Short stature, mental retardation, craniosynostosis, Klippel-Feil syndrome, Scheuerman kyphosis, rib gaps and other distinctive skeletal and genital anomalies. A new syndrome?

Genetic insights into the 'sandwich fusion' subtype of Klippel-Feil syndrome: novel FGFR2 mutations identified by 21 cases of whole-exome sequencing

BACKGROUND

Klippel-Feil syndrome (KFS) is a rare congenital disorder characterized by the fusion of two or more cervical vertebrae during early prenatal development. This fusion results from a failure of segmentation during the first trimester. Although six genes have previously been associated with KFS, they account for only a small proportion of cases. Among the distinct subtypes of KFS, "sandwich fusion" involving concurrent fusion of C0-1 and C2-3 vertebrae is particularly noteworthy due to its heightened risk for atlantoaxial dislocation. In this study, we aimed to investigate novel candidate mutations in patients with "sandwich fusion."

METHODS

We collected and analyzed clinical data from 21 patients diagnosed with "sandwich fusion." Whole-exome sequencing (WES) was performed, followed by rigorous bioinformatics analyses. Our focus was on the six known KFS-related genes (GDF3, GDF6, MEOX1, PAX1, RIPPLY2, and MYO18). Suspicious mutations were subsequently validated through in vitro experiments.

RESULTS

Our investigation revealed two novel exonic mutations in the FGFR2 gene, which had not previously been associated with KFS. Notably, the c.1750A > G variant in Exon 13 of FGFR2 was situated within the tyrosine kinase domain of the protein, in close proximity to several established post-translational modification sites. In vitro experiments demonstrated that this certain mutation significantly impacted the function of FGFR2. Furthermore, we identified four heterozygous candidate variants in two genes (PAX1 and MYO18B) in two patients, with three of these variants predicted to have potential clinical significance directly linked to KFS.

CONCLUSIONS

This study encompassed the largest cohort of patients with the unique "sandwich fusion" subtype of KFS and employed WES to explore candidate mutations associated with this condition. Our findings unveiled novel variants in PAX1, MYO18B, and FGFR2 as potential risk mutations specific to this subtype of KFS.

De novo inv(2)(p12q34) associated with Klippel-Feil anomaly and hypodontia

The present case report describes a patient with Klippel-Feil anomaly (KFA) and oligodontia, carrying a de novo pericentric inversion of chromosome 2 (p12q34). KFA is characterised by congenital vertebral fusion of the cervical spine and a wide spectrum of associated anomalies. It therefore constitutes a heterogenous group of clinical conditions and has been classified morphologically, although its aetiology remains unclear. We present an 18-year-old female with KFA, associated with congenital impairment of hearing, psychomotor retardation, speech limitation, short stature, spinal scoliosis, facial asymmetry and latent hypothyroidism. No renal anomaly or heart disease was present. In addition, she exhibited oligodontia of both the deciduous and permanent dentition, a unique characteristic that has not yet been reported in any non-cleft palate KFA case.

CONCLUSION

The current report of a patient with oligodontia and an inversion on chromosome 2 may aid in the identification of novel genes for oligodontia.

Double vagina with sex reversal, congenital diaphragmatic hernia, pulmonary and cardiac malformations--another case of Meacham syndrome

We report a female infant of 42 weeks gestation with a left sided diaphragmatic hernia and a hypoplastic left heart. A true double vagina, absent uterus and abnormal male gonads were found in the presence of normal external female genitalia. Conventional G band karyotyping of skin samples revealed a normal male karyotype. The aetiology and inheritance are unknown. We believe this to be the fifth reported case of a recognizable syndrome first reported by Meacham [(1991). Am J Med Genet 41:478-481].