Infantile osteopetrosis, craniosynostosis, and Chiari malformation type I with novel OSTEM1 mutation

Osteopetrosis with Arnold Chiari malformation type I

Osteopetrosis is a rare genetic disorder resulting in increased bone density and decreased bone remodelling. Bone expansion results in the crowding of neural foramina causing cranial nerve compression. Here, we describe a female infant in her mid infancy presented with no eye contact since birth, and abdominal distension for 2 months. On CT evaluation, sclerotic bones with bilateral optic canal narrowing were present. A crowded posterior fossa with Arnold Chiari type I malformation was seen on MRI evaluation, suggesting a rare association of osteopetrosis with Arnold Chiari's malformation.

Molecular Mechanisms of Craniofacial and Dental Abnormalities in Osteopetrosis

Osteopetrosis is a group of genetic bone disorders characterized by increased bone density and defective bone resorption. Osteopetrosis presents a series of clinical manifestations, including craniofacial deformities and dental problems. However, few previous reports have focused on the features of craniofacial and dental problems in osteopetrosis. In this review, we go through the clinical features, types, and related pathogenic genes of osteopetrosis. Then we summarize and describe the characteristics of craniofacial and dental abnormalities in osteopetrosis that have been published in PubMed from 1965 to the present. We found that all 13 types of osteopetrosis have craniomaxillofacial and dental phenotypes. The main pathogenic genes, such as chloride channel 7 gene (CLCN7), T cell immune regulator 1 (TCIRG1), osteopetrosis-associated transmembrane protein 1 (OSTM1), pleckstrin homology domain-containing protein family member 1 (PLEKHM1), and carbonic anhydrase II (CA2), and their molecular mechanisms involved in craniofacial and dental phenotypes, are discussed. We conclude that the telltale craniofacial and dental abnormalities are important for dentists and other clinicians in the diagnosis of osteopetrosis and other genetic bone diseases.

The clinical features of OSTM1-associated malignant infantile osteopetrosis: A retrospective, single-center experience over one decade

Mutation in OSTM1 give rise to the rarest and most lethal subtype of malignant infantile osteopetrosis (MIOP), and an improved understanding of OSTM1-associated MIOP would help with informed decision-making regarding symptom management and early palliative care referral. This retrospective study describes the clinical and laboratory features of patients with a genetic diagnosis of OSTM1 MIOP made between January 2011 and December 2021 in the Department of Pediatrics, Al-Adan Hospital, Kuwait. Twenty-two children had confirmed homozygous deletion in OSTM1 (13 females, nine males). Consanguinity was reported in almost all parents. 72.7% were diagnosed before the age of two months, most commonly incidentally with a high clinical suspicion. All 22 patients developed upper respiratory symptoms, hepatosplenomegaly, poor feeding, and had severe developmental delay. 80% of patients developed pain and/or irritability, and 40.9% were diagnosed with primary seizures. Bone fractures developed in 27% of patients, most likely iatrogenic, and some patients had hernia and gum abnormalities. The mean survival was 10.9 months. The clinical presentation, symptomatology, and mortality of our cohort were compared with other cases of OSTM1 MIOP identified through a comperhensive search of the PubMed database. The findings conclude that OSTM1 MIOP is a multi-systemic disease with distinct clinical features, of which neurological complications are the most severe and include nociplastic pain and irritability. Although orthopedic complications influence the trajectory of most patients with other forms of osteopetrosis, OSTM1 MIOP is driven by its neurological complications. Hence, OSTM1 should be regarded as a neurodegenerative disease with osteopetrosis as a comorbidity that warrants early palliative care referral.

Neonatal hydrocephalus: an atypical presentation of malignant infantile osteopetrosis

PURPOSE

Autosomal recessive osteopetrosis has a variable presentation, most commonly including failure to thrive, hypocalcemia, seizures, hepatosplenomegaly, hydrocephalus, vision or hearing loss, and cytopenias. Multiple symptoms are usually seen at presentation. The variability of presentation often delays diagnosis and subsequent treatment. Here, we present a case of an infant with this condition who initially presented with triventricular hydrocephalus with Chiari I malformation. This alone is not a common presentation of this disease, and we present this case to highlight autosomal recessive osteopetrosis as a potential diagnosis in infants presenting with hydrocephalus and discuss the other associated symptoms, management, and prognosis of this condition.

CASE REPORT

The patient was a full-term infant with a routine newborn period. At 6 months, the infant had macrocephaly and frontal bossing with a bulging fontanelle. She was found to have hydrocephalus with moderate ventriculomegaly involving the third and lateral ventricles with an associated Chiari 1 malformation. The infant was asymptomatic at the time. The infant was promptly referred to neurosurgery and underwent an uncomplicated ventriculoperitoneal shunt placement. Post-operative X-rays showed increased density of the skull with other bone changes suggestive of autosomal recessive osteopetrosis. Subsequent lab work and imaging studies were consistent with this condition. The diagnosis was confirmed by genetic testing, and the patient has undergone treatment with hematopoietic stem cell transplant.

CONCLUSION

Hydrocephalus is a common feature of this condition, typically seen in conjunction with other systemic symptoms and laboratory findings. Our patient had a limited initial presentation of triventricular hydrocephalus with Chiari I malformation and was otherwise clinically asymptomatic. There is limited literature of such a presentation, and we highlight this case to increase awareness, as timely diagnosis of these patients is critical for treatment and future outcomes.

Managing challenging pain and irritability in OSTM1 mutation-related infantile malignant osteopetrosis

Osteopetrosis describes a heterogeneous group of diseases characterised by increased bone density due to impaired osteoclast. The malignant infantile autosomal recessive (MIOP) form caused by mutations in OSTM1 is the most severe form of osteopetrosis. Children with this phenotype exhibit multisystemic complications, of which the neuropathic manifestations are the most severe. Infants with MIOP may present with pain and irritability that are likely to become continuous and debilitating as the disease progresses. There is limited understanding of the aetiology and management of pain in MIOP. Here, we describe a 2 month-old infant with OSTM1 mutation-related MIOP presenting with severe irritability and pain. This case provides the opportunity to discuss the cause and management of these distressing symptoms. We also review similar cases and the possible underlying mechanisms of pain and irritability to help provide a conceptual framework for the management of these symptoms in infants with OSTM1 MIOP.

Genetic Causes of Craniosynostosis: An Update

In 1993, Jabs et al. were the first to describe a genetic origin of craniosynostosis. Since this discovery, the genetic causes of the most common syndromes have been described. In 2015, a total of 57 human genes were reported for which there had been evidence that mutations were causally related to craniosynostosis. Facilitated by rapid technological developments, many others have been identified since then. Reviewing the literature, we characterize the most common craniosynostosis syndromes followed by a description of the novel causes that were identified between January 2015 and December 2017.

An Exceptional Neurosurgical Presentation of a Patient with Osteopetrosis

BACKGROUND

Osteopetrosis (OP) is a varied clinical condition caused by malfunction or insufficient development of osteoclasts, or both. Neurologic findings can occur because of osteopetrotic conditions restricting neural foramina through which the spinal cord, cranial nerves, or major vascular structures traverse the skull. Renal tubular acidosis (RTA) is a well-documented condition with OP. However, Chiari I malformation is rarely reported concomitantly with OP.

CASE DESCRIPTION

We present a patient with a known RTA who was admitted with a rapid progressive tetraparesis within 24 hours. Clinical and radiologic evaluation of the patient revealed OP with RTA together with Chiari I malformation and holocord hydromyelia. Management of the patient was started with correction of severe hypokalemia (K: 1.4 mEq/L), which resulted in dramatic improvement in tetraparesis. Two days later, a posterior fossa bone decompression with ventriculoperitoneal shunt placement during the same session led to prominent decrease in size of the ventricles and the hydromyelia on long-term follow-up.

CONCLUSIONS

Patients with OP can exhibit many clinical conditions. However, our case involved an unusual and rapid progressive tetraparesis, which could confuse the management as necessitating an emergent posterior fossa decompression. Stabilizing the metabolic status of the patient facilitated elective surgery, which further improved patient's neurologic findings and diminished hydromyelia on long-term follow-up.

Endoscopic third ventriculostomy for hydrocephalus in osteopetrosis: a case report and review of the literature

INTRODUCTION

There are very few reports in the literature associating in hydrocephalus in osteopetrosis. As a complication of shunt procedure, there are two reports on shunt malfunction due to osseous overgrowth at the burr hole in patients with osteopetrosis. We herein report a case of osteopetrosis with hydrocephalus that was successfully treated with endoscopic third ventriculostomy (ETV).

CASE REPORT

At 5 months of age, a male patient presented with developmental delay. Head computed tomography (CT) demonstrated triventricular hydrocephalus with a cerebellar tonsillar herniation. At 7 months of age, he underwent suboccipital decompression with decompression of the foramen magnum. The hydrocephalus did not improve postoperatively, and the patient was transferred to our hospital. At 12 months of age, the hydrocephalus was successfully treated with ETV. The postoperative period was uneventful. Postoperative CT demonstrated an improvement in the ventricle size.

CONCLUSIONS

The etiology of hydrocephalus in osteopetrosis is not completely understood; however, there have been several reports in which ETV was effective. ETV should be considered the treatment of choice for hydrocephalus in osteopetrosis, as it avoids the characteristic shunt complications that can occur in patients with osteopetrosis.

Case update on cranial osteopetrosis: which is the role of the neurosurgeon?

PURPOSE

Osteopetrosis (OP) is a rare skeletal disease, which can affect the skull base and calvaria. A multidisciplinary approach is mandatory and patient may need neurosurgical care. Few observations have been published, and optimal management of OP is not established yet.

METHOD

We report a case of an infant with OP diagnosed at 5 months, who presented signs of intracranial hypertension associated with unilateral blindness. Bone marrow allograft was performed at 6 months of age. At neurosurgical first examination at 11 months, the child was hypotonic, with severe amblyopia; features of bicoronal synostosis were appreciated, with tense anterior fontanel bulging indicating synostotic oxycephaly. Head circumference had decreased from +3 SD to +1SD. Cerebral CT scan showed reduction of intracranial volume, inward thickening of the calvaria, bilateral stenosis of optic canal, ventricular dilatation, enlarged arachnoid spaces, and tonsillar herniation. We performed cranial vault expansion with frontal advancement and bi parietal decompression, thinning of the inner table, unroofing of the left orbit and optic canal in order to obtain optic nerve decompression.

RESULTS

Postoperative course was uneventful, and the patient was discharged on day 8. Vision was unchanged but rapid improvement of axial tonus was noted. The CT scan showed satisfactory calvarial expansion with regression of tonsillar herniation.

CONCLUSIONS

Neurosurgical evaluation and care are necessary in the context of a multidisciplinary approach to the patient affected by osteopetrosis. Cranial vault remodeling and expansion should be considered in patients with sign of intracranial hypertension. Timing of optic canal decompression is to be defined.

Mutation Screening of Candidate Genes in Patients with Nonsyndromic Sagittal Craniosynostosis

BACKGROUND

Craniosynostosis is a condition that includes the premature fusion of one or multiple cranial sutures. Among various craniosynostosis forms, sagittal nonsyndromic craniosynostosis is the most prevalent. Although different gene mutations have been identified in some craniosynostosis syndromes, the cause of sagittal nonsyndromic craniosynostosis remains largely unknown.

METHODS

To screen for candidate genes for sagittal nonsyndromic craniosynostosis, the authors sequenced DNA of 93 sagittal nonsyndromic craniosynostosis patients from a population-based study conducted in Iowa and New York states. FGFR1-3 mutational hotspots and the entire TWIST1, RAB23, and BMP2 coding regions were screened because of their known roles in human nonsyndromic or syndromic sagittal craniosynostosis, expression patterns, and/or animal model studies.

RESULTS

The authors identified two rare variants in their cohort. A FGFR1 insertion c.730_731insG, which led to a premature stop codon, was predicted to abolish the entire immunoglobulin-like III domain, including the ligand-binding region. A c.439C>G variant was observed in TWIST1 at its highly conserved loop domain in another patient. The patient's mother harbored the same variant and was reported with jaw abnormalities. These two variants were not detected in 116 alleles from unaffected controls or seen in the several databases; however, TWIST1 variant was found in a low frequency of 0.000831 percent in Exome Aggregation Consortium database.

CONCLUSIONS

The low mutation detection rate indicates that these genes account for only a small proportion of sagittal nonsyndromic craniosynostosis patients. The authors' results add to the perception that sagittal nonsyndromic craniosynostosis is a complex developmental defect with considerable genetic heterogeneity.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, II.

Upward Translation of Cerebellar Tonsils following Surgical Expansion of Supratentorial Cranial Vault: A Unified Biomechanical Explanation of Chiari Type I

Cerebellar tonsils moved significantly upward in 3 patients with Chiari type I who underwent supratentorial cranial vault expansion to alleviate intracranial pressure related to multisutural craniosynostosis. The Chiari type I deformities in these patients were the biomechanical consequence of posterior fossa-cerebellar disproportion caused by supratentorial craniocerebral disproportion secondary to multisutural craniosynostosis. The authors postulate that all cases of Chiari type I deformity share the sine qua non feature of posterior fossa-cerebellar disproportion.

A unifying theory for the multifactorial origin of cerebellar tonsillar herniation and hydrocephalus in osteopetrosis

OBJECT

Osteopetrosis is a rare congenital metabolic bone disease. There are very few reports in the literature associating cerebellar tonsillar herniation (CTH) and hydrocephalus requiring neurosurgical attention. The authors present cases of osteopetrosis requiring neurosurgical intervention from their practice and offer a detailed account of the literature.

METHODS

A retrospective review was conducted at the authors' institution, and all children with osteopetrosis requiring neurosurgical attention were identified. Medical charts and radiographic studies were reviewed. Data including age at presentation, sex, symptoms at presentation, age at follow-up, the presence of any neurological comorbidities, and surgical procedures performed were recorded.

RESULTS

Four patients were identified as having osteopetrosis requiring neurosurgical attention at the authors' institution between January 1, 2005, and January 1, 2014. There were 3 females and 1 male with an average age at presentation of 11.1 years; patients were observed for a mean of 4.4 years. All of the patients were identified as harboring jugular foraminal stenosis and CTH. Seventy-five percent of these patients developed hydrocephalus, and in those cases a triventricular pattern of dilation was noted. One patient developed syringomyelia. Three of the 4 patients underwent neurosurgical procedures. Cerebrospinal fluid diversion was performed in 2 patients via a ventriculoperitoneal shunt in one case and an endoscopic third ventriculostomy (ETV) in the other. The former patient required a proximal revision at 2 years for bony overgrowth at the site of the bur hole. Two patients underwent a suboccipital decompression. In patients undergoing CSF diversion, there was improvement in ventricle size.

CONCLUSIONS

Variable degrees of hindbrain crowding and/or CTH are mentioned throughout the literature, suggesting that this entity is nearly always present in this patient population. The progressive triventricular hydrocephalus seen in these cases results from a complex combination of both communicating and noncommunicating pathology, which may depend on the type of osteopetrosis, age at presentation, and the presence and degree of venous collateralization, and it appears that the hydrocephalus is more prevalent and more likely to be treated in infants and in the younger, school-aged population. The acquired hindbrain fullness in conjunction with the triventricular pattern of hydrocephalus has kept the authors enthusiastic regarding the use of ETV in these complicated cases.

Closing the Gap: Genetic and Genomic Continuum from Syndromic to Nonsyndromic Craniosynostoses

Craniosynostosis, a condition that includes the premature fusion of one or multiple cranial sutures, is a relatively common birth defect in humans and the second most common craniofacial anomaly after orofacial clefts. There is a significant clinical variation among different sutural synostoses as well as significant variation within any given single-suture synostosis. Craniosynostosis can be isolated (i.e., nonsyndromic) or occurs as part of a genetic syndrome (e.g., Crouzon, Pfeiffer, Apert, Muenke, and Saethre-Chotzen syndromes). Approximately 85 % of all cases of craniosynostosis are nonsyndromic. Several recent genomic discoveries are elucidating the genetic basis for nonsyndromic cases and implicate the newly identified genes in signaling pathways previously found in syndromic craniosynostosis. Published epidemiologic and phenotypic studies clearly demonstrate that nonsyndromic craniosynostosis is a complex and heterogeneous condition supporting a strong genetic component accompanied by environmental factors that contribute to the pathogenetic network of this birth defect. Large population, rather than single-clinic or hospital-based studies is required with phenotypically homogeneous subsets of patients to further understand the complex genetic, maternal, environmental, and stochastic factors contributing to nonsyndromic craniosynostosis. Learning about these variables is a key in formulating the basis of multidisciplinary and lifelong care for patients with these conditions.