Mucopolysaccharidosis type I and craniosynostosis

Craniosynostosis: current conceptions and misconceptions

Cranial bones articulate in areas called sutures that must remain patent until skull growth is complete. Craniosynostosis is the condition that results from premature closure of one or more of the cranial vault sutures, generating facial deformities and more importantly, skull growth restrictions with the ability to severely affect brain growth. Typically, craniosynostosis can be expressed as an isolated event, or as part of syndromic phenotypes. Multiple signaling mechanisms interact during developmental stages to ensure proper and timely suture fusion. Clinical outcome is often a product of craniosynostosis subtypes, number of affected sutures and timing of premature suture fusion. The present work aimed to review the different aspects involved in the establishment of craniosynostosis, providing a close view of the cellular, molecular and genetic background of these malformations.

Craniosynostosis and metabolic bone disorder. A review

INTRODUCTION

Some metabolic bone disorders may result in the premature closure of one or more calvarial sutures during childhood, potentially leading to a cranioencephalic disproportion. The aim of this paper is to review the characteristics and consequences of craniosynostosis associated with metabolic disorder.

MATERIAL AND METHODS

A review of the literature on metabolic forms of craniosynostosis was performed.

RESULTS

The most common forms of craniosynostosis associated with metabolic bone disorder were isolated sagittal suture fusion with or without scaphocephaly, and sagittal suture fusion associated with coronal suture fusion (oxycephaly) or also with lambdoid suture fusion (pansynostosis). Synostosis may be well-tolerated, but in some subjects results in neurodevelopmental and functional impairment that is sometimes severe.

CONCLUSION

The impact of metabolic synostosis is very variable, depending on the specific underlying metabolic disease, with a large spectrum of morphological and functional consequences. Diagnosis should be early and management should be carried out by a multidisciplinary team with expertise in both rare skeletal disorders and craniosynostosis. The impact of emergent medical therapies recently developed for some of these diseases will be assessed by systematic coherent follow-up of international registries.

Craniosynostosis affects the majority of mucopolysaccharidosis patients and can contribute to increased intracranial pressure

BACKGROUND

The mucopolysaccharidoses are multisystem lysosomal storage diseases characterized by extensive skeletal deformities, including skull abnormalities. The objective of this study was to determine the incidence of craniosynostosis in the different mucopolysaccharidosis (MPS) types and its clinical consequences.

METHODS

In a prospective cohort study spanning 10 years, skull imaging and clinical evaluations were performed in 47 MPS patients (type I, II, VI, and VII). A total of 215 radiographs of the skull were analyzed. The presence and type of craniosynostosis, the sutures involved, progression over time, skull shape, head circumference, fundoscopy, and ventriculoperitoneal shunt (VPS) placement data were evaluated.

RESULTS

Craniosynostosis of at least one suture was present in 77% of all 47 MPS patients (≤ 6 years of age in 40% of all patients). In 32% of all MPS patients, premature closure of all sutures was seen (≤ 6 years of age in 13% of all patients). All patients with early closure had a more severe MPS phenotype, both in the neuronopathic (MPS I, II) and non-neuronopathic (MPS VI) patient groups. Because of symptomatic increased intracranial pressure (ICP), a VPS was placed in six patients, with craniosynostosis as a likely or certain causative factor for the increased pressure in four patients. One patient underwent cranial vault expansion because of severe craniosynostosis.

CONCLUSIONS

Craniosynostosis occurs in the majority of MPS patients. Since the clinical consequences can be severe and surgical intervention is possible, skull growth and signs and symptoms of increased ICP should be monitored in both neuronopathic and non-neuronopathic patients with MPS.

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.

Markedly Elevated Intracranial Pressure Treated With Cranial Vault Expansion, Instead of CSF Shunting, in a Child With Hurler-Scheie Syndrome and Multiple Suture Craniosynostosis

Despite a known association of mucopolysaccharidoses (MPS) and craniosynostosis, treatment of elevated intracranial pressure (ICP) in these patients is primarily cerebrospinal fluid (CSF) shunting. We present a unique case of Hurler-Scheie syndrome with multisuture craniosynostosis and elevated ICP, without ventriculomegaly, where elevated ICP was successfully treated with extensive cranial vault expansion and shunt placement was avoided. Patients with MPS should be evaluated for craniosynostosis, and calvarial vault expansion may be considered as a viable treatment alternative to CSF shunting for elevated ICP in select patients.

Ocular manifestations and management recommendations of lysosomal storage disorders I: mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by inborn errors of glycosaminoglycan (GAG) metabolism. These diseases are classified by enzyme deficiency into seven groups: type I, II, III, IV, VI, VII, and IX. GAG accumulation leads to characteristic clinical features. Some ophthalmic findings that are characteristic of MPS diseases include corneal clouding, retinal degeneration, decreased electroretinogram wave amplitude, optic atrophy, papilledema, and glaucoma. Current treatments such as hematopoietic stem cell transplantation and enzyme replacement therapy have increased the life span of many MPS patients and created the need to improve management of ocular symptoms. This article aims to provide a comprehensive review of ocular manifestations and treatment options for the various types of MPS.