Thanatophoric dysplasia: case report of an autopsy complemented by postmortem computed tomographic study

Prenatal ultrasound findings and prenatal diagnosis of fetal skeletal dysplasia

OBJECTIVE

To analyze the value of prenatal ultrasound and molecular testing in diagnosing fetal skeletal dysplasia (SD).

METHODS

Clinical data, prenatal ultrasound data, and molecular results of pregnant women with fetal SD were collected in the ultrasound department of our clinic from May 2019 to December 2021.

RESULTS

A total of 40 pregnant women with fetal SD were included, with 82.5% exhibiting short limb deformity, followed by 25.0% with central nervous system malformations, 17.50% with facial malformations, 15% with cardiac malformations, and 12.5% with urinary system malformations. The genetic testing positive rate was 70.0% (28/40), with 92.8% (26/28) being single-gene disorders due to mutations in FGFR3, COL1A1, COL1A2, EVC2, FLNB, LBR, and TRPV4 genes. The most common SD subtypes were osteogenesis imperfecta (OI), thanatophoric dysplasia (TD), and achondroplasia (ACH). The gestational age (GA) at initial diagnosis for TD, OI, and ACH was 16.6, 20.9, and 28.3 weeks, respectively (p < 0.05), with no significant difference in femoral shortening between the three groups (p > 0.05). Of the OI cases, 5 out of 12 had a family history.

CONCLUSION

Short limb deformity is the most prevalent phenotype of SD. When fetal SD is suspected, detailed ultrasound screening should be conducted, combined with GA at initial diagnosis, family history, and molecular evidence, to facilitate more accurate diagnosis and enhance prenatal counseling and perinatal management.

Whole exome sequencing combined with dynamic ultrasound assessments for fetal skeletal dysplasias: 4 case reports

RATIONALE

Fetal skeletal anomalies are one of the most common and potentially pathogenic developmental abnormalities detected by ultrasound screening. Any suspected fetal skeletal dysplasias often require further comprehensive evaluations.

PATIENT CONCERNS

Here 4 families with adverse fetal skeletal system histories were enrolled, including their histories of gestation, childbirth, familial skeletal abnormalities, and pregnancy outcomes. The corresponding diagnosis were done by whole exome sequencing (WES) combined with dynamic examination.

DIAGNOSIS

All of the families were definitively diagnosed through cytogenetics, molecular genetics, ultrasound, combined with multidisciplinary evaluation. Both of the fetuses in case 1 and case 2 were diagnosed with thanatophoric dysplasia type I, while the neonate in case 3 was diagnosed with Apert syndrome and a 3-years-old proband daughter with Crouzon syndrome in case 4.

INTERVENTIONS

We conducted karyotyping, copy number variation sequencing (CNV-seq), combined with WES to evaluate genetic conditions of abnormal fetus, neonate or proband patient. WES was preferred to obtain a relatively definitive diagnosis.

OUTCOMES

In cases 1 and 2, the families decided to choose termination of pregnancy due to fatal dysplasias. The couple in case 3, delivered a female baby diagnosed with Apert syndrome. Fortunately, in case 4, the family, which had a 3-years-old baby with Crouzon syndrome, gave birth to a healthy baby through prenatal diagnosis.

LESSONS SUBSECTIONS

Invasive prenatal diagnosis and dynamic assessments for the management of fetal skeletal dysplasias could contribute to revealing possible causes of fetal skeletal abnormalities and help clinicians conduct further genetic counseling in clinical practice.

Diversity and Evolution of Mineralized Skeletal Tissues in Chondrichthyans

The diversity of skeletal tissues in extant vertebrates includes mineralized and unmineralized structures made of bone, cartilage, or tissues of intermediate nature. This variability, together with the diverse nature of skeletal tissues in fossil species question the origin of skeletonization in early vertebrates. In particular, the study of skeletal tissues in cartilaginous fishes is currently mostly restrained to tessellated cartilage, a derived form of mineralized cartilage that evolved at the origin of this group. In this work, we describe the architectural and histological diversity of neural arch mineralization in cartilaginous fishes. The observed variations in the architecture include tessellated cartilage, with or without more massive sites of mineralization, and continuously mineralized neural arches devoid of tesserae. The histology of these various architectures always includes globular mineralization that takes place in the cartilaginous matrix. In many instances, the mineralized structures also include a fibrous component that seems to emerge from the perichondrium and they may display intermediate features, ranging from partly cartilaginous to mostly fibrous matrix, similar to fibrocartilage. Among these perichondrial mineralized tissues is also found, in few species, a lamellar arrangement of the mineralized extracellular matrix. The evolution of the mineralized tissues in cartilaginous fishes is discussed in light of current knowledge of their phylogenetic relationships.

A Case of Osteogenesis Imperfecta Type II With Additional Balanced Translocation t(1;20)(p13;p11.2)

BACKGROUND

Osteogenesis imperfect (OI) type II is a genetic disorder of bone characterized by bone fragility, multiple fractures, severe bowing and shortening of long bones, and perinatal death due to respiratory insufficiency. It is mainly caused by mutations in the COL1A1 or COL1A2 genes, inherited in an autosomal dominant manner.

CASE REPORT

A fetal form of this disorder that included brachydactyly, macrocephaly, frontal bossing, soft calvarium, saddle nose, micrognathia, low set ears, and narrow thoracic cavity is described. A postmortem skeletal survey revealed multiple fractures, unossified skull, and long crumpled bones. The fetal karyotype revealed a balanced translocation t(1;20)(p13;p11.2). DNA sequencing detected a c.3065G > T transversion in exon 42 of the COL1A1 gene, a mutation associated with OI type II.

CONCLUSION

Although the balanced translocation t(1:20)(p13;p11.2) appears to be incidental in our case, identification of the specific mutation and translocation is important for estimation of genetic risk for another afflicted child.

A full-term infant with type II thanatophoric dysplasia

Objectives

To report a neonate with clinical findings consistent with thanatophoric dysplasia (TD). Only a few cases of this rare and lethal skeletal disorder have been reported in South-East Asia.

Case presentation

A 37-year-old Asian female, fourth gravida at 39 weeks, presented to our hospital for an elective cesarean section due to polyhydramnios, frank breech and gestational hypertension. The father was a 42-year-old Asian male. There was no history of rashes, fever, alcohol intake, substance drug abuse, smoking habit or radiation exposure. Ultrasound (US) of 34-weeks’ gestation found a baby with frontal bossing, prominent temporal lobe, clover-skull and low nasal bridge. The thoracic diameter was smaller than the abdominal diameter. Short limbs without bowing were noted in femur and humeral bones. The patient delivered a baby boy, 4115 g, APGAR scores were 5 and 7 at 1 and 5 min. The baby had a dysmorphic face, frontal bossing, low nasal bridge, low-set ears and short neck. The thorax was narrow and abdomen was protuberant. The upper and lower proximal limbs appeared short. A chest X-ray revealed short, curved ribs and opacification of both lungs. He had respiratory distress shortly after birth and had persistent severe respiratory distress despite adequate mechanical ventilation. On the third day, he had cardiac arrest; resuscitation was not done due to family request. The baby was declared deceased due to cardiopulmonary failure related to his congenital anomaly.

Conclusions

Ultrasonography could readily indicate TD prenatally. The pregnancy can continue up to late third trimester without miscarriage. Most of the neonates die in utero; those who survive are dependent on ventilator.