Abnormal timing in the prenatal ossification of vertebral column and hand in Crouzon syndrome

Extremely severe scoliosis, heterotopic ossification, and osteoarthritis in a three-generation family with Crouzon syndrome carrying a mutant c.799T>C FGFR2

Background

Crouzon syndrome is a rare and complex autosomal dominant craniosynostosis syndrome with a prevalence of approximately 1 in 60,000 births. The typical features are craniosynostosis, proptosis, midfacial hypoplasia, and noncranial manifestations, including deformities in the cervical spine, elbow, and fingers. Crouzon syndrome is usually caused by pathogenic variants in the fibroblast growth factor receptor 2 (FGFR2) gene.

Methods

We reported a three‐generation family with Crouzon syndrome; the proband showed extremely severe limb abnormalities. The clinical features were obtained by physical examination and radiographic examination. Sanger sequencing of all 18 exons of FGFR2 was conducted to identify the disease‐causing mutation.

Results

The proband was a 44‐year‐old man who showed characteristics of Crouzon syndrome, including craniofacial dysostosis, shallow orbits, proptosis, midface hypoplasia, beaked nose, strabismus, short superior lip, short stature, and neck injection. In addition to these typical characteristics, radiographic examination showed severe scoliosis, heterotopic ossification of the elbows, knee osteoarthritis, metacarpophalangeal joint valgus, collapse of the articular surface of the thumb metacarpal, knuckle ossification and fusion. Sanger sequencing identified a heterozygous pathogenic variant c.799T>C, p.(Ser267Pro) in exon 7 of FGFR2 in affected individuals.

Conclusion

Crouzon syndrome in this three‐generation family was caused by c.799T>C FGFR2, and the patient showed a different phenotypic appearance from other Crouzon patients with c.799T>C FGFR2.

Surgical Correction of Severe Kyphoscoliosis Associated with Crouzon Syndrome with Serious Postoperative Respiratory Problems: A Case Report

CASE

A 12-year-old girl with Crouzon syndrome presented to our hospital with scoliosis (114°) and kyphosis from T8 to T12 (138°). After she had been in halo-gravity traction for 2 weeks, we performed posterior correction and fusion surgery from T3 to L3, with a posterior vertebral column resection of T10. She experienced postoperative respiratory failure and remained on a ventilator for 4 weeks. With rehabilitation, the respiratory function had recovered by postoperative week 8. At the 2-year follow-up, there was no loss of correction or any other complication.

CONCLUSION

Serious perioperative respiratory complications may occur when a patient with Crouzon syndrome is treated surgically.

Breaking evolutionary and pleiotropic constraints in mammals: On sloths, manatees and homeotic mutations

Background

Mammals as a rule have seven cervical vertebrae, except for sloths and manatees. Bateson proposed that the change in the number of cervical vertebrae in sloths is due to homeotic transformations. A recent hypothesis proposes that the number of cervical vertebrae in sloths is unchanged and that instead the derived pattern is due to abnormal primaxial/abaxial patterning.

Results

We test the detailed predictions derived from both hypotheses for the skeletal patterns in sloths and manatees for both hypotheses. We find strong support for Bateson's homeosis hypothesis. The observed vertebral and rib patterns cannot be explained by changes in primaxial/abaxial patterning. Vertebral patterns in sloths and manatees are similar to those in mice and humans with abnormal numbers of cervical vertebrae: incomplete and asymmetric homeotic transformations are common and associated with skeletal abnormalities. In sloths the homeotic vertebral shift involves a large part of the vertebral column. As such, similarity is greatest with mice mutant for genes upstream of Hox.

Conclusions

We found no skeletal abnormalities in specimens of sister taxa with a normal number of cervical vertebrae. However, we always found such abnormalities in conspecifics with an abnormal number, as in many of the investigated dugongs. These findings strongly support the hypothesis that the evolutionary constraints on changes of the number of cervical vertebrae in mammals is due to deleterious pleitropic effects. We hypothesize that in sloths and manatees low metabolic and activity rates severely reduce the usual stabilizing selection, allowing the breaking of the pleiotropic constraints. This probably also applies to dugongs, although to a lesser extent.

Chiari malformation and odontoid panus causing craniovertebral stenosis in a child with Crouzon's syndrome

Crouzon's disease is a well-known disorder affecting multiple organ systems, specifically a craniofacial disorder with highly variable penetrance and severity of deformity. Crouzon's patients typically have anomalies of the skull base leading to gross distortion of the cranium and in some cases the cervicocranium. We present a 5-year-old girl with Crouzon's disease who suffered from an acquired Chiari I malformation after insertion of a ventriculoperitoneal shunt and a coexistent ventral odontoid panus. Both these lesions were causing cervicomedullary compression. The literature is controversial on the surgical management of anterior and posterior compression at the craniocervical junction. We review the literature on surgical options for decompression at the craniocervical junction and offer our surgical case as a treatment option for patients in this rare clinical situation.