FGFR2 mutation in a Chinese family with unusual Crouzon syndrome

Infigratinib, a selective FGFR1-3 tyrosine kinase inhibitor, alters dentoalveolar development at high doses

BACKGROUND

Fibroblast growth factor receptor-3 (FGFR3) gain-of-function mutations are linked to achondroplasia. Infigratinib, a FGFR1-3 tyrosine kinase inhibitor, improves skeletal growth in an achondroplasia mouse model. FGFs and their receptors have critical roles in developing teeth, yet effects of infigratinib on tooth development have not been assessed. Dentoalveolar and craniofacial phenotype of Wistar rats dosed with low (0.1 mg/kg) and high (1.0 mg/kg) dose infigratinib were evaluated using micro-computed tomography, histology, and immunohistochemistry.

RESULTS

Mandibular third molars were reduced in size and exhibited aberrant crown and root morphology in 100% of female rats and 80% of male rats at high doses. FGFR3 and FGF18 immunolocalization and extracellular matrix protein expression were unaffected, but cathepsin K (CTSK) was altered by infigratinib. Cranial vault bones exhibited alterations in dimension, volume, and density that were more pronounced in females. In both sexes, interfrontal sutures were significantly more patent with high dose vs vehicle.

CONCLUSIONS

High dose infigratinib administered to rats during early stages affects dental and craniofacial development. Changes in CTSK from infigratinib in female rats suggest FGFR roles in bone homeostasis. While dental and craniofacial disruptions are not expected at therapeutic doses, our findings confirm the importance of dental monitoring in clinical studies.

Crouzon syndrome in a fraternal twin: A case report and review of the literature

BACKGROUND

Crouzon syndrome (CS; OMIM 123500) is an autosomal dominant inherited craniofacial disorder caused by mutations in the fibroblast growth factor receptor 2 (FGFR2) gene. CS is characterized by craniofacial dysostosis, exophthalmos, and facial anomalies with hypoplastic maxilla and relative mandibular prognathism.

CASE SUMMARY

Our report involves a 6-year-old fraternal twin boy with many caries in the oral cavity who presented with characteristic features of CS based on clinical and radiographic examinations along with Sanger sequencing. The fraternal girl did not show any abnormalities indicating CS. Carious teeth and poor oral hygiene were managed promptly through administering appropriate behavior guidance, orthodontic treatment was planned, and preventive procedures were described.

CONCLUSION

CS could occur in a fraternal twin caused by a de novo mutation of the FGFR2 gene. Oral hygiene instruction, preventive programs on oral hygiene, orthodontic treatment, and maxillary osteotomy were required for treatment.

Inherited FGFR2 mutation in a Chinese patient with Crouzon syndrome and luxation of bulbus oculi provoked by trauma: a case report

Background

Crouzon syndrome (CS), which results from fibroblast growth factor receptor 2 mutations, is associated with craniosynostosis, exophthalmos, and other symptoms. Herein, we report the genetic abnormalities detected in a Chinese family with autosomal dominant CS, combined with luxation of the eyeball. This luxation was a consequence of the trauma to the shallow orbits.

Case presentation

The proband was a 4-year-old boy. He accidentally fell, following which luxation of the bulbus oculi occurred immediately. Computed tomography and magnetic resonance imaging clearly revealed ocular proptosis. Upon physical examination, the proband, his father, and grandfather had ocular proptosis, shallow orbits, and mid-face hypoplasia. However, their hands and feet were clinically normal. Genomic DNA was extracted from the peripheral blood through a polymerase chain reaction performed for the target sequence. Genetic assessments revealed a heterozygous missense mutation (c.1012G > C, p.G338R) in exon 10 of the human FGFR2, cosegregated with the disease phenotype in this family. These findings confirmed the diagnosis of CS.

Discussion

CS is usually caused by FGFR2 mutations. While there are a few reports of luxation of the bulbus oculi in Chinese families with CS, the ocular proptosis, shallow orbits, combined with luxation of eyeball after trauma observed in this patient were particularly interesting. Our findings enhance the current knowledge of traumatic luxation concomitant with CS.

Evolutionary conserved networks of human height identify multiple Mendelian causes of short stature

Height is a heritable and highly heterogeneous trait. Short stature affects 3% of the population and in most cases is genetic in origin. After excluding known causes, 67% of affected individuals remain without diagnosis. To identify novel candidate genes for short stature, we performed exome sequencing in 254 unrelated families with short stature of unknown cause and identified variants in 63 candidate genes in 92 (36%) independent families. Based on systematic characterization of variants and functional analysis including expression in chondrocytes, we classified 13 genes as strong candidates. Whereas variants in at least two families were detected for all 13 candidates, two genes had variants in 6 (UBR4) and 8 (LAMA5) families, respectively. To facilitate their characterization, we established a clustered network of 1025 known growth and short stature genes, which yielded 29 significantly enriched clusters, including skeletal system development, appendage development, metabolic processes, and ciliopathy. Eleven of the candidate genes mapped to 21 of these clusters, including CPZ, EDEM3, FBRS, IFT81, KCND1, PLXNA3, RASA3, SLC7A8, UBR4, USP45, and ZFHX3. Fifty additional growth-related candidates we identified await confirmation in other affected families. Our study identifies Mendelian forms of growth retardation as an important component of idiopathic short stature.

Detection of G338R FGFR2 mutation in a Vietnamese patient with Crouzon syndrome

Crouzon syndrome is a rare autosomal dominant genetic disorder, which causes the premature fusion of the cranial suture. Fibroblast growth factor receptor 2 (FGFR2) mutations are well-known causatives of Crouzon syndrome. The current study aimed to assess the FGFR2 gene associated with Crouzon syndrome in a Vietnamese family of three generations and to characterize their associated clinical features. The family included in the present study underwent complete clinical examination. A patient was clinically examined and presented with typical features of Crouzon syndrome including craniosynostosis, shallow orbits, ocular proptosis and midface hypoplasia. However the patient had normal hands and feet, a normal hearing ability and normal intelligence. Genomic DNA collected from all family members (except from a 16 week-old-foetus) and 200 unrelated control subjects from the same population was extracted from leukocytes obtained from peripheral blood samples. Genomic DNA was extracted from the 16-week-old foetus via the amniotic fluid of the mother. All coding sequences of FGFR2 were amplified via polymerase chain reaction and directly sequenced. A heterozygous FGFR2 missense mutation (c.1012G>C, p.G338R) in exon 10 was identified in the patient with Crouzon but not in other family members, the 16 week-old-foetus or the controls. This mutation was therefore determined to be the causative agent of Crouzon syndrome. In addition, a novel heterozygous silent mutation (c.1164C>T, p.I388I) in exon 11 of the FGFR2 gene was identified in the patient with Crouzon, his mother and the 16-week-old fetus, but not in other family members. The mutation in exon 10 of FGRF2 was confirmed via restriction-enzyme digestion. The gain of the BsoBI site confirmed the FGFR2 mutation in exon 10 of the patient with Crouzon. This molecular finding may provide useful information to aid clinicians in the diagnosis of Crouzon syndrome and may also aid early prenatal diagnoses.