Compound Heterozygous ROBO3 Mutation in Two Siblings Presenting with Horizontal Gaze Palsy without Scoliosis: Case-Based Review.

Horizontal gaze palsy with progressive scoliosis (HGPPS) is a rare, autosomal recessively inherited disorder characterized by a congenital absence of conjugated horizontal eye movements with progressive scoliosis developing in childhood and adolescence. HGPPS is caused by mutations of the ROBO3 gene that disrupts the midline crossing of the descending corticospinal and ascending lemniscal sensory tracts in the medulla. We present two siblings, 5-year-old and 2-year-old boys with HGPPS, from non-consanguineous parents. The older brother was brought for the evaluation of moderate psychomotor retardation. He had bilateral horizontal gaze palsy with preserved vertical gaze and convergence. Scoliosis was absent. Cranial MRI showed brainstem abnormalities, and diffusion tensor imaging showed absent decussation of cortico-spinal tracts in the medulla. Clinical diagnosis of HGPPS was confirmed by sequencing of ROBO3 gene, IVS4-1G > A (c.767-1G > A) and c.328_329delinsCCC (p.Asp110Profs*57) compound heterozygous variations were found, and segregated in parents. The younger boy was first reported at 16 months of age and had the same clinical and neuroradiological findings, unlike mild psychomotor retardation. ROBO3 gene analysis showed the same variants in his brother. Our cases show the importance of evaluating eye movements in children with neurodevelopmental abnormalities and looking for brainstem abnormalities in children with bilateral horizontal gaze palsy.

Phenotypical spectrum of SACS variants: Neuromuscular perspective of a complex neurodegenerative disorder.

OBJECTIVES: Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is caused by the SACS gene variants. Main clinical features include early-onset and progressive cerebellar ataxia, spasticity, sensorimotor polyneuropathy. However, the phenotypic spectrum expanded with the increased availability of next-generation sequencing methods. MATERIALS AND METHODS: Herein, we describe the clinical features of nine patients from seven unrelated families with SACS variants from the cohort of the Neuromuscular Disorders Unit of the Neurology Department of the Istanbul University, Istanbul Faculty of Medicine. RESULTS: Seven patients were male. Seven patients in our cohort had disease onset in the first decade of life. Eight patients were born to consanguineous marriages. Distal weakness in the lower limbs was a prominent feature in all of our patients. Seven patients had ataxia, and six patients had spasticity. Interestingly, one patient showed an isolated Charcot-Marie-Tooth-like phenotype. Five patients showed sensorimotor demyelinating polyneuropathy in the nerve conduction studies. Linear pontine hypointensity was the most frequent cranial magnetic resonance imaging (MRI) abnormality. Two patients with a later disease onset had a homozygous c.11542_11544delATT (p.Ile3848del) variant. The rest of the identified variants were scattered throughout the SACS gene. CONCLUSIONS: Atypical clinical features in our patients highlight that the phenotypic spectrum of ARSACS can be observed in a wide range.

NGLY1 mutation causes neuromotor impairment, intellectual disability, and neuropathy.

N-glycanase 1 (NGLY1) is a conserved enzyme that is responsible for the deglycosylation of misfolded N-glycosylated proteins in the cytoplasm prior to their proteasome-mediated degradation. Disruption of this degradation process has been associated with various neurologic diseases including amyotrophic lateral sclerosis and Parkinson's disease. Here, we describe two siblings with neuromotor impairment, apparent intellectual disability, corneal opacities, and neuropathy who were found to possess a novel homozygous frame-shift mutation due to a 4 base pair deletion in NGLY1 (c.1533_1536delTCAA, p.Asn511LysfsX51). We hypothesize that this mutation likely limits the capability of neuronal cells to respond to stress due to accumulation of misfolded proteins, thereby impairing their survival and resulting in progressive loss of neurological function.

Autosomal recessive spastic tetraplegia caused by AP4M1 and AP4B1 gene mutation: expansion of the facial and neuroimaging features.

Adaptor protein complex-4 (AP4) is a component of intracellular transportation of proteins, which is thought to have a unique role in neurons. Recently, mutations affecting all four subunits of AP4 (AP4M1, AP4E1, AP4S1, and AP4B1) have been found to cause similar autosomal recessive phenotype consisting of tetraplegic cerebral palsy and intellectual disability. The aim of this study was analyzing AP4 genes in three new families with this phenotype, and discussing their clinical findings with an emphasis on neuroimaging and facial features. Using homozygosity mapping followed by whole-exome sequencing, we identified two novel homozygous mutations in AP4M1 and a homozygous deletion in AP4B1 in three pairs of siblings. Spastic tetraplegia, microcephaly, severe intellectual disability, limited speech, and stereotypic laughter were common findings in our patients. All patients also had similar facial features consisting of coarse and hypotonic face, bitemporal narrowing, bulbous nose with broad nasal ridge, and short philtrum which were not described in patients with AP4M1 and AP4B1 mutations previously. The patients presented here and previously with AP4M1, AP4B1, and AP4E1 mutations shared brain abnormalities including asymmetrical ventriculomegaly, thin splenium of the corpus callosum, and reduced white matter volume. The patients also had hippocampal globoid formation and thin hippocampus. In conclusion, disorders due to mutations in AP4 complex have similar neurological, facial, and cranial imaging findings. Thus, these four genes encoding AP4 subunits should be screened in patients with autosomal recessive spastic tetraplegic cerebral palsy, severe intellectual disability, and stereotypic laughter, especially with the described facial and cranial MRI features.

An association analysis at 2q36 reveals a new candidate susceptibility gene for juvenile absence epilepsy and/or absence seizures associated with generalized tonic-clonic seizures.

PURPOSE: To further evaluate the previously shown linkage of absence epilepsy (AE) to 2q36, both in human and WAG/Rij absence rat models, a 160-kb region at 2q36 containing eight genes with expressions in the brain was targeted in a case-control association study involving 205 Turkish patients with AE and 219 controls. METHODS: Haplotype block and case-control association analysis was carried out using HAPLOVIEW 4.0 and inhibin alpha subunit (INHA) gene analysis by DNA sequencing. KEY FINDINGS: An association was found between the G allele of rs7588807 located in the INHA gene and juvenile absence epilepsy (JAE) syndrome and patients having generalized tonic-clonic seizures (GTCS) with p-values of 0.003 and 0.0002, respectively (uncorrected for multiple comparisons). DNA sequence analysis of the INHA gene in 110 JAE/GTCS patients revealed three point mutations with possible damaging effects on inhibin function in three patients and the presence of a common ACTC haplotype (H1) with a possible dominant protective role conferred by the T allele of rs7588807 with respective p-values of 0.0005 and 0.0014. SIGNIFICANCE: The preceding findings suggest that INHA could be a novel candidate susceptibility gene involved in the pathogenesis of JAE or AE associated with GTCS.

Etiologies of seizures in young children admitted to an inner city hospital in a developing country.

OBJECTIVES: In this study, we aimed to document the etiologies of seizures in young children in an urban reference hospital in a developing county. METHODS: One hundred fifty-six children (aged 1 to 24 months) hospitalized in an inner city hospital between 2000 and 2004 with seizures were evaluated retrospectively in terms of etiologies and some risk factors. RESULTS: The seizures were cryptogenic (presumed symptomatic) in 9 (5%) patients, symptomatic in 29 (18.6%) patients, and situation-related (febrile, hypocalcemic, hyponatremic, and hypoglycemic) in 118 (75.6%) patients. Hypocalcemia due to rickets was the leading cause (25.6%) of afebrile seizures in this population. CONCLUSIONS: Hypocalcemia has an important place in the etiology of afebrile seizures among our patients unlike in many developed countries. So, nutritional status should be kept in mind while evaluating the etiologies of seizures in young children in developing countries.

Epilepsy in vacuolating megalencephalic leukoencephalopathy with subcortical cysts.

Vacuolating megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a disorder characterised by acquired macrocephaly, developmental motor delay of varying degrees, slowly progressive cerebellar and pyramidal signs, and initially preserved intellectual function. More than 60% of the published cases had epileptic seizures. In this study, we analysed the seizures and EEG findings of nine patients with MLC. Six patients (66.6%) with moderate to severe neurological impairment had epilepsy, four with partial and two with generalised seizures. The EEG of five epileptic patients revealed epileptogenic foci over the temporal, frontal and parietal regions with variable predominance during waking and sleep. The facilitation of spike-and-wave paroxysms by eye closure, by intermittent photic stimulation and by hyperventilation were determined in four patients. Four patients also showed abnormalities in the background activity. In conclusion, we think that epilepsy is a significant component of MLC compared to the other leukodystrophies. The elucidation of the underlying molecular defect may explain the unusual pathogenetic relation between this leukoencephalopathy and the associated seizures.