic implications. However, in order to confirm the diagnosis, complementary radiological, pathological and molecular studies are mandatory. We present a case of TD diagnosed in the late first trimester with the contribution of nuchal translucency combined with ductus venosus blood flow assessment.

Congenital abnormalities of the musculoskeletal system: Perinatal evaluation and long-term outcome

Many musculoskeletal malformations can be detected by prenatal US. Whether isolated or part of a syndrome, these anomalies can have a significant impact on the entire life of the individual. Nonfatal conditions may be subtle and become more recognizable in the second and third trimester. After delivery, radiography helps confirm the diagnosis. US, CT, and MRI all have a role in imaging the primary abnormality, the follow-up effects of treatment, and in monitoring for potential complications that may develop over time. Three-dimensional imaging has an increasing role, in US, CT, and MRI, both in the prenatal and postnatal periods.