Search

Monosialotetrahexosylganglioside (GMI) gangliosidosis and Morquio type B (MorB) are two lysosomal storage disorders (LSDs) caused by the same enzyme deficiency, β‐galactosidase (βgal). GMI gangliosidosis, associated with GMI ganglioside accumulation, is a neurodegenerative condition characterized by psychomotor regression, visceromegaly, cherry red spot, and facial and skeletal abnormalities. MorB is characterized by prominent and severe skeletal deformities due to keratan sulfate (KS) accumulation. There are only a few reports on intermediate phenotypes between GMI gangliosidosis and MorB. The presentation of two new patients with this rare intermediate phenotype motivated us to review the literature, to study differences and similarities between GMI gangliosidosis and MorB, and to speculate about the possible mechanisms that may contribute to the differences in clinical presentation. In conclusion, we hypothesize that GMI gangliosidosis and MorB are part of one phenotypic spectrum of the same disease and that the classification of LSDs might need to be revised.

There is limited knowledge on the occurrence of respiratory manifestations and sleep-disordered breathing in particular in children with theMECP2duplication syndrome. Although sleep-disordered breathing and nocturnal hypoventilation are currently not cited as an important symptom in these children, we present three cases who all had an abnormal breathing during sleep. In view of the consequences associated with sleep apnea and hypoventilation, we advise to perform a polysomnography in children with MECP2 duplication. Different treatment modalities (ENT surgery, CPAP, and non-invasive ventilation) can be applied to successfully treat these conditions.

De novo missense variants in KCNH1 encoding Kv10.1 are responsible for two clinically recognisable phenotypes: Temple-Baraitser syndrome (TBS) and Zimmermann-Laband syndrome (ZLS). The clinical overlap between these two syndromes suggests that they belong to a spectrum of KCNH1-related encephalopathies. Affected patients have severe intellectual disability (ID) with or without epilepsy, hypertrichosis and distinctive features such as gingival hyperplasia and nail hypoplasia/aplasia (present in 20/23 reported cases).We report a series of seven patients with ID and de novo pathogenic KCNH1 variants identified by whole-exome sequencing or an epilepsy gene panel in whom the diagnosis of TBS/ZLS had not been first considered. Four of these variants, p.(Thr294Met), p.(Ala492Asp), p.(Thr493Asn) and p.(Gly496Arg), were located in the transmembrane domains S3 and S6 of Kv10.1 and one, p.(Arg693Gln), in its C-terminal cyclic nucleotide-binding homology domain (CNBHD). Clinical reappraisal by the referring clinical geneticists confirmed the absence of the distinctive gingival and nail features of TBS/ZLS.Our study expands the phenotypical spectrum of KCNH1-related encephalopathies to individuals with an attenuated extraneurological phenotype preventing a clinical diagnosis of TBS or ZLS. This subtype may be related to recurrent substitutions of the Gly496, suggesting a genotype–phenotype correlation and, possibly, to variants in the CNBHD domain.

De novo missense variants in

Histones mediate dynamic packaging of nuclear DNA in chromatin, a process that is precisely controlled to guarantee efficient compaction of the genome and proper chromosomal segregation during cell division and to accomplish DNA replication, transcription, and repair. Due to the important structural and regulatory roles played by histones, it is not surprising that histone functional dysregulation or aberrant levels of histones can have severe consequences for multiple cellular processes and ultimately might affect development or contribute to cell transformation. Recently, germline frameshift mutations involving the C-terminal tail of HIST1H1E, which is a widely expressed member of the linker histone family and facilitates higher-order chromatin folding, have been causally linked to an as-yet poorly defined syndrome that includes intellectual disability. We report that these mutations result in stable proteins that reside in the nucleus, bind to chromatin, disrupt proper compaction of DNA, and are associated with a specific methylation pattern. Cells expressing these mutant proteins have a dramatically reduced proliferation rate and competence, hardly enter into the S phase, and undergo accelerated senescence. Remarkably, clinical assessment of a relatively large cohort of subjects sharing these mutations revealed a premature aging phenotype as a previously unrecognized feature of the disorder. Our findings identify a direct link between aberrant chromatin remodeling, cellular senescence, and accelerated aging.

Spontaneous spinal epidural hematomas (SSEH) are a rare cause of spinal cord compression in childhood and especially in infancy. We reviewed the literature and describe a case of an 8-month-old boy with a large spontaneous cervico-thoracic epidural hematoma. With this review we want to detail the importance of early investigation, diagnosis and treatment in infants with SSEH. In our case the infant presented with irritability and crying and an ascending paralysis within four days. Magnetic resonance imaging (MRI) of the spine demonstrated an extensive epidural hematoma between C5 and L1, serious medullar compression and secondary cervical and thoracic medullar edema and hydromyelia. An emergency laminectomy was performed with evacuation of a well organized hematoma. There was a partial recuperation of the neurologic symptoms. Based on the scarce literature which only concerns seven case reports, SSEH is a rare cause of spinal compression in infancy. The presentation is often not specific and neurological symptoms are often lacking in the beginning. However early diagnosis with MRI and prompt neurosurgical intervention are important to improve outcome.

In a developmentally delayed girl with an autism spectrum disorder, Single nucleotide polymorphism (SNP) array analysis showed a de novo 280 kb deletion on chromosome 16q23.2 involving two genes, GAN and CMIP. Inactivating mutations in GAN cause the autosomal recessive disorder giant axonal neuropathy, not present in our patient. CMIP was recently implicated in the etiology of specific language impairment by genome-wide association analysis. It modulates phonological short-term memory and hence plays an important role in language acquisition. Overlaps of specific language impairment and autism have been debated in the literature regarding the phenotypical language profile as well as etiology. Our patient illustrates that haploinsufficiency of CMIP may contribute to autism spectrum disorders. Our finding further supports the existence of a genetic overlap in the etiology of specific language impairment and autism.

Down syndrome (DS) is one of the most common causes of mental retardation in children. Many children with DS suffer from neurologic problems, including seizures. Epileptic spasms (ES) are the most frequently reported seizure type. As in the general epilepsy population, ES are rather difficult to control with anti-epileptic drugs. Different treatment regimens have been proposed in the literature, most of them containing vigabatrin or steroids. We present 12 children with DS, who were seen and treated at the Antwerp University Hospital because of seizures. Eight of them presented with ES. Different treatment regimens were used, with varying outcome. This article summarizes our experience with epilepsy in children with DS, describing the different treatment options that were used. We found a poor outcome in these children, compared to most previous reports. Although steroids play an important role in the treatment of ES worldwide, we found a low success rate (8.3 %) of these drugs.

In a developmentally delayed girl with an autism spectrum disorder, Single nucleotide polymorphism (SNP) array analysis showed a de novo 280 kb deletion on chromosome 16q23.2 involving two genes, GAN and CMIP. Inactivating mutations in GAN cause the autosomal recessive disorder giant axonal neuropathy, not present in our patient. CMIP was recently implicated in the etiology of specific language impairment by genome-wide association analysis. It modulates phonological short-term memory and hence plays an important role in language acquisition. Overlaps of specific language impairment and autism have been debated in the literature regarding the phenotypical language profile as well as etiology. Our patient illustrates that haploinsufficiency of CMIP may contribute to autism spectrum disorders. Our finding further supports the existence of a genetic overlap in the etiology of specific language impairment and autism.

Objective Dravet syndrome is a severe epileptic encephalopathy beginning in infancy. The characteristic electroclinical picture is well known. With the discovery of SCN1A, molecular confirmation is possible in 75% of the patients. In approximately 70% a mutation is found and in 3–5% a copy number variant (CNV). CNVs frequently involve deletions, which not only contain SCN1A but the whole SCN gene cluster. This cluster contains five sodium channel genes (SCN3A, SCN2A, SCN1A, SCNC9A and SCN7A) along with GRB14 and GALNT3. The aim of this study was to determine whether patients with a SCN cluster deletion show a more severe form of the Dravet syndrome or have a specific continuous gene deletion syndrome. Methods We retrospectively reviewed the files of children with a deletion of the SCN gene cluster. Results We report six patients with a SCN cluster deletion (5 confirmed by aCGH, one with MLPA). All patients have a large de novo deletion (mean 5.6 Mb, SD 2.5). The mean age of presentation was 14.8 w (SD 7.3 w). Four infants presented with myoclonus, one with a febrile status epilepticus and one with an afebrile focal seizure with secondary generalization. Three had dysmorphic features and an abnormal development prior to the onset of convulsions. All patients showed a disastrous course with a severe mental retardation, hypotonia, failure to thrive and therapy resistant epilepsy in infancy. Two patients died around the age of one year, one at the age of 15 years. Three patients (8m, 20m and 4y of age) are still in follow-up. Conclusion Patients with a SCN cluster deletion frequently show a more severe form than the classic Dravet syndrome phenotype. The slightly earlier presentations with myoclonic seizures, abnormal development prior to the onset of convulsions, severe developmental delay or dead in infancy are suggestive for the SCN cluster deletion syndrome.

Opisthotonus is a relatively rare, but challenging neurological symptom of spasticity or dystonia that most often results from a dramatic event such as near-drowning. The classic treatment option for opisthotonus is the oral administration of medication such as benzodiazepines and baclofen. However, results with these medications are usually not very beneficial. Numerous studies however have shown that intrathecal treatment with baclofen (ITB) is an efficient and safe treatment for generalized therapy-resistant spasticity, even in children. In this retrospective study, we describe 11 children (mean age 9 years) with pronounced opisthotonus and quadriplegia caused by different types of acquired lesions who were treated with intrathecal baclofen. Results show that in addition to an expected decrease in muscle tonus, there was also a clear improvement in patient comfort and nursing. A remarkable weight gain was observed in most patients, even when calorie intake did not change. This increase in weight might be due to a reduction in energy expenditure as a result of the decrease in spasticity. Intrathecal treatment with baclofen should be considered in every child with opisthotonus.