Abnormal gyration of the temporal lobe and megalencephaly are typical features of thanatophoric dysplasia and can be visualized prenatally by ultrasound

Should We Stop Calling Thanatophoric Dysplasia a Lethal Condition? A Case Report of a Long-Term Survivor

Thanatophoric dysplasia (TD) is a rare skeletal dysplasia commonly thought to be lethal. In this case report, we discuss a nine-year-old male with TD and review his parents' decision making shortly after their son was born, the technology needed to sustain him, and his parents' perception of his quality of life. We also summarize the clinical course of published long-term survivors with TD. Pediatric Palliative Care teams, especially those conducting perinatal palliative care consultations, are often asked to support families in the face of prognostic uncertainty. Our case report and review of the literature adds to the uncertainty of prognosis in TD and suggests that pediatric palliative care providers should be wary of the label “lethal.”

Fetal magnetic resonance imaging of skeletal dysplasias

BACKGROUND

Fetal magnetic resonance imaging (MRI) is obtained for prenatal diagnosis and prognostication of skeletal dysplasias; however, related literature is limited.

OBJECTIVE

The purpose of this study was to define the utility of fetal MRI for skeletal dysplasias and to report MRI findings associated with specific diagnoses.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board; informed consent was waived. Women referred for suspected fetal skeletal dysplasia who underwent MRI between January 2003 and December 2018 were included. Definitive diagnoses were determined by genetic testing, autopsy, physical examination and/or postnatal/postmortem imaging. Fetal MRI examinations and reports were reviewed. Descriptive statistics were used to summarize imaging findings.

RESULTS

Eighty-nine women were referred for fetal MRI for possible skeletal dysplasia. Forty-three (48%) were determined to have a diagnosis other than skeletal dysplasia and nine were excluded for lack of specific skeletal dysplasia diagnosis. Thirty-seven cases of skeletal dysplasia with available fetal MRI and specific diagnosis were included for analysis. Diagnoses included achondrogenesis (n=2), achondroplasia (n=5), Boomerang dysplasia (n=1), campomelic dysplasia (n=2), Jeune syndrome (n=1), Kniest dysplasia (n=1), osteogenesis imperfecta (n=15) and thanatophoric dysplasia (n=10). A specific skeletal dysplasia diagnosis was mentioned in 17/37 (46%) of MRI imaging reports and correct for 14/17 (82%). MRI findings were reported for each specific skeletal dysplasia diagnosis.

CONCLUSION

Fetal MRI is a useful diagnostic tool for skeletal dyplasias and excluded the diagnosis in nearly half of referred pregnancies. In addition to providing fetal lung volumes, fetal MRI demonstrates findings of the brain in achondroplasia and thanatophoric dysplasia, of the spine in achondroplasia and achondrogenesis, of the calvarium in osteogenesis imperfecta and thanatophoric dysplasia, and of the cartilage in Kniest dysplasia.

Prenatal diagnosis of hydrancephaly and enlarged cerebellum and cisterna magna in a fetus with thanatophoric dysplasia type II and a review of prenatal diagnosis of brain anomalies associated with thanatophoric dysplasia

OBJECTIVE

We present prenatal diagnosis of hydrancephaly and enlarged cerebellum and cisterna magna in a fetus with thanatophoric dysplasia type II (TD2) and a review of prenatal diagnosis of brain anomalies associated with TD.

CASE REPORT

A 33-year-old woman was referred for genetic counseling at 25 weeks of gestation because of fetal ultrasound abnormalities. Prenatal ultrasound at 14 weeks of gestation revealed an increased nuchal translucency (NT) and hydrocephalus. Level II ultrasound examination at 25 weeks of gestation revealed hydrancephaly, macrocephaly, a cloverleaf skull, frontal bossing, enlarged cerebellum and cisterna magna, a narrow chest, small ribs, short straight limbs. Amniocentesis revealed a karyotype of 46,XX. FGFR3 mutation analysis using the DNA extracted from uncultured amniocytes revealed a genotype of WT/c.1948A>G (p.Lys650Glu). The result was consistent with a K650E mutation in FGFR3 and TD2. The pregnancy was subsequently terminated.

CONCLUSION

Fetuses with TD2 may present increased NT, early onset hydrocephalus, enlarged cerebellum and cisterna magna, and hydrancephaly on prenatal ultrasound.

Temporal Lobe Malformations in Achondroplasia: Expanding the Brain Imaging Phenotype Associated with FGFR3-Related Skeletal Dysplasias

Thanatophoric dysplasia, achondroplasia, and hypochondroplasia belong to the fibroblast growth factor receptor 3 (FGFR3) group of genetic skeletal disorders. Temporal lobe abnormalities have been documented in thanatophoric dysplasia and hypochondroplasia, and in 1 case of achondroplasia. We retrospectively identified 13 children with achondroplasia who underwent MR imaging of the brain between 2002 and 2015. All children demonstrated a deep transverse temporal sulcus on MR imaging. Further common neuroimaging findings were incomplete hippocampal rotation (12 children), oversulcation of the mesial temporal lobe (11 children), loss of gray-white matter differentiation of the mesial temporal lobe (5 children), and a triangular shape of the temporal horn (6 children). These appearances are very similar to those described in hypochondroplasia, strengthening the association of temporal lobe malformations in FGFR3-associated skeletal dysplasias.

Temporal lobe dysplasia: a characteristic sonographic finding in thanatophoric dysplasia

OBJECTIVE

To determine the incidence of temporal lobe dysplasia (TLD) detected on prenatal ultrasound in thanatophoric dysplasia (TD) over an 11-year period in a tertiary referral center.

METHODS

An 11-year retrospective review of perinatal autopsies from 2002 to 2013 was performed to identify cases of TD. The ultrasound images and corresponding reports of all TD cases were examined for the presence of TLD. The same set of images subsequently underwent a retrospective review by a perinatal radiologist with knowledge of the features of TLD to determine whether they could be identified.

RESULTS

Thirty-one cases of TD underwent perinatal autopsy, and prenatal ultrasound imaging was available for review in 24 (77%). Mean gestational age at diagnosis of TD was 21.3 (range, 18-36) weeks. TLD was identified and reported in 6/24 (25%) cases; all six cases occurred after 2007. Retrospective interpretation of the ultrasound images identified features of TLD in 10 additional cases. In total, 16/24 (67%) cases displayed sonographic evidence of TLD. Temporal trends showed that TLD features were present in 50% (5/10) of all TD cases between 2002 and 2006 and in 79% (11/14) of those detected between 2007 and 2013.

CONCLUSIONS

At present, the detection rate of TLD by ultrasound is low but may be increased by modified brain images that enhance visualization of the temporal lobes. Prenatal identification of TLD may help in the prenatal diagnosis of TD and thus provide more accurate prenatal counseling and guide molecular investigations to confirm the specific diagnosis of TD.

Prenatal ultrasound and MRI findings of temporal and occipital lobe dysplasia in a twin with achondroplasia

Thanatophoric dysplasia, hypochondroplasia and achondroplasia are all caused by FGFR3 (fibroblast growth factor receptor 3) mutations. Neuropathological findings of temporal lobe dysplasia are found in thanatophoric dysplasia, and temporal and occipital lobe abnormalities have been described recently in brain imaging studies of children with hypochondroplasia. We describe twins discordant for achondroplasia, in one of whom the prenatal diagnosis was based on ultrasound and fetal MRI documentation of temporal and occipital lobe abnormalities characteristic of hypochondroplasia, in addition to the finding of short long bones. Despite the intracranial findings suggestive of hypochondroplasia, achondroplasia was confirmed following postnatal clinical and genetic testing. These intracranial abnormalities have not been previously described in a fetus with achondroplasia.

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.

Thanatophoric dysplasia: autopsy findings over a 25-year period

The aim of our study was to retrospectively assess morphological findings in thanatophoric dysplasia, particularly, in how many cases were cerebral manifestations with temporal lobe dysplasia identified. We also wanted to register and analyze the proportions between lung, brain, and body weight. Criteria for inclusion were an autopsy performed during the period ranging from 1985 to 2009 with a diagnosis of thanatophoric dysplasia. During a 25-year period 25 cases of thanatophoric dysplasia were registered. Temporal lobe dysplasia was recognized in 52% of the cases, and after 1998 temporal lobe dysplasia was described in all cases. In 19 cases the brain/body weight ratio was increased, and in all cases the lung/body weight ratio was below the corresponding ratio calculated according to standard measurements. In all but one case the ratio of brain to lung weight was increased. This study focuses on morphological findings, stressing the importance of temporal lobe dysplasia in confirming a diagnosis of thanatophoric dysplasia. Lung/body, brain/body, and brain/lung weight ratios confirm macrocephaly and lung hypoplasia, which are constant findings in cases involving thanatophoric dysplasia. Femur and brain morphology inclusive histology remains the ultimate tool for confirmation of this lethal condition, although it has to be seen in a context inclusive of radiological examination.