Diagnosis of thanatophoric dysplasia using clinical exome screening.

Bone dysplasias are a broad, heterogeneous group of diseases. Thanatophoric dysplasia is a rare bone dysplasia, but it is the most common lethal skeletal dysplasias. The major role in diagnostics plays a high-quality ultrasound examination in the 2nd trimester and the latest methods of genetic testing, including clinical exome testing. Knowing the correct diagnosis is crucial for the future of the fetus and the couple.

De novo variants of dominant monogenic disorders in Vietnam detected by a noninvasive prenatal test: a case series.

Background: Noninvasive prenatal tests for monogenic diseases (NIPT-SGG) have recently been reported as helpful in early-stage antenatal screening. Our study describes the clinical and genetic features of cases identified by NIPT-SGG. Materials & methods: In a cohort pregnancy with abnormal sonograms, affected cases were confirmed by invasive diagnostic tests concurrently, with NIPT-SGG targeting 25 common dominant single-gene diseases. Results: A total of 13 single-gene fetuses were confirmed, including Noonan and Costello syndromes, thanatophoric dysplasia, achondroplasia, osteogenesis imperfecta and Apert syndrome. Two novel variants seen were tuberous sclerosis complex (TSC2 c.4154G>A) and Alagille syndrome (JAG1 c.3452del). Conclusion: NIPT-SGG and standard tests agree on the results for 13 fetuses with monogenic disorders. This panel method of screening can benefit high-risk Vietnamese pregnancies, but further research is encouraged to expand on the causative gene panel.

Orthopaedic Manifestations of Thanatophoric Dwarfism: A Case Report.

CASE: We report the rare case of a 3-year-old male patient with thanatophoric dwarfism, a fatal skeletal dysplasia that arises from an autosomal dominant mutation in the fibroblast growth factor receptor 3 gene. The role of the orthopaedic surgeon in the in the management of this disease is discussed. CONCLUSION: We advocate for the close monitoring of disease progression by the orthopaedic surgery team and offer a potential surgical intervention that may help prevent cardiorespiratory demise.

Skeletal dysplasias of the fetus and infant: comprehensive review and our experience over a 10-year period.

We present a comprehensive review dealing with rare genetic skeletal disorders. More than 400 entities are included in the latest classification. The most severe or lethal phenotypes are identifiable in the prenatal period and the pregnancy can be terminated. Perinatal autopsy and posmortem X-rays are crucial in providing a definitive diagnosis. The number of cases confirmed by genetic testing is increasing. We report our own experience with genetic skeletal disorders based on 41 illustrative fetal and neonatal cases which we encountered over a 10-year period. Thanatophoric dysplasia and osteogenesis imperfecta represent approximately half of the cases coming to autopsy. Achondrogenesis type 2 and hypochondrogenesis, short-rib dysplasia, chondrodysplasia punctata, campomelic dysplasia and achondroplasia are less common. Skeletal dysplasias with autosomal recessive inheritance are the least frequent, e.g. perinatally lethal hypophophatasia, achondrogenesis type 1A, diastrophic dysplasia/atelosteogenesis type 2 or mucolipidosis type 2 (I cell disease).

Genetic examination for fetuses with increased nuchal translucency by exome sequencing.

AIM: This retrospective study aimed to investigate the value of exome sequencing (ES) in fetuses with isolated first-trimester increased nuchal translucency (NT) and normal chromosomes. METHODS: ES was performed on 103 fetuses with isolated first trimester increased NT and normal chromosomes. The detection rate of monogenic conditions was analyzed. RESULTS: Diagnostic variants were detected in nine cases in which phenotypes and genotypes correlated well, two positive cases were Thanatophoric dysplasia type I, and one case was Kabuki syndrome, which had been detected in previous studies. Eight of the nine cases with diagnostic variants developed additional structural malformations later in pregnancy. Among the nine positive cases, six had a NT thickness between 95th percentile (95th-3.4 mm), and three cases with an increased NT of 3.5 mm or greater. Also, there was no statistical difference in the diagnosis of diagnostic variants in cases with or without a thickened nuchal fold (NF). CONCLUSIONS: The diagnostic yield of prenatal ES is low for fetuses with an isolated increased NT. In addition to Noonan syndrome, there are additional genetic syndromes such as Kabuki syndrome and Thanatophoric dysplasia type I that are potentially associated with an increased NT. A cut-off of greater than the 95th percentile may be useful in case selection for ES. Whether it is clinically meaningful to monitor NF values for fetuses with isolated increased NT and normal chromosomes worth considering.

Fetal autopsy for the diagnosis of skeletal dysplasia and comparison with prenatal ultrasound findings over a 16-year period.

OBJECTIVES: To evaluate the relationship between prenatal ultrasonography (USG) and fetal autopsy findings. METHODS: Among 453 pregnancy terminations performed because of fetal anomalies on prenatal USG, 54 with skeletal dysplasia on fetal autopsy were included in this retrospective study. RESULTS: The most common diagnoses among the 54 fetal autopsies were osteogenesis imperfecta (n=12), dysostosis (n=10), achondroplasia (n=9), arthrogryposis (n=6), and thanatophoric dysplasia (n=6). The prenatal USG and fetal autopsy findings showed complete agreement in 35 cases (64.8%), partial agreement in nine cases (16.6%), and disagreement in 10 cases (18.5%). CONCLUSIONS: Fetal autopsy via perinatal pathology is essential for precise identification of the type of skeletal dysplasia; it should be routinely performed to confirm the diagnosis of prenatally detected fetal anomalies. Autopsy is vital for accurate prenatal diagnosis and the 'gold standard' technique for the identification of clinically important abnormalities.

Collagen X Marker Levels are Decreased in Individuals with Achondroplasia.

Collagen X marker (CXM) is a degradation fragment of collagen type X. It is a real-time biomarker of height velocity with established norms. Plasma C-type natriuretic peptide (CNP) and NTproCNP levels have also been found to correlate with growth velocity in the general population and are elevated in individuals with achondroplasia compared with age- and sex-matched controls. Collagen X marker levels in people with fibroblast growth factor receptor 3 (FGFR3)-opathies have never been systematically measured. The objective of this study was to measure CXM in a population of dwarfism caused by FGFR3-opathies. Using the same cohort in which CNP and NTproCNP levels were previously measured, archived serum aliquots from 63 children with achondroplasia, six with hypochondroplasia, and two with thanatophoric dysplasia had CXM concentrations measured. Results were plotted against age- and sex-specific norms, and standard deviation scores were plotted for comparison between clinical diagnoses. CXM levels were significantly decreased (p < 0.0001) in children with achondroplasia compared with age- and sex-matched controls. Temporal patterns of change in CXM levels were sex-dependent. As the FGFR3 pathway was more constitutively active, CXM levels decreased. New tools are emerging to study impact of skeletal dysplasia on growth plate regulation and function.

Fetal Skeletal Dysplasias: Radiologic-Pathologic Classification of 72 Cases.

ObjectiveThe aim of this study was to classify the fetal skeletal dysplasias (FSD) in a series of affected fetuses based on radio-pathologic criteria. Materials and methods: We gathered clinicopathologic data of 72 cases which were diagnosed among 5995 autopsies performed over a 8-year period. Results: The prevalence of FSD was 1.2:100 autopsies. The overall sex ratio (M:F) was 1.25. Gestational age was between 17 and 24 weeks in 60% of cases. The FSD were classified into 13 distinct pathologic groups. Four major groups were identified: (1) Osteogenesis imperfecta (21 cases, 29%); (2) FGFR3 chondrodysplasia (18 cases, 25%); (3) Ciliopathies (9 cases, 12%); and (4) Sulfation disorders (7 cases, 10%). Thanatophoric dysplasia type 1 and lethal osteogenesis imperfecta were the most common skeletal dysplasias. Conclusion: Our study demonstrates the usefulness of the radio-pathologic examination in the diagnosis and accurate classification of the FSD, thus enabling better targeting of genetic counseling.

Development of individuals with thanatophoric dysplasia surviving beyond infancy.

BACKGROUND: This study aimed to analyze the physical and psychosocial development of long-term survivors (age >1 year) of thanatophoric dysplasia (TD). METHODS: The participants were 20 long-term survivors recruited from a cohort obtained through a nationwide survey for TD conducted across 147 pediatric departments in Japan between 2012 and 2016. Their guardians consented to participate in this study. Medical and psychosocial information was collected through questionnaires and interviews with primary physicians and guardians. RESULTS: The participants were 1.2-27.8 years old, and all showed marked growth deficiency. The mean length at birth was 36 cm (-3.4 SD to -7.9 SD). The adult height (age >16 years) was <-15.2 SD. All individuals showed severely delayed psychomotor development. The highest level of psychosocial development was equivalent to that at 2 years of age. Skin disorders (acanthosis nigricans and seborrheic keratoses) were common. Eleven subjects had been hospitalized or institutionalized consistently after birth, and nine had been moved to home care, and four were exclusively orally fed. All individuals required assisted ventilation. CONCLUSIONS: Long-term survival of TD individuals is common. Some individuals enjoy home-based lives; however, they are severely psychosocially and physically disabled and require meticulous respiratory and nutritional support.

Thanatophoric dysplasia type 1 with temporal lobe dysplasia: Report of a case along with differential diagnosis.

Thanatophoric dysplasia type 1 (TD1) is a lethal form of osteochondral dysplasia due to mutation of FGFR3 gene. In addition to severe shortening of the limbs there is temporo-occipital lobe dysplasia along with a range of other CNS anomalies. In this report we describe the radiological and anatomical features at autopsy in neonate with TD1 along with the CNS anomalies. We have also summarized the key distinguishing features of TD1 from other common types of osteochondral dysplasia. An accurate diagnosis is important for genetic counseling and impact on future pregnancies.

Lethal and life-limiting skeletal dysplasias: Selected prenatal issues.

Skeletal dysplasias are a heterogeneous group of congenital bone and cartilage disorders with a genetic etiology. The current classification of skeletal dysplasias distinguishes 461 diseases in 42 groups. The incidence of all skeletal dysplasias is more than 1 in every 5000 newborns. The type of dysplasia and associated abnormalities affect the lethality, survival and long-term prognosis of skeletal dysplasias. It is crucial to distinguish skeletal dysplasias and correctly diagnose the disease to establish the prognosis and achieve better management. It is possible to use prenatal ultrasonography to observe predictors of lethality, such as a bell-shaped thorax, short ribs, severe femoral shortening, and decreased lung volume. Individual lethal or life-limiting dysplasias may have more or less specific features on prenatal ultrasound. The prenatal features of the most common skeletal dysplasias, such as thanatophoric dysplasia, osteogenesis imperfecta type II, achondrogenesis, and campomelic dysplasia, are discussed in this article. Less frequent dysplasias, such as asphyxiating thoracic dystrophy, fibrochondrogenesis, atelosteogenesis, and homozygous achondroplasia, are also discussed.

Early prenatal presentation of the cartilage-hair hypoplasia / anauxetic dysplasia spectrum of disorders mimicking recurrent thanatophoric dysplasia.

Three sibling fetuses identified with limb shortening and thoracic narrowing at twelve weeks' gestation on first trimester ultrasound examination are presented. The parents were non-consanguineous, Caucasian, healthy, of normal stature and had a healthy normal daughter. The radiographic abnormalities were highly suggestive of thanatophoric dysplasia, but molecular analysis failed to identify a pathogenic variant in FGFR3. The three fetuses were found to have identical compound heterozygous mutations in RMRP in trans, one inherited from the mother and one from the father. This represents the early prenatal presentation and fetal findings of metaphyseal dysplasia type McKusick (Cartilage-hair hypoplasia; CHH)/anauxetic dysplasia spectrum of disorders.

Achondroplasia-First Report from India of a Rare FGFR3 Gene Variant.

The clinical manifestations of FGFR3 sequence variations can vary from mild unnoticed short stature to neonatal lethal dwarfism and can be causative of phenotypes including achondroplasia, hypochondroplasia, and thanatophoric dysplasia. Clinical data describe an 11 month old girl with restricted growth and preserved intellect. She had rhizomelic short stature with peculiar facies but no Acanthosis nigricans. In view of the absence of the hotspot mutation c.1138 G>A/G>C (p.Gly380Arg), complete gene sequencing was done that revealed a rare sequence variation, NM_000142.4:c.1043C>G (p.Ser348Cys) in FGFR3. This sequence variation has not been reported from India so far. This report emphasizes the benefit of sequencing the whole gene in individuals who are negative for hotspot mutation of achondroplasia with strong clinical suspicion.

Thanatophoric Skeletal Dysplasia: A Case Report.

Thanatophoric skeletal dysplasiais the most lethal, rare, sporadic birth defect due to de novo mutation in the fibroblast growth factor receptor-3. Clinically this is characterized by shortening of the limbs (micromelia), small conical thorax, flat vertebral bodies and macrocephaly at birth. We encountered a similar case with ultrasonographic findings suggestive of Thanatophoric Skeletal Dysplasia which resulted in the death of the baby within an hour of birth. Almost all cases of this condition have been reported to have died interuterinally or a few days after birth.

Rapid prenatal diagnosis of skeletal dysplasia using medical trio exome sequencing: Benefit for prenatal counseling and pregnancy management.

OBJECTIVE: The aim of this study is to explore the utility of rapid medical trio exome sequencing (ES) for prenatal diagnosis using the skeletal dysplasia as an exemplar. METHOD: Pregnant women who were referred for genetic testing because of ultrasound detection of fetal abnormalities suggestive of a skeletal dysplasia were identified prospectively. Fetal samples (amniocytes or cord blood), along with parental blood, were send for rapid copy number variations testing and medical trio ES in parallel. RESULTS: Definitive molecular diagnosis was made in 24/27 (88.9%) cases. Chromosomal abnormality (partial trisomy 18) was detected in one case. Sequencing results had explained the prenatal phenotype enabling definitive diagnoses to be made in 23 cases. There were 16 de novo dominant pathogenic variants, four dominant pathogenic variants inherited maternally or paternally, two recessive conditions with pathogenic variants inherited from unaffected parents, and one X-linked condition. The turnaround time from receipt of samples in the laboratory to reporting sequencing results was within 2 weeks. CONCLUSION: Medical trio ES can yield very timely and high diagnostic rates in fetuses presenting with suspected skeletal dysplasia. These definite diagnoses aided parental counseling and decision making in most of cases.

Thanatophoric dysplasia: a case report.

A case of thanatophoric dysplasia with sudden death at term is hereby presented. Thanatophoric dysplasia is an uncommon, lethal skeletal dysplasia which is associated with mutation in the extracellular region of fibroblast growth factor receptor 3 (FGFR3). It is an autosommal dominant condition that has sporadic occurrence and early ultrasound scan has not been of great benefit in its detection. Diagnosis is mostly made in the third trimester. The fetal death is usually due to severe respiratory insufficiency from a reduced thoracic capacity and hypoplastic lungs and/or respiratory failure due to brainstem compression. In view of the autosomal dominance of TD, it will be advisable for a woman with previous history to have prenatal screening to relieve parental anxiety and prevent late detection.

Clinical features and molecular genetic analysis of thanatophoric dysplasia type I in a neonate with a de novo c.2419 T > C (p. Ter807Arg) (X807R) mutation in FGFR3.

We present a case report that entails prenatal ultrasonography, postnatal characteristics, and molecular genetic analysis of a newborn who presented with thanatophoric dysplasia type I (TDI) with a mutation in the fibroblast growth factor receptor 3 gene (FGFR3). A malformed newborn with tachypnea, delivered by caesarean at the gestational age of 39 weeks, was the first child of nonconsanguineous parents by a spontaneous pregnancy. Features in prenatal ultrasonography and postnatal radiography were consistent with the diagnosis of TDI, presenting with short body length (38 cm, <3rd percentile), redundant skin folds, a narrow thorax with a bust of 29.5 cm (3-5th percentile), and macrocephaly with a head circumference of 36 cm (>97th percentile). The proposita had postnatal dyspnea and unfortunately died of respiratory failure at the age of 13 days. Molecular genetic analysis revealed a mutation of c.2419 T > C (p. Ter807Arg) (X807R) in FGFR3. Live-born infants with TDI are exceedingly rare, and we hereby report a newborn with a c.2419 T > C mutation in FGFR3, emphasizing phenotype with clinical characteristics and ultrasonographic and X-ray findings, to raise awareness about the heterogeneous patterns of TD.

National survey of prevalence and prognosis of thanatophoric dysplasia in Japan.

BACKGROUND: Thanatophoric dysplasia (TD) is a rare congenital disease of the skeletal system, with an incidence of 1.68-8.3 per 100 000 births, but statistical data on the estimated number of TD patients across Japan are not available. The aim of this study was therefore to investigate the prevalence and prognosis of TD in Japan. METHODS: A nationwide primary questionnaire survey was conducted. RESULTS: A total of 127 obstetric, 186 pediatric, and 115 orthopedic facilities provided responses. Excluding duplications, we identified 73 patients with TD. Of the 73 cases, 15 were abortions, four were stillbirths, 51 were live births, and three had unknown details. Of the 51 live newborns, 27 died ≤7 days after birth, with an early neonatal mortality rate of 56%. Of the 24 newborns who survived the early neonatal period, 16 survived for ≥1 year. All of the 24 newborns received respiratory management and survived during the early neonatal period. Of the 51 live newborns, 25 did not receive respiratory management and died ≤2 days after birth. CONCLUSIONS: The prevalence of TD in Japan is estimated to be at 1.1 (95%CI: 0.84-1.37) per 100 000 births, but the actual incidence is expected to be higher. To our knowledge, we have confirmed for the first time that newborns with TD may not always die during the early neonatal period but can survive the early neonatal period with appropriate respiratory management. Therefore, the term "thanatophoric dysplasia" does not accurately reflect the nature of the disease.