Spinal extradural arachnoid cysts in lymphedema-distichiasis syndrome

Prenatal dispositions and genetic analysis of monozygotic female twins with suprasellar cysts and hydrocephalus: A case report

INTRODUCTION

We present a unique case of monozygotic female twins with virtually identical clinical and radiological presentations of supratentorial hydrocephalus and cystic formations from the suprasellar cistern.

DISCUSSION

Evaluating genetic predispositions and prenatal exposures is crucial for hydrocephalus in twins. Familial cases imply a genetic contribution to the development of these anomalies, including chromosomal abnormalities and specific variants linked to arachnoid cyst formation in various syndromes. Extensive genetic analyses found no pathogenic variants in the twins. Prenatal exposure to anti-epileptic medication was known during pregnancy and may be associated with fetal abnormalities, but not central nervous system (CNS) malformations, and was therefore not considered the cause of the condition in the twins. The twins presenting simultaneously with hydrocephalus caused by suprasellar cysts (SAC) underwent a two-step surgical management: initial ventriculoperitoneal shunt (VPS) placement followed by fenestration. Postoperative imaging showed cyst reduction, but a secondary VPS was necessary in both cases.

CONCLUSION

Genetic analysis is less likely to identify a monogenic etiology in non-syndromic cases of SACs, which are assumed to be multifactorial. There is no established evidence linking a teratogenic effect of anti-epileptic drugs to CNS malformations. Moreover, the surgical treatment of this complex condition constitutes a point of discussion.

Familial and syndromic forms of arachnoid cyst implicate genetic factors in disease pathogenesis

Arachnoid cysts (ACs) are the most common space-occupying lesions in the human brain and present significant challenges for clinical management. While most cases of ACs are sporadic, nearly 40 familial forms have been reported. Moreover, ACs are seen with increased frequency in multiple Mendelian syndromes, including Chudley-McCullough syndrome, acrocallosal syndrome, and autosomal recessive primary ciliary dyskinesia. These findings suggest that genetic factors contribute to AC pathogenesis. However, traditional linkage and segregation approaches have been limited in their ability to identify causative genes for ACs because the disease is genetically heterogeneous and often presents asymptomatically and sporadically. Here, we comprehensively review theories of AC pathogenesis, the genetic evidence for AC formation, and discuss a different approach to AC genomics that could help elucidate this perplexing lesion and shed light on the associated neurodevelopmental phenotypes seen in a significant subset of these patients.

Deleterious fibronectin type III-related gene variants may induce a spinal extradural arachnoid cyst: an exome sequencing study of identical twin cases

PURPOSE

Despite numerous studies, the etiology of spinal extradural arachnoid cyst (SEDAC), a lesion associated with neurological symptoms, remains unknown. In this genomic twin study, we investigated the genetic etiology of SEDACs.

METHODS

The subjects were identical twins who developed notably similar SEDACs at the same vertebral level. Accordingly, we performed whole-exome sequencing analyses of genomic material from the twins and their parents using a next-generation sequencer. Additionally, we determined their detailed family history and analyzed the family pedigree.

RESULTS

The pedigree analysis suggested the potential presence of SEDACs in certain family members, indicating a genetic disease. Sequenced data were analyzed and filtered using a purpose-built algorithm, leading to the identification of 155 novel single-nucleotide polymorphisms (SNPs), of which 118 encoded missense or nonsense variants. A functional analysis of the proteins encoded by these SNP alleles revealed strong enrichment for the fibronectin type III (FN3) protein domain (q = 0.00576). Specifically, the data indicated that a missense variant affecting the FN3 protein domain of fibronectin 1 (FN1, p.P969S) can be the causal mutation underlying the SEDACs.

CONCLUSION

The data suggest that deleterious mutations in fibronectin-related genes may cause SEDACs. In particular, it was suspected that a variant of FN1 may be the cause of the SEDACs in the twin cases studied herein. Detailed studies with a larger number of cases are needed.

Occurrence of spinal extradural arachnoid cysts in a child with concomitant intracranial midline abnormalities: case report

Spinal extradural arachnoid cysts (SEACs) are uncommon spinal lesions that may cause myelopathy, most frequently in the 2nd decade of life. There are multiple theories of their pathogenesis, and associated entities include spinal trauma, spina bifida, and the lymphedema-distichiasis syndrome. The authors report the case of an otherwise healthy, developmentally normal 13-year-old boy who presented with multiple SEACs. Upon further neuroimaging workup, he was found to have an asymptomatic retrocerebellar arachnoid cyst, cavum septi pellucidi, and cavum vergae. Three contiguous but separate spinal cysts were identified intraoperatively, and they were completely excised with closure of the dural defects. The patient recovered motor and sensory function of the lower extremities. This collection of uncommon neuroimaging findings provides important clues to the pathogenesis of the disease and guides the optimal management of patients with SEACs. The unusual presentation of SEACs, together with uncommon midline abnormalities, provides further evidence of their congenital, midline origin. Therefore, it is reasonable to pursue imaging of the brain in atypical cases of SEACs.

Crystal Structure of FOXC2 in Complex with DNA Target

Forkhead transcription factor C2 (FOXC2) is a transcription factor regulating vascular and lymphatic development, and its mutations are linked to lymphedema-distichiasis syndrome. FOXC2 is also a crucial regulator of the epithelial-mesenchymal transition processes essential for tumor metastasis. Here, we report the crystal structure of the FOXC2-DNA-binding domain in complex with its cognate DNA. The crystal structure provides the basis of DNA sequence recognition by FOXC2 for the T/CAAAC motif. Helix 3 makes the majority of the DNA-protein interactions and confers the DNA sequence specificity. The computational energy calculation results also validate the structural observations. The FOXC2 and DNA complex structure provides a detailed picture of protein and DNA interactions, which allows us to predict its DNA recognition specificity and impaired functions in mutants identified in human patients.

Familial arachnoid cysts: a review of 35 families

INTRODUCTION

Arachnoid cysts are commonly considered congenital lesions, but this has not been proven. With the development of neuroimaging and DNA testing technology, more cases of familial arachnoid cysts have been reported. Herein, we review such cases.

MATERIALS AND METHODS

The PubMed, Embase, and Web of Science databases were searched for case reports of arachnoid cysts published through April 2018. Case reports were included only if two or more related patients were diagnosed with an arachnoid cyst by neuroimaging or intraoperatively. For each report, the following data were extracted: first author name, date of publication, number of families, number of patients, location of the arachnoid cysts, patient age, patient sex, and genetic mutations and associated disease.

RESULTS

Our searches identified 33 case reports involving 35 families and 115 patients. The locations of arachnoid cysts were similar in 25 of the 35 families. Spinal extradural arachnoid cysts were reported most often, followed by arachnoid cysts in the middle fossa and posterior fossa. A left-sided predominance was noticed for arachnoid cysts of the middle fossa. Mutation of the FOXC2 gene was reported most often, and arachnoid cysts may be associated with mutations on chromosome 16.

CONCLUSIONS

Although the origin of arachnoid cysts is believed to have a genetic component by some researchers, the genes associated with arachnoid cysts remain unknown. Unfortunately, the evidence remains insufficient.

A screening method to distinguish syndromic from sporadic spinal extradural arachnoid cyst

BACKGROUND

Spinal extradural arachnoid cyst (SEDAC) is a cystic lesion that protrudes into the epidural space from a small dural defect. Early diagnosis of SEDAC is important because its expansion causes neurological damage. Two types of SEDAC, syndromic and sporadic, are present. Syndromic SEDAC is inherited as a part of lymphedema-distichiasis syndrome caused by mutations in the FOXC2 gene; however, it is often mistaken as sporadic because of low penetrance. It is not reasonable to conduct a genetic testing for all SEDAC patients and their family members. The aim of this study is to establish an effective screening method to distinguish syndromic SEDAC from sporadic SEDAC.

METHODS

We performed a retrospective review of medical records and imaging studies of 29 subjects who were diagnosed with SEDAC. Clinical features, family history and magnetic resonance imaging (MRI) were analyzed. Mutations in FOXC2 were examined by Sanger-sequencing of the entire coding region of the genes. SEDAC having a mutation in FOXC2 gene was defined with syndromic SEDAC.

RESULTS

Eleven subjects had a heterozygous mutation in FOXC2. They were all familial and hence syndromic SEDAC. Only one proband had known family history of SEDAC at diagnosis. MRI findings and physical examinations, especially eye and leg examinations, were quite useful to screen syndromic SEDAC. Physical examination often showed accompanying lymphedema and distichiasis in syndromic SEDAC. Syndromic SEDAC tended to have multiple cysts out of the thoracolumbar area.

CONCLUSIONS

We established an effective screening method based on physical examinations and MRI findings.

Symptomatic spinal extradural arachnoid cyst with cord compression in a family: case report

A family with familial spinal extradural arachnoid cyst is presented. A 14-year-old boy had an extensive T-8 through L-2 dorsal extradural arachnoid cyst with spinal cord compression and slowly progressive myelopathy. His mother had presented 4 years earlier with acute excruciating back pain due to the combination of a lumbar extradural arachnoid cyst at L2–4 and an extruded disc at L3–4. The literature is reviewed in light of the pathogenesis, imaging, and surgical technique required for treatment.

Renal anomalies and lymphedema distichiasis syndrome. A rare association?

Lymphedema distichiasis syndrome (LDS) is a rare, autosomal dominant genetic condition, characterized by lower limb lymphedema and distichiasis. Other associated features that have been reported include varicose veins, cleft palate, congenital heart defects, and ptosis. We update a previously reported family with a pathogenic variant in FOXC2 (c.412-413insT) where five affected individuals from the youngest generation had congenital renal anomalies detected on prenatal ultrasound scan. These included four fetuses with hydronephrosis and one with bilateral renal agenesis. A further child with LDS had prominence of the left renal pelvis on postnatal renal ultrasound. We also describe a second family in whom the proband and his affected son had congenital renal anomalies; left ectopic kidney, right duplex kidney, and bilateral duplex collecting systems with partial duplex kidney with mild degree of malrotation, respectively. Foxc2 is expressed in the developing kidney and therefore congenital renal anomalies may well be associated, potentially as a low penetrance feature. We propose that all individuals diagnosed with LDS should have a baseline renal ultrasound scan at diagnosis. It would also be important to consider the possibility of renal anomalies during prenatal ultrasound of at risk pregnancies, and that the presence of hydronephrosis may be an indication that the baby is affected with LDS.

Identification of HOXD4 Mutations in Spinal Extradural Arachnoid Cyst

Spinal extradural arachnoid cyst (SEDAC) is a cyst in the spinal canal that protrudes into the epidural space from a defect in the dura mater and leads to neurological disturbances. We previously showed that familial SEDAC is caused by FOXC2 mutation; however, the causal gene of sporadic SEDAC has not been identified. To identify the causal gene of sporadic SEDAC, we performed whole exome sequencing for 12 subjects with sporadic SEDAC and identified heterozygous HOXD4 loss-of-function mutations in three subjects. HOXD4 haplo-insufficiency causes SEDAC and a transcriptional network containing HOXD4 and FOXC2 is involved in the development of the dura mater and the etiology of SEDAC.

A novel FOXC2 mutation in spinal extradural arachnoid cyst

Spinal extradural arachnoid cyst (SEDAC) is a cyst in the spinal canal, which causes spinal cord compression and subsequent neurological damage. We previously identified two FOXC2 mutations in two SEDAC families. The FOXC2 mutations have been shown to be responsible for lymphedema-distichiasis syndrome (LDS), which includes SEDAC as an occasionally associated phenotype. We encountered a non-familial patient with SEDAC associated with LDS, and identified a novel nonsense mutation in FOXC2, c.349C>T (p.Q117*).

FOXC2 mutations in familial and sporadic spinal extradural arachnoid cyst

Spinal extradural arachnoid cyst (SEDAC) is a cyst in the spinal canal that protrudes into the epidural space from a defect in the dura mater. Most cases are sporadic; however, three familial SEDAC cases have been reported, suggesting genetic etiological factors. All familial cases are associated with lymphedema-distichiasis syndrome (LDS), whose causal gene is FOXC2. However, FOXC2 mutation analysis has been performed in only 1 family, and no mutation analysis has been performed on sporadic (non-familial) SEDACs. We recruited 17 SEDAC subjects consisting of 2 familial and 7 sporadic cases and examined FOXC2 mutations by Sanger sequencing and structural abnormalities by TaqMan copy number assay. We identified 2 novel FOXC2 mutations in 2 familial cases. Incomplete LDS penetrance was noted in both families. Four subjects presented with SEDACs only. Thus, SEDAC caused by the heterozygous FOXC2 loss-of-function mutation should be considered a feature of LDS, although it often manifests as the sole symptom. Seven sporadic SEDAC subjects had no FOXC2 mutations, no symptoms of LDS, and showed differing clinical characteristics from those who had FOXC2 mutations, suggesting that other gene(s) besides FOXC2 are likely to be involved in SEDAC.