Premature cranial synostosis in X-linked hypophosphatemic rickets: possible precipitation by 1-alpha-OH-cholecalciferol intoxication

Characteristics of oral health of patients with X-linked hypophosphatemia: case reports and literature review

BACKGROUND

Oral health is impaired in X-linked hypophosphatemia (XLH), resulting in delayed dental development, malocclusion, and radiographic abnormalities. This study investigates the oral manifestations in Slovenian XLH patients, focusing on enamel and dentin abnormalities and a literature review of spontaneous periapical abscesses in XLH cases.

OBJECTIVES

To report XLH patients with specific oral signs and symptoms, histological analysis of affected teeth, and review of reported cases of XLH patients with spontaneous periapical abscesses.

METHODS

Case reports: Seven XLH patients from the National Registry of Patients with Rare Diseases underwent a detailed oral examination, including X-ray reviews. The patients who were expected to have tooth exfoliation or extraction were asked to donate their teeth for histological analysis by scanning electron microscopy.

LITERATURE SEARCH

A literature search of four electronic databases and a manual bibliography search aimed to identify documented cases of XLH with periapical abscesses up to January 21, 2024. Inclusion criteria were confirmed XLH patients with periapical abscesses in English peer-reviewed publications.

RESULTS

Tooth samples from three XLH patients showed reduced dentin mineralisation, affecting one-third to one-half of the outer dentin. Inadequate mineralisation, uneven dentin tubules, and cracks and chipping in the enamel were observed, indicating mineralisation deviations. Similar cracks extended into the dentin and were also present in the root of the examined tooth. Based on the content of the 75 items identified in the search, spontaneous abscesses are not uncommon in patients with XLH.

CONCLUSIONS

XLH significantly affects patients' lives and requires lifelong treatment. Dental examinations consistently revealed oral problems, including malocclusion. Histological analysis confirmed structural changes, especially in the dentin. Despite continued treatment, XLH patients may have an increased risk of oral pathologies. Further research is needed to understand the impact of XLH and its treatment on dental health.

Orthopedic and neurosurgical care of X-linked hypophosphatemia

X-linked hypophosphatemia (XLH) is due to mutations in the PHEX gene leading to unregulated production of FGF23 and uncontrollable hypophosphatemia. XLH is characterized in children by rickets, short stature, waddling gait, and leg bowing of variable morphology and severity. Phosphate supplements and oral vitamin D analogs partially or, in some cases, fully restore the limb straightness. XLH patients may also be affected by premature, complete, or partial ossification of sutures between cranial bone, which could eventually result in cranial dysmorphia, decreased intracranial volume, and secondary abnormally high intracranial pressure with a cerebral compression. Our goal is to address the criteria and the management of the skeletal complications associated with XLH, mainly orthopedic and neurosurgical care, and reflect on decision-making and follow-up complexities.

Clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia

X-linked hypophosphataemia (XLH) is the most common cause of inherited phosphate wasting and is associated with severe complications such as rickets, lower limb deformities, pain, poor mineralization of the teeth and disproportionate short stature in children as well as hyperparathyroidism, osteomalacia, enthesopathies, osteoarthritis and pseudofractures in adults. The characteristics and severity of XLH vary between patients. Because of its rarity, the diagnosis and specific treatment of XLH are frequently delayed, which has a detrimental effect on patient outcomes. In this Evidence-Based Guideline, we recommend that the diagnosis of XLH is based on signs of rickets and/or osteomalacia in association with hypophosphataemia and renal phosphate wasting in the absence of vitamin D or calcium deficiency. Whenever possible, the diagnosis should be confirmed by molecular genetic analysis or measurement of levels of fibroblast growth factor 23 (FGF23) before treatment. Owing to the multisystemic nature of the disease, patients should be seen regularly by multidisciplinary teams organized by a metabolic bone disease expert. In this article, we summarize the current evidence and provide recommendations on features of the disease, including new treatment modalities, to improve knowledge and provide guidance for diagnosis and multidisciplinary care.

High Incidence of Cranial Synostosis and Chiari I Malformation in Children With X-Linked Hypophosphatemic Rickets (XLHR)

X-linked hypophosphatemic rickets (XLHR) represents the most common form of genetic hypophosphatemia and causes rickets and osteomalacia in children because of increased FGF23 secretion and renal phosphate wasting. Even though cranial vault and craniovertebral anomalies of potential neurosurgical interest, namely early closure of the cranial sutures and Chiari type I malformation, have been observed in children with XLHR, their actual incidence and characteristics are not established. The aims of this study were to analyze the incidence of cranial and cervico-occipital junction (COJ) anomalies in children with XLHR and describe its features. This is a retrospective study of CT scans of the head and skull in 44 XLHR children followed at the French Reference Center for Rare Diseases of the Calcium and Phosphate Metabolism. Forty-four children with XLHR, 15 boys and 29 girls, aged 8.7 ± 3.9 years at time of CT scan, were studied. We found that 59% of XLHR children had a complete or partial fusion of the sagittal suture and 25% of XLHR children showed protrusion of the cerebellar tonsils. A history of dental abscesses was associated with craniosynostosis, and craniosynostosis was associated with abnormal descent of cerebellar tonsils. Only 2 patients showed neurologic symptoms. Four of 44 patients (9%) required neurosurgery. This study highlights that sagittal suture fusion and Chiari type I malformation are frequent complications of XLHR. The incidence of sagittal synostosis in XLHR is actually extremely high and was probably underestimated so far. Chiari type I malformation is also frequent. Because diagnosis of craniovertebral anomalies can be underestimated on a purely clinical basis, radiological studies should be considered in XLHR children if a proper diagnosis is warranted. © 2018 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals, Inc.

X-linked hypophosphatemic rickets and craniosynostosis

Bone mineralization is possible via complex interactions among fibroblast growth factor 23 (FGF23), phosphate-regulating gene with homologies to endopeptidases on the X-chromosome (PHEX), and matrix extracellular phosphoglycoprotein. A loss-of-function mutation in PHEX disrupts this interaction leading to hypophosphatemic rickets. X-linked hypophosphatemic (XLH) rickets is the most common form of metabolic rickets, and there have been reports linking XLH rickets to craniosynostosis. A clinical report of a patient with XLH rickets and craniosynostosis is presented with a review of literature. A review of physiology of bone mineralization reveals that, at high levels, there is cross-binding of FGF23 with FGF receptors 2 and 3 at the cranial sutures. This may be the reason for the common association of craniosynostosis and XLH rickets. There are complex interactions of proteins required for mineralization, proteins inhibiting mineralization, bone remodeling, and bone-renal phosphate homeostasis. Clarification of this pathway and reproducibility in a mouse model may pave the way for medical prevention of craniosynostosis in rickets.

Surgically assisted rapid palatal expansion: a literature review

Transverse maxillomandibular discrepancies are a major component of several malocclusions. Orthopedic and orthodontic forces are used routinely to correct a maxillary transverse deficiency (MTD) in a young patient. Correction of MTD in a skeletally mature patient is more challenging because of changes in the osseous articulations of the maxilla with the adjoining bones. Surgically assisted rapid palatal expansion (SARPE) has gradually gained popularity as a treatment option to correct MTD. It allows clinicians to achieve effective maxillary expansion in a skeletally mature patient. The use of SARPE to treat MTD decreases unwanted effects of orthopedic or orthodontic expansion. Our aim in this article is to present a comprehensive review of the literature, including indications, diagnosis, guidelines for case selection, a brief overview of the surgical techniques, orthodontic considerations, complications, risks, and limitations of SARPE to better aid the clinician in the management of MTD in skeletally mature patients.

Sagittal synostosis in X-linked hypophosphatemic rickets and related diseases

BACKGROUND

The recent observations of two new cases of X-linked hypophosphatemic rickets associated with premature closure of the sagittal suture prompted a review of similar cases seen in this institution.

OBJECTIVES

To review the clinical records and skull radiographs of 28 children with hypophosphatemic rickets in order to investigate the frequency and type of craniosynostosis and other cranial vault changes seen in these conditions and to review the literature for relevant findings.

MATERIALS AND METHODS

Clinical and imaging records were reviewed on 28 patients with hypophosphatemic rickets, all younger than 18 years. Most patients had X-linked hypophosphatemic rickets and a few had autosomal-dominant hypophosphatemic rickets or were non-familial cases.

RESULTS

Of the 28 patients, 13 had sagittal synostosis. Dolichocephaly was present in ten patients. The configuration of the cranial vault in some of these ten patients with dolichocephaly varied somewhat from that seen in nonsyndromic sagittal synostosis. In one patient, a Chiari I malformation was demonstrated by MRI. In another patient with increased intracranial pressure the sagittal suture closure was associated with lambdoidal synostosis. Dolichocephaly was not present in three patients, suggesting that the synostosis started later than in the other patients, probably in the second year of life, a period of slower brain growth than in the first year. The two patients in this group of three showed thickening and sclerosis of the cranial vault of uncertain etiology.

CONCLUSION

There is an increased risk of sagittal synostosis in hypophosphatemic rickets and related diseases in children. The appearance of the cranial vault in this type of synostosis can vary from that seen in nonsyndromic synostosis. In this setting, careful clinical and imaging follow-up is warranted.

The role of cranial expansion for craniocephalic disproportion

The appropriate treatment for craniocephalic disproportion, such as caused by slit ventricle syndrome, is uncertain. We have reviewed the treatment and outcomes of 4 children who underwent cranial expansion over a period of 5 years. The ages at cranial expansion were 16 months, 3 years 6 months and 2 at 6 years. Two children had slit ventricle syndrome and were treated with bilateral parietal expansions. Two children had non-syndromic craniosynostosis, one of these having vitamin D-resistant rickets. The latter 2 were treated with posterior cranial vault expansion, and one also had a craniocervical junction decompression performed. Post-operatively, symptoms of raised intracranial pressure resolved in all cases, and there was radiological evidence of re-establishment of normal CSF pathways. Although a rare condition, cranial expansion operations can be successful in appropriately selected cases of craniocephalic disproportion.

Craniosynostosis in X-linked hypophosphataemic rickets

A report of three cases of craniosynostosis in X-linked hypophosphataemic rickets (XLH) is presented. The literature is reviewed, suggesting that craniosynostosis is relatively common in XLH and that boys may be more at risk than girls. It is recommended that radiological screening be offered to all patients with XLH.

Premature craniosynostosis. A retrospective analysis of a series of 52 cases

A retrospective analysis of a consecutive series of 52 cases with premature craniosynostosis is presented. Excellent functional, cosmetic, and social results could be achieved by resection of prematurely fused sutures and the creation of artificial growth sutures. Pronounced skull deformities have been corrected using the "basket handle", the "visor plasty", and the "T- bone" techniques or a combination of several of these skull form correction techniques. The surgical correction of the skull base by the "frontal advancement" technique in combination with orbitotomy was only necessary in 2 of our cases and could have been considered in 2 additional cases viewed retrospectively. Our results support the hypothesis that the primary cause of skull deformity is the premature closure of vault sutures and not a primary deformity of the skull base.