Craniosynostosis in pycnodysostosis: broadening the spectrum of the cranial flat bone abnormalities
Débora Bertola1, Cassio Amaral, Chong Kim
1Unidade de Genética, Instituto da Criança, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil. debora.bertola@icr.usp.br
Insights
Pycnodysostosis, a skeletal disorder, typically shows delayed cranial suture closure. However, this study found premature fusion of the coronal suture in all evaluated patients, suggesting a complex role for cathepsin K.
Area of Science:
- Genetics
- Orthopedics
- Developmental Biology
Background:
- Pycnodysostosis is a rare autosomal recessive skeletal dysplasia.
- It results from deficient cathepsin K, crucial for bone matrix degradation and remodeling.
- Characteristic features include osteosclerosis, bone fragility, short stature, and delayed cranial suture closure.
Purpose of the Study:
- To investigate the occurrence of craniosynostosis in patients with pycnodysostosis.
- To evaluate the potential contradictory cranial suture findings in this condition.
Main Methods:
- Retrospective review of six unrelated patients diagnosed with pycnodysostosis.
- Clinical assessment for typical pycnodysostosis features and specific evaluation of cranial suture status.
Main Results:
- All six patients presented with premature fusion of the coronal suture, a feature contrasting with typical delayed suture closure.
- No signs of cranial hypertension were observed in the patients.
- One patient had undergone surgical correction for craniosynostosis.
Conclusions:
- Pycnodysostosis can exhibit paradoxical cranial suture findings: both delayed closure and premature fusion (craniosynostosis).
- The precise role of cathepsin K in cranial suture patency requires further investigation.
- The clinical significance of craniosynostosis in pycnodysostosis remains to be determined.
Abstract:
Pycnodysostosis is a rare autosomal recessive skeletal dysplasia caused by the absence of active cathepsin K, which is a lysosomal cysteine protease that plays a role in degrading the organic matrix of bones, acting in bone resorption and bone remodeling. The disease is primarily characterized by osteosclerosis, bone fragility, short stature, acro-osteolysis, and delayed closure of the cranial sutures. A differing feature, cranial synostosis, has occasionally been described in this disorder. We reviewed six unrelated patients with pycnodysostosis (mean age of 10 years and 4 months) in order to evaluate the presence of craniosynostosis. In addition to the typical findings of the condition, they all presented premature fusion of the coronal suture. Although none of them showed signs of cranial hypertension, one patient had had the craniosynostosis surgically corrected previously. These data suggest that the cranial sutures in pycnodysostosis can display contradictory features: wide cranial sutures, which are commonly described, and craniosynostosis. The clinical impact of this latter finding still remains to be elucidated. Further studies are necessary to address more precisely the role of cathepsin K in suture patency.
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