Neuronal Ceroid Lipofuscinosis: The Multifaceted Approach to the Clinical Issues, an Overview

Transcriptomic analyses of human brains with Alzheimer's disease identified dysregulated epilepsy-causing genes

BACKGROUND & OBJECTIVE

Alzheimer's Disease (AD) patients at multiple stages of disease progression have a high prevalence of seizures. However, whether AD and epilepsy share pathophysiological changes remains poorly defined. In this study, we leveraged high-throughput transcriptomic data from sporadic AD cases at different stages of cognitive impairment across multiple independent cohorts and brain regions to examine the role of epilepsy-causing genes.

METHODS

Epilepsy-causing genes were manually curated, and their expression levels were analyzed across bulk transcriptomic data from three AD cohorts and three brain regions. RNA-seq data from sporadic AD and control cases from the Knight ADRC, MSBB, and ROSMAP cohorts were processed and analyzed under the same analytical pipeline. An integrative clustering approach employing machine learning and multi-omics data was employed to identify molecularly defined profiles with different cognitive scores.

RESULTS

We found several epilepsy-associated genes/pathways significantly dysregulated in a group of AD patients with more severe cognitive impairment. We observed 15 genes consistently downregulated across the three cohorts, including sodium and potassium channels genes, suggesting that these genes play fundamental roles in cognitive function or AD progression. Notably, we found 25 of these genes dysregulated in earlier stages of AD and become worse with AD progression.

CONCLUSION

Our findings revealed that epilepsy-causing genes showed changes in the early and late stages of AD progression, suggesting that they might be playing a role in AD progression. We can not establish directionality or cause-effect with our findings. However, changes in the epilepsy-causing genes might underlie the presence of seizures in AD patients, which might be present before or concurrently with the initial stages of AD.

Defective anterograde protein-trafficking contributes to endoplasmic reticulum-stress in a CLN1 disease model

Lysosomal storage disorders (LSDs) represent 70 inherited metabolic diseases, in most of which neurodegeneration is a devastating manifestation. The CLN1 disease is a fatal neurodegenerative LSD, caused by inactivating mutations in the CLN1 gene encoding palmitoyl-protein thioesterase-1 (PPT1). S-palmitoylation, a reversable posttranslational modification by saturated fatty acids (generally palmitate) facilitates endosomal trafficking of many proteins, especially in the brain. While palmitoyl-acyltransferases (called ZDHHCs) catalyze S-palmitoylation, depalmitoylation is mediated by palmitoyl-protein thioesterases (PPTs). We previously reported that in Cln1-/- mice, which mimic human CLN1-disease, endoplasmic reticulum (ER)-stress leads to unfolded protein response (UPR) contributing to neurodegeneration. However, the mechanism underlying ER-stress has remained elusive. The anterograde (ER to Golgi) protein-trafficking is mediated via COPII (coat protein complex II) vesicles, whereas the retrograde transport (Golgi to ER) is mediated by COPI vesicles. We hypothesized that dysregulated anterograde protein-trafficking causing stagnation of proteins in the ER leads to ER-stress in Cln1-/- mice. We found that the levels of five COPII vesicle-associated proteins (i.e. Sar1, Sec23, Sec24, Sec13 and Sec31) are significantly higher in the ER-fractions of cortical tissues from Cln1-/- mice compared with those from their WT littermates. Remarkably, all COPII proteins, except Sec13, undergo S-palmitoylation. Moreover, CLN8, a Batten disease-protein, requires dynamic S-palmitoylation (palmitoylation-depalmitoylation) for ER-Golgi trafficking. Intriguingly, Ppt1-deficiency in Cln1-/- mice impairs ER-Golgi trafficking of Cln8-protein along with several other COPII-associated proteins. We propose that impaired anterograde trafficking causes excessive accumulation of proteins in the ER causing ER-stress and UPR contributing to neurodegeneration in CLN1 disease.

UNRAVELING CLN7 disease: the distinct roles of two close MFSD8/CLN7 splice variants in phenotypic expression

CLN7 is a lysosomal storage disease caused by pathogenic variants in the MFSD8/CLN7 gene. Typically neurodegenerative, patients present seizures and developmental delay since 2-6 years of age and a rapid psychomotor, verbal, and visual deterioration that leads to premature death. However, 'atypical' cases have also been reported. Although more than 80 DNA variants in the MFSD8/CLN7 gene have been reported, no data about a genotype/phenotype correlation is available. Here, we analyze five 'classical' and 'atypical' CLN7 patients by molecular and computational methods. Four variants have been found: c.103C > T (p.Arg35*, pathogenic), c.1394G > A (p.Arg465Gln, pathogenic), c.863 + 1G > A (likely pathogenic), and c.863 + 4A > G (of uncertain significance). Both splice variants showed altering of the splicing process on a minigene reporter assay. Furthermore, exon 8 was deleted in the MFSD8/CLN7 cDNA of blood samples from two patients carrying the splicing variants, demonstrating their effect. The c.863 + 4A > G variant also showed a residual wildtype MFSD8/CLN7 expression and, thus, explaining the milder phenotype. Finally, a clustered geographical distribution of the c.103C > T and c.863 + 4A > G variants was observed in the northeast and center of Argentina, respectively. Our data confirm the pathogenicity of the c.863 + 1G > A variant and reclassify the c.863 + 4A > G variant as pathogenic by adding experimental data, offering new information for a precise prognosis, and expanding the genetic and epidemiological spectrum of CLN7 in the South American region. Ultimately, we seek to raise awareness about the existence of this pathology in the region to reduce the so-called 'diagnostic odyssey' in pediatric patients.

Neuronal ceroid lipofuscinosis type 11 in early childhood

Neuronal ceroid lipofuscinosis comprises a group of heterogeneous lysosomal storage disorders characterised by the accumulation of autofluorescent ceroid lipopigment, leading to progressive neurological deterioration. Based on the gene-based classification of NCL, 14 loci have been identified to date. This report describes a case of a man in his early 20s, born to second-degree consanguineous parents, with disease onset at 6 years of age. The patient presented with progressive vision loss secondary to retinal degeneration and recurrent seizures. Genetic testing using next-generation whole exome sequencing revealed a homozygous pathogenic mutation in the progranulin gene (GRN) in exon 12 (c.1469delp. Val490GlyfsTer27), confirming a diagnosis of CLN type-11 (OMIM#614706).

Expanded Phenotype of the Cln6nclf Mouse Model

Neuronal ceroid lipofuscinoses (NCLs) are a group of autosomal recessive neurogenetic disorders caused by mutations in 14 different genes. CLN6 disease manifests as variant late-infantile NCL (vLINCL) or as an adult variant. In childhood, symptoms include speech delay, vision loss, cognitive and motor decline, seizures, and early death. An in-depth characterization of a naturally occurring Cln6 mutant mouse (Cln6nclf) is presented, with implications for translational research. The expanded phenotype provides data showing early death, vision loss, and motor deficits in male and female Cln6nclf mice. Diminished visual acuity in Cln6nclf mice was noted at 28 weeks of age, but the pathological loss of retinal layers began as early as 2 weeks or postnatal day 14 (P14). Apoptosis was confirmed by TUNEL staining in the Cln6nclf mouse brain at P8 and in the retina at P12. A peak in glial fibrillary acidic protein (GFAP) expression was established as a normal developmental phenomenon in the wild-type and Cln6nclf mouse brain cerebellum and the CA2-CA3 regions of the hippocampus at P8. In Cln6nclf mice, GFAP levels were elevated at P12 in the cerebellum and hippocampus. In the retina, a developmental peak in gliosis was absent, with increased astrogliosis noted at P6 and P8 in female and male Cln6nclf mice, respectively. This highlights the lack of a sex-dependent response in wild-type mice. These novel data position the Cln6nclf mouse model as a useful tool for screening potential therapeutics for human CLN6 disease.

A Rare Case Report of Neurodegenerative Disease With Oro-Dental Trauma

Batten disease, also known as Spielmeyer-Vogt-Sjögren-Batten disease, is a rare and deadly autosomal recessive neurodegenerative disease. It is the most prevalent type among a group of diseases known as neuronal ceroid lipofuscinoses (NCLs).  The patient, a 31-year-old woman, presented to the Oral Medicine and Radiology Department with the primary complaint of knocking out her upper front teeth after she had suffered a seizure and fell out of bed onto the floor. She has Batten disease, according to her medical history (NCL2). The diagnosis and treatment of an oro-dental issue are presented in this instance. As an oral physician, understanding Batten disease is crucial because it requires a multidisciplinary approach to manage the oral health issues associated with it. Early intervention and continuous support are essential to maintaining the well-being of affected individuals.

Enzyme Replacement Therapy in CLN2-Associated Retinopathy

Neuronal ceroid lipofuscinoses, also known as Batten disease, are comprised of a group of genetically heterogenous neurodegenerative conditions, characterized by dementia, epilepsy, motor deterioration, and blindness. The underlying pathology is a dysregulation of lysosomal catabolic protein metabolism, resulting in an accumulation of lipofuscein-like material within the lysosomes in neuronal tissue, which ultimately leads to atrophy in the central nervous system and in the retina. Ceroid lipofuscinosis type 2 (CLN2) is caused by biallelic pathogenic variants in the TPP1 gene, encoding lysosomal tripeptidyl peptidase 1 (TPP-1). The classic late-infantile phenotype of CLN2 disease has an age of onset between 2 and 4 years and manifests with seizures and speech delay, followed by progressive cognitive and motor decline, vision loss, and early death. Vision loss occurs secondary to retinal degeneration and begins in the perifoveal ellipsoid zone, leading to bull's eye maculopathy, followed by generalized retinal thinning. In 2017, an intracerebroventricular enzyme replacement therapy (ERT) using recombinant human TPP1 (rhTPP1), cerliponase alfa, was approved as a disease-modifying treatment for CLN2 disease. The therapy slows psychomotor decline but fails to prevent loss of vision. In a canine model of CLN2 disease, intravitreal rhTPP1 was shown to halt retinal degeneration. A prospective, interventional, controlled, open-label compassionate-use study evidenced safety of 0.2 mg intravitreal rhTPP1 every 8 weeks in humans and its efficacy in reducing the rate of macular volume loss in patients who were still in the degenerative phase. One ongoing clinical phase I/II study is investigating the safety and efficacy of intravitreal rhTPP1 at 4 weekly intervals over 24 months (NCT05152914); another clinical phase II dose escalation trial is planned. In this review, we summarize the current knowledge on ERT for CLN2 retinopathy, complemented with our own experience from an individual treatment. The treatment now appears to be safe and markedly delays retinal degeneration, thereby preserving visual function and increasing the quality of life of the patient. This could be particularly relevant for those patients who were started on intracerebroventricular ERT early and still have good motor and language function. For this patient population, intravitreal ERT could be a valuable bridging therapy until other therapies such as gene therapy become available.

Transcriptomic analyses of human brains with Alzheimer's disease identified dysregulated epilepsy-causing genes

Background & Objective

Alzheimer's Disease (AD) patients at multiple stages of disease progression have a high prevalence of seizures. However, whether AD and epilepsy share pathophysiological changes remains poorly defined. In this study, we leveraged high-throughput transcriptomic data from sporadic AD cases at different stages of cognitive impairment across multiple independent cohorts and brain regions to examine the role of epilepsy-causing genes.

Methods

Epilepsy-causing genes were manually curated, and their expression levels were analyzed across bulk transcriptomic data from three AD cohorts and three brain regions. RNA-seq data from sporadic AD and control cases from the Knight ADRC, MSBB, and ROSMAP cohorts were processed and analyzed under the same analytical pipeline. An integrative clustering approach employing machine learning and multi-omics data was employed to identify molecularly defined profiles with different cognitive scores.

Results

We found several epilepsy-associated genes/pathways significantly dysregulated in a group of AD patients with more severe cognitive impairment. We observed 15 genes consistently downregulated across the three cohorts, including sodium and potassium channels, suggesting that these genes play fundamental roles in cognitive function or AD progression. Notably, we found 25 of these genes dysregulated in earlier stages of AD and become worse with AD progression.

Conclusion

Our findings showed that epilepsy-causing genes showed changes in the early and late stages of AD progression, suggesting that they might be playing a role in AD progression. We can not establish directionality or cause-effect with our findings. However, changes in the epilepsy-causing genes might underlie the presence of seizures in AD patients, which might be present before or concurrently with the initial stages of AD.

Persistent low concentrations of antiepileptics in a critically ill paediatric patient: an example of multiple potential drug interactions

A middle childhood boy with epilepsy exhibited persistent low concentrations of valproic acid, lamotrigine and topiramate for over 1 month, primarily due to pharmacokinetic interactions involving fosphenytoin, meropenem and phenobarbital. Awareness of these clinically significant interactions is crucial for ensuring effective seizure control. However, further research is needed to establish optimal evidence-based treatment strategies in complex paediatric cases.

Targeting Ferroptosis in Rare Neurological Disorders Including Pediatric Conditions: Innovations and Therapeutic Challenges

Ferroptosis, characterized by iron dependency and lipid peroxidation, has emerged as a key mechanism underlying neurodegeneration in rare neurological disorders. These conditions, often marked by significant therapeutic gaps and high unmet medical needs, present unique challenges for intervention development. This review examines the involvement of ferroptosis in rare neurological disease pathogenesis, focusing on its role in oxidative damage and neuronal dysfunction. We explore recent pharmacological advancements, including iron chelators, lipid peroxidation blockers, and antioxidant-based strategies, designed to target ferroptosis. While these approaches show promise, challenges such as disease heterogeneity, limited diagnostic tools, and small patient cohorts hinder progress. Furthermore, we discuss the translational and regulatory barriers to implementing ferroptosis-based therapies in clinical practice. By addressing these obstacles and fostering innovative solutions, this review underscores the potential of ferroptosis-targeting strategies to revolutionize treatment paradigms for rare neurological disorders.

Syndromic Retinitis Pigmentosa: A Narrative Review

Retinitis pigmentosa (RP) encompasses inherited retinal dystrophies, appearing either as an isolated eye condition or as part of a broader systemic syndrome, known as syndromic RP. In these cases, RP includes systemic symptoms impacting other organs, complicating diagnosis and management. This review highlights key systemic syndromes linked with RP, such as Usher, Bardet-Biedl, and Alström syndromes, focusing on genetic mutations, inheritance, and clinical symptoms. These insights support clinicians in recognizing syndromic RP early. Ocular signs like nystagmus and congenital cataracts may indicate systemic disease, prompting genetic testing. Conversely, systemic symptoms may necessitate eye exams, even if vision symptoms are absent. Understanding the systemic aspects of these syndromes emphasizes the need for multidisciplinary collaboration among ophthalmologists, pediatricians, and other specialists to optimize patient care. The review also addresses emerging genetic therapies aimed at both visual and systemic symptoms, though more extensive studies are required to confirm their effectiveness. Overall, by detailing the genetic and clinical profiles of syndromic RP, this review seeks to aid healthcare professionals in diagnosing and managing these complex conditions more effectively, enhancing patient outcomes through timely, specialized intervention.

Neuronal ceroid lipofuscinosis 11 (CLN11) presenting with early-onset cone-rod dystrophy and learning difficulties

Neuronal Ceroid Lipofuscinosis 11 (CLN11) is an ultra-rare subtype of adult-onset Neuronal Ceroid Lipofuscinosis. Its phenotype is variable and not fully known. A 21-year-old man was evaluated in our neurogenetic outpatient clinic for early onset complex phenotype, including learning difficulties, cerebellar ataxia, cone-rod dystrophy, epilepsy, and dystonia. The patient was submitted to neurological and neuropsychological assessment, neuro-ophthalmological tests, brain MRI, EEG and whole exome sequencing. A homozygous frameshift variant (NM_002087.4: c.768_769dup; p.Gln257Profs*27) was found. Distinct type descriptions, as in this case, increase the clinical spectrum of the disease.

Two-year follow-up of gait and postural control following initiation of recombinant human tripeptidyl intracerebroventricular enzyme replacement therapy in two atypical CLN2 patients

Neuronal ceroid lipofuscinosis type 2 (CLN2) is a rapidly progressive neurodegenerative disorder leading to premature mortality. Ambulatory CLN2 patients typically receive standard of care treatment through biweekly intracerebroventricular (ICV) enzyme replacement therapy (ERT) involving recombinant human tripeptidyl peptidase 1, known as cerliponase alfa (Brineura®, Biomarin Pharmaceuticals). This study longitudinally assessed the impact of ICV cerliponase alfa ERT on gait, and postural control across a two-year span in two siblings diagnosed with atypical CLN2 disease. Both participants, ID01 (18 years and 8 months old at enrollment) and ID02 (13 years and 3 months old at enrollment), exhibited symptomatic characteristics which were studied longitudinally over three years. Their evaluations assessed postural sway variability, potential for slips and trips, gait metrics, sit-to-stand durations, scores from the sensory organization test (SOT), and gross motor function measure (GMFM) scores. Findings indicated a decline in postural complexity and stability in the medial-lateral (ML) axis, a reduction in toe clearance, and an augmented risk of stumbling for the participants. Over the two-year period of ERT, both siblings exhibited a progressive decline in walking velocity, characterized by reductions in step length and prolonged gait cycle time. The elder sibling demonstrated a notable increase in double support duration, indicative of heightened reliance on proprioceptive input to maintain stability during ambulation. Additionally, sit-to-stand times lengthened for siblings, further reflecting declines in motor function. Despite these challenges, SOT scores showed improvement after two years of ERT, suggesting some preservation of sensory integration. These findings in SOT scores indicate that cerliponase alfa treatment in patients with atypical CLN2 disease may confer benefits in postural stability, lower extremity strength, and ankle stiffness. However, declines in more complex motor functions, including sit-to-stand performance and postural complexity, persist, underscoring the progressive nature of the disease despite ongoing therapeutic intervention.

Drug-refractory epilepsy due to a novel CLN5 mutation: A report of three patients from an Indian family

INTRODUCTION

Neuronal Ceroid Lipofuscinosis (NCL) are a group of lysosomal storage disorders characterised by progressive neurodegeneration caused by an accumulation of ceroid lipopigment in lysosomes of neurons and other cell types. Adult-onset NCL (Kufs disease) differs from childhood forms by its later onset and preserved vision. Type A (Kufs A) presents as progressive myoclonus epilepsy (PME), while Type B (Kufs B) manifests as dementia with motor involvement. Both subtypes have distinct causative genes.

METHODS

We have described 3 siblings with genetically confirmed novel pathogenic CLN5 subtype who presented with developmental regression, drug-refractory myoclonic epilepsy, and dementia (Kufs A).

RESULTS

We have presented 3 siblings with adult onset NCL with Kufs A (not Kufs B) phenotype, which has been rarely documented.

CONCLUSION

Genotypic-phenotypic variations are increasingly being reported for NCL. We have described three patients from a family with CLN5 subtype who had prominent drug refractory myoclonic epilepsy, which is extremely rare.

Adult-Onset Neuronal Ceroid Lipofuscinosis: CLN5 Variant Presenting as Focal Dystonia

Background

Neuronal ceroid lipofuscinosis (NCL) is a rare hereditary lysosomal storage disorder causing neuronal loss and progressive neurodegeneration. CLN variants cause varied phenotypic presentations.

Case report

A 49-year-old male presented with late adult-onset progressive focal right lower limb dystonia. Imaging showed cerebellar atrophy, and genetic testing was positive for the CLN5 variant (c.826T > C; p.Phe276 Leu) with uncertain significance. Skin biopsy suggested NCL, which made us consider the variant pathogenic, leading to novel phenotypic presentation.

Conclusion

Isolated focal dystonia has not been reported as an initial presentation in ANCL. Early genetic testing and periodic clinical assessments are advisable for better management and prognostication.

Neuroimaging Applications for the Delivery and Monitoring of Gene Therapy for Central Nervous System Diseases

Neurological disease due to single-gene defects represents a targetable entity for adeno-associated virus (AAV)-mediated gene therapy. The delivery of AAV-mediated gene therapy to the brain is challenging, owing to the presence of the blood-brain barrier. Techniques in gene transfer, such as convection-enhanced intraparenchymal delivery and image-guided delivery to the cerebrospinal fluid spaces of the brain, have led the field into highly accurate delivery techniques, which provide correction of genetic defects in specific brain regions or more broadly. These techniques commonly use magnetic resonance imaging (MRI), computed tomography, and fluoroscopic guidance. Even more, the neuroimaging changes evaluated by MRI, MR spectroscopy, diffusion tensor imaging, and functional MRI can serve as important biomarkers of therapy effect and overall disease progression. Here, we discuss the role of neuroimaging in delivering AAV vectors and monitoring the effect of gene therapy.

A novel pathogenic variant in the KCTD7 gene in a patient with neuronal ceroid lipofuscinosis (CLN14): a case report and review of the literature

BACKGROUND

Neuronal ceroid lipofuscinosis (NCL) is a heterogeneous group of 13 rare, progressive neurodegenerative diseases of the brain and retina. CLN14 is a very rare subtype of NCL caused by pathogenic variants in the KCTD7 gene. Only four cases of this subtype have been reported in the literature.

CASE PRESENTATION

A nine-month-old, previously healthy male who was firstborn to first-cousin parents presented with progressive psychomotor regression, dysmorphic facial features, myoclonus, and vision loss. Neurological examination showed generalized hypotonia and brisk reflexes. He continued to deteriorate until age 18 months, when he developed his first generalized tonic-clonic seizure. An ophthalmological examination showed a hypopigmented fundus and slight temporal disc pallor. Brain MRI showed mild generalized brain atrophy and white matter disease. EEG revealed a severely abnormal trace marked by generalized, high amplitude, sharply contoured, polymorphic delta slowing intermixed with theta slowing and some alpha activity, with disorganized and scattered spikes and sharp waves. The patient continued to have uncontrolled seizures and further psychomotor regression until he died of status epilepticus and pneumonia at the age of 44 months. WES identified a novel homozygous variant c.413T > C, p.(Leu138Pro) in the KCTD7 gene, causing an amino acid transition from leucine to proline at position 138. Both parents were carriers of the same variant.

CONCLUSIONS

We present the fifth known case of CLN14 in the literature and report the clinical course and a novel underlying likely causative variant in the KCTD7 gene. The improving accessibility and affordability of genetic testing will likely uncover more NCL cases and further expand the disease's genotypic and phenotypic spectrum.

Glucose metabolism impairment as a hallmark of progressive myoclonus epilepsies: a focus on neuronal ceroid lipofuscinoses

Glucose is the brain's main fuel source, used in both energy and molecular production. Impaired glucose metabolism is associated with adult and pediatric neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), GLUT1 deficiency syndrome, and progressive myoclonus epilepsies (PMEs). PMEs, a group of neurological disorders typical of childhood and adolescence, account for 1% of all epileptic diseases in this population worldwide. Diffuse glucose hypometabolism is observed in the brains of patients affected by PMEs such as Lafora disease (LD), dentatorubral-pallidoluysian (DRPLA) atrophy, Unverricht-Lundborg disease (ULD), and myoclonus epilepsy with ragged red fibers (MERRFs). PMEs also include neuronal ceroid lipofuscinoses (NCLs), a subgroup in which lysosomal and autophagy dysfunction leads to progressive loss of vision, brain atrophy, and cognitive decline. We examine the role of impaired glucose metabolism in neurodegenerative diseases, particularly in the NCLs. Our literature review, which includes findings from case reports and animal studies, reveals that glucose hypometabolism is still poorly characterized both in vitro and in vivo in the different NCLs. Better identification of the glucose metabolism pathway impaired in the NCLs may open new avenues for evaluating the therapeutic potential of anti-diabetic agents in this population and thus raise the prospect of a therapeutic approach able to delay or even halt disease progression.

An update on multiplexed mass spectrometry-based lysosomal storage disease diagnosis

Lysosomal storage disorders (LSDs) are a type of inherited metabolic disorders in which biomolecules, accumulate as a specific substrate in lysosomes due to specific individual enzyme deficiencies. Despite the fact that LSDs are incurable, various approaches, including enzyme replacement therapy, hematopoietic stem cell transplantation, or gene therapy are now available. Therefore, a timely diagnosis is a critical initial step in patient treatment. The-state-of-the-art in LSD diagnostic uses, in the first stage, enzymatic activity determination by fluorimetry or by mass spectrometry (MS) with the aid of dry blood spots, based on different enzymatic substrate structures. Due to its sensitivity, high precision, and ability to screen for an unprecedented number of diseases in a single assay, multiplexed tandem MS-based enzyme activity assays for the screening of LSDs in newborns have recently received a lot of attention. Here, (i) we review the current approaches used for simultaneous enzymatic activity determination of LSDs in dried blood spots using multiplex-LC-MS/MS; (ii) we explore the need for designing novel enzymatic substrates that generate different enzymatic products with distinct molecular masses in multiplexed-MS studies; and (iii) we give examples of the relevance of affinity-MS technique as a basis for reversing undesirable immune-reactivity in enzyme replacement therapy.

Pediatric onset neuronal ceroid lipofuscinoses: Unraveling clinical and genetic specifications

Objective

To unravel the clinical and genetic specifications of Neuronal ceroid lipofuscinosis (NCL).

Methods

This is a retrospective cross-sectional study conducted in the Department of Pediatric Neurology Children Hospital and University of Child Health Sciences, Lahore, Pakistan from March 2017 to March 2022. The primary outcome was to measure genotype-phenotype correlation by segregation of phenotypes according to genotype. The secondary outcomes included a correlation between genotype and distribution of age(s) of onset.

Results

One hundred fifty three patients clinically diagnosed with NCL underwent genetic testing and pathologic mutation was identified in 32.7% of patients. About 59.6% were male and 37.2% had an affected sibling. The median age was 5.46±1.95 years at the onset of the first symptom i.e., myoclonic seizures in 68%, and motor difficulty in 24%. Other features found were global developmental delay (56%), hypotonia (23%), visual impairment (80%), ataxia (22%), and disc pallor (56%). The most common type was CLN6 (Ceroid lipofuscinosis neuronal) (42%), CLN2 (16%) followed by CLN7 (12%). When 50 patients with recognized mutations were compared with 103 patients with no mutation, family history (p=0.049), early visual loss (p=0.016), hypotonia (p=0.001), white matter signals (p=0.026) and pan-atrophy(p=0.047) was statistically significant in the genetically confirmed NCL. Multiple pairwise comparisons indicated that the estimated age of onset for the CLN1 and CLN2 mutation group was significantly lower than other genotypes including CLN6 (p 0.012), CLN10 (p 0.007) and CLN12 (p 0.007).

Conclusion

Following a detailed review of NCL symptomatology, a clinically-oriented approach should be used for a rapid diagnosis with confirmation by targeted molecular testing for future genetic counseling.

Neuronal ceroid lipofuscinosis in a Schapendoes dog is caused by a missense variant in CLN6

Neuronal ceroid lipofuscinosis (NCL) is a group of neurodegenerative disorders that occur in humans, dogs, and several other species. NCL is characterised clinically by progressive deterioration of cognitive and motor function, epileptic seizures, and visual impairment. Most forms present early in life and eventually lead to premature death. Typical pathological changes include neuronal accumulation of autofluorescent, periodic acid-Schiff- and Sudan black B-positive lipopigments, as well as marked loss of neurons in the central nervous system. Here, we describe a 19-month-old Schapendoes dog, where clinical signs were indicative of lysosomal storage disease, which was corroborated by pathological findings consistent with NCL. Whole genome sequencing of the affected dog and both parents, followed by variant calling and visual inspection of known NCL genes, identified a missense variant in CLN6 (c.386T>C). The variant is located in a highly conserved region of the gene and predicted to be harmful, which supports a causal relationship. The identification of this novel CLN6 variant enables pre-breeding DNA-testing to prevent future cases of NCL6 in the Schapendoes breed, and presents a potential natural model for NCL6 in humans.

Loss of the lysosomal protein CLN3 modifies the lipid content of the nuclear envelope leading to DNA damage and activation of YAP1 pro-apoptotic signaling

Batten disease is characterized by early-onset blindness, juvenile dementia and death during the second decade of life. The most common genetic causes are mutations in the CLN3 gene encoding a lysosomal protein. There are currently no therapies targeting the progression of the disease, mostly due to the lack of knowledge about the disease mechanisms. To gain insight into the impact of CLN3 loss on cellular signaling and organelle function, we generated CLN3 knock-out cells in a human cell line (CLN3-KO), and performed RNA sequencing to obtain the cellular transcriptome. Following a multi-dimensional transcriptome analysis, we identified the transcriptional regulator YAP1 as a major driver of the transcriptional changes observed in CLN3-KO cells. We further observed that YAP1 pro-apoptotic signaling is hyperactive as a consequence of CLN3 functional loss in retinal pigment epithelia cells, and in the hippocampus and thalamus of CLN3exΔ7/8 mice, an established model of Batten disease. Loss of CLN3 activates YAP1 by a cascade of events that starts with the inability of releasing glycerophosphodiesthers from CLN3-KO lysosomes, which leads to perturbations in the lipid content of the nuclear envelope and nuclear dysmorphism. This results in increased number of DNA lesions, activating the kinase c-Abl, which phosphorylates YAP1, stimulating its pro-apoptotic signaling. Altogether, our results highlight a novel organelle crosstalk paradigm in which lysosomal metabolites regulate nuclear envelope content, nuclear shape and DNA homeostasis. This novel molecular mechanism underlying the loss of CLN3 in mammalian cells and tissues may open new c-Abl-centric therapeutic strategies to target Batten disease.

Two compound heterozygous variants in the CLN8 gene are responsible for neuronal cereidolipofuscinoses disorder in a child: a case report

Background

Neuronal Ceroid Lipofuscinosis (NCL) disorders, recognized as the primary cause of childhood dementia globally, constitute a spectrum of genetic abnormalities. CLN8, a subtype within NCL, is characterized by cognitive decline, motor impairment, and visual deterioration. This study focuses on an atypical case with congenital onset and a remarkably slow disease progression.

Methods

Whole-genome sequencing at 30× coverage was employed as part of a national genomics program to investigate the genetic underpinnings of rare diseases. This genomic approach aimed to challenge established classifications (vLINCL and EPMR) and explore the presence of a continuous phenotypic spectrum associated with CLN8.

Results

The whole-genome sequencing revealed two novel likely pathogenic mutations in the CLN8 gene on chromosome 8p23.3. These mutations were not previously associated with CLN8-related NCL. Contrary to established classifications (vLINCL and EPMR), our findings suggest a continuous phenotypic spectrum associated with CLN8. Pathological subcellular markers further validated the genomic insights.

Discussion

The identification of two previously undescribed likely pathogenic CLN8 gene mutations challenges traditional classifications and highlights a more nuanced phenotypic spectrum associated with CLN8. Our findings underscore the significance of genetic modifiers and interactions with unrelated genes in shaping variable phenotypic outcomes. The inclusion of pathological subcellular markers further strengthens the validity of our genomic insights. This research enhances our understanding of CLN8 disorders, emphasizing the need for comprehensive genomic analyses to elucidate the complexity of phenotypic presentations and guide tailored therapeutic strategies. The identification of new likely pathogenic mutations underscores the dynamic nature of CLN8-related NCL and the importance of individualized approaches to patient management.

Recognizing Lipofuscinosis as a Guide in Antiepileptic Treatment: Clinical Description of the First Mexican Case With Neuronal Ceroid Lipofuscinosis Type 7 (NCL7)

Neuronal ceroid lipofuscinosis type 7 (NCL7) is a rare form of childhood dementia; it is part of a group of diseases characterized by rapid progressive cognitive decline, blindness associated with retinitis pigmentosa, and seizures. We report the clinical and molecular characteristics of the first Mexican patient with NCL7, highlighting a particularly atypical disease course. The typical presentation form is expected to have reduced life expectancy and an average age of ambulation loss at 12 years. Our 27-year-old patient retains the ability to walk. The patient's unique presentation could, in part, be attributed to her genetic profile: a hypomorphic allele carrying a missense variant (c.1390G>A) and an almost null allele with a frameshift variant (c.1086del), contributing to the preservation of some protein function. Throughout her childhood and early adulthood, our patient experienced a variable response to antiseizure drugs, attributed to a lack of recognition of the disease and the specific efficacy of certain antiseizure medications. Our findings underscore the significance of considering this genetic condition and acknowledging its clinical heterogeneity.

Classic and Atypical Late Infantile Neuronal Ceroid Lipofuscinosis in Latin America: Clinical and Genetic Aspects, and Treatment Outcome with Cerliponase Alfa

Introduction

Late infantile neuronal ceroid lipofuscinosis type 2 (CLN2), is a neurodegenerative autosomal recessive disease caused by TPP1 gene variants, with a spectrum of classic and atypical phenotypes. The aim of treatment is to slow functional decline as early as possible in an attempt to improve quality of life and survival. This study describes the clinical characteristics as well as the response to treatment with cerliponase alfa.

Materials and methods

A retrospective study was conducted in five Latin-American countries, using clinical records from patients with CLN2. Clinical follow-up and treatment variables are described. A descriptive and bivariate statistical analysis was performed.

Results

A total of 36 patients were observed (range of follow-up of 61-110 weeks post-treatment). At presentation, patients with the classic phenotype (n = 16) exhibited regression in language (90%), while seizures were the predominant symptom (87%) in patients with the atypical phenotype (n = 20). Median age of symptom onset and time to first specialized consultation was 3 (classical) and 7 (atypical) years, while the median time interval between onset of symptoms and treatment initiation was 4 years (classical) and 7.5 (atypical). The most frequent variant was c.827 A > T in 17/72 alleles, followed by c.622C > T in 6/72 alleles. All patients were treated with cerliponase alfa, and either remained functionally stable or had a loss of 1 point on the CLN2 scale, or up to 2 points on the Wells Cornel and Hamburg scales, when compared to pretreatment values.

Discussion and conclusion

This study reports the largest number of patients with CLN2 currently on treatment with cerliponase alfa in the world. Data show a higher frequency of patients with atypical phenotypes and a high allelic proportion of intron variants in our region. There was evidence of long intervals until first specialized consultation, diagnosis, and enzyme replacement therapy. Follow-up after the initiation of cerliponase alfa showed slower progression or stabilization of the disease, associated with adequate clinical outcomes and stable functional scores. These improvements were consistent in both clinical phenotypes.

Comparative Hippocampal Proteome and Phosphoproteome in a Niemann-Pick, Type C1 Mouse Model Reveal Insights into Disease Mechanisms

Niemann-Pick disease, type C (NPC) is a neurodegenerative, lysosomal storage disorder in individuals carrying two mutated copies of either the NPC1 or NPC2 gene. Consequently, impaired cholesterol recycling and an array of downstream events occur. Interestingly, in NPC, the hippocampus displays lysosomal lipid storage but does not succumb to progressive neurodegeneration as significantly as other brain regions. Since defining the neurodegeneration mechanisms in this disease is still an active area of research, we use mass spectrometry to analyze the overall proteome and phosphorylation pattern changes in the hippocampal region of a murine model of NPC. Using 3 week old mice representing an early disease time point, we observed changes in the expression of 47 proteins, many of which are consistent with the previous literature. New to this study, changes in members of the SNARE complex, including STX7, VTI1B, and VAMP7, were identified. Furthermore, we identified that phosphorylation of T286 on CaMKIIα and S1303 on NR2B increased in mutant animals, even at the late stage of the disease. These phosphosites are crucial to learning and memory and can trigger neuronal death by altering protein-protein interactions.

Dem-Aging: autophagy-related pathologies and the "two faces of dementia"

Neuronal ceroid lipofuscinosis (NCL) is an umbrella term referring to the most frequent childhood-onset neurodegenerative diseases, which are also the main cause of childhood dementia. Although the molecular mechanisms underlying the NCLs remain elusive, evidence is increasingly pointing to shared disease pathways and common clinical features across the disease forms. The characterization of pathological mechanisms, disease modifiers, and biomarkers might facilitate the development of treatment strategies.The DEM-AGING project aims to define molecular signatures in NCL and expedite biomarker discovery with a view to identifying novel targets for monitoring disease status and progression and accelerating clinical trial readiness in this field. In this study, we fused multiomic assessments in established NCL models with similar data on the more common late-onset neurodegenerative conditions in order to test the hypothesis of shared molecular fingerprints critical to the underlying pathological mechanisms. Our aim, ultimately, is to combine data analysis, cell models, and omic strategies in an effort to trace new routes to therapies that might readily be applied in the most common forms of dementia.

Lipofuscin, Its Origin, Properties, and Contribution to Retinal Fluorescence as a Potential Biomarker of Oxidative Damage to the Retina

Lipofuscin accumulates with age as intracellular fluorescent granules originating from incomplete lysosomal digestion of phagocytosed and autophagocytosed material. The purpose of this review is to provide an update on the current understanding of the role of oxidative stress and/or lysosomal dysfunction in lipofuscin accumulation and its consequences, particularly for retinal pigment epithelium (RPE). Next, the fluorescence of lipofuscin, spectral changes induced by oxidation, and its contribution to retinal fluorescence are discussed. This is followed by reviewing recent developments in fluorescence imaging of the retina and the current evidence on the prognostic value of retinal fluorescence for the progression of age-related macular degeneration (AMD), the major blinding disease affecting elderly people in developed countries. The evidence of lipofuscin oxidation in vivo and the evidence of increased oxidative damage in AMD retina ex vivo lead to the conclusion that imaging of spectral characteristics of lipofuscin fluorescence may serve as a useful biomarker of oxidative damage, which can be helpful in assessing the efficacy of potential antioxidant therapies in retinal degenerations associated with accumulation of lipofuscin and increased oxidative stress. Finally, amendments to currently used fluorescence imaging instruments are suggested to be more sensitive and specific for imaging spectral characteristics of lipofuscin fluorescence.

Integrative human and murine multi-omics: Highlighting shared biomarkers in the neuronal ceroid lipofuscinoses

Neuronal ceroid lipofuscinosis (NCL) is a group of neurodegenerative disorders whose molecular mechanisms remain largely unknown. Omics approaches are among the methods that generate new information on modifying factors and molecular signatures. Moreover, omics data integration can address the need to progressively expand knowledge around the disease and pinpoint specific proteins to promote as candidate biomarkers. In this work, we integrated a total of 62 proteomic and transcriptomic datasets originating from humans and mice, employing a new approach able to define dysregulated processes across species, stages and NCL forms. Moreover, we selected a pool of differentially expressed proteins and genes as species- and form-related biomarkers of disease status/progression and evaluated local and spatial differences in most affected brain regions. Our results offer promising targets for potential new therapeutic strategies and reinforce the hypothesis of a connection between NCLs and other forms of dementia, particularly Alzheimer's disease.

The involvement of Purkinje cells in progressive myoclonic epilepsy: Focus on neuronal ceroid lipofuscinosis

The progressive myoclonic epilepsies (PMEs) are a group of rare neurodegenerative diseases characterized by myoclonus, epileptic seizures, and progressive neurological deterioration with cerebellar involvement. They include storage diseases like Gaucher disease, Lafora disease, and forms of neuronal ceroid lipofuscinosis (NCL). To date, 13 NCLs have been reported (CLN1-CLN8, CLN10-CLN14), associated with mutations in different genes. These forms, which affect both children and adults, are characterized by seizures, cognitive and motor impairments, and in most cases visual loss. In NCLs, as in other PMEs, central nervous system (CNS) neurodegeneration is widespread and involves different subpopulations of neurons. One of the most affected regions is the cerebellar cortex, where motor and non-motor information is processed and transmitted to deep cerebellar nuclei through the axons of Purkinje cells (PCs). PCs, being GABAergic, have an inhibitory effect on their target neurons, and provide the only inhibitory output of the cerebellum. Degeneration of PCs has been linked to motor impairments and epileptic seizures. Seizures occur when some insult upsets the normal balance in the CNS between excitatory and inhibitory impulses, causing hyperexcitability. Here we review the role of PCs in epilepsy onset and progression following their PME-related loss. In particular, we focus on the involvement of PCs in seizure phenotype in NCLs, highlighting findings from case reports and studies of animal models in which epilepsy can be linked to PC loss.

Clinical and genetic characterization of neuronal ceroid lipofuscinoses (NCLs) in 29 Iranian patients: identification of 11 novel mutations

Neuronal ceroid lipofuscinoses (NCLs) are neurodegenerative lysosomal storage diseases which are considered among the most frequent causes of dementia in childhood worldwide This study aimed to identify the gene variants, molecular etiologies, and clinical features in 23 unrelated Iranian families with NCL. In total, 29 patients with neuronal ceroid lipofuscinoses (NCLs), diagnosed based on clinical manifestations, MRI neuroimaging, and electroencephalography (EEG), were recruited for this study. Through whole-exome sequencing (WES), functional prediction, Sanger sequencing, and segregation analysis, we found that 12 patients (41.3%) with mutations in the CLN6 gene, 7 patients (24%) with the TPP1 (CLN2) gene variants, and 4 patients (13.7%) with mutations in the MFSD8 (CLN7) gene. Also, mutations in each of the CLN3 and CLN5 genes were detected in 2 cases and mutations of each PPT1 (CLN1) and CLN8 gene were observed in only 1 separate patient. We identified 18 different mutations, 11 (61%) of which are novel, never have been reported before, and the others have been previously described. The gene variants identified in this study expand the number of published clinical cases and the variant frequency spectrum of the neuronal ceroid lipofuscinoses (NCLs) genes; moreover, the identification of these variants supplies foundational clues for future NCL diagnosis and therapy.

Building better brains: the pleiotropic function of neurotrophic factors in postnatal cerebellar development

The cerebellum is a multifunctional brain region that controls diverse motor and non-motor behaviors. As a result, impairments in the cerebellar architecture and circuitry lead to a vast array of neuropsychiatric and neurodevelopmental disorders. Neurotrophins and neurotrophic growth factors play essential roles in the development as well as maintenance of the central and peripheral nervous system which is crucial for normal brain function. Their timely expression throughout embryonic and postnatal stages is important for promoting growth and survival of both neurons and glial cells. During postnatal development, the cerebellum undergoes changes in its cellular organization, which is regulated by a variety of molecular factors, including neurotrophic factors. Studies have shown that these factors and their receptors promote proper formation of the cerebellar cytoarchitecture as well as maintenance of the cerebellar circuits. In this review, we will summarize what is known on the neurotrophic factors' role in cerebellar postnatal development and how their dysregulation assists in developing various neurological disorders. Understanding the expression patterns and signaling mechanisms of these factors and their receptors is crucial for elucidating their function within the cerebellum and for developing therapeutic strategies for cerebellar-related disorders.

Batten disease through different in vivo and in vitro models: A review

Batten disease consists of a family of primarily autosomal recessive, progressive neuropediatric disorders, also known as neuronal ceroid lipofuscinoses (NCLs). These pathologies are characterized by seizures and visual, cognitive and motor decline, and premature death. The pathophysiology of this rare disease is still unclear despite the years of trials and financial aids. This paper has reviewed advantages and limits of in vivo and in vitro models of Batten disease from murine and larger animal models to primitive unicellular models, until the most recently developed patient-derived induced pluripotent stem cells. For each model advantages, limits and applications were analyzed. The first prototypes investigated were murine models that due to their limits were replaced by larger animals. In vitro models gradually replaced animal models for practical, cost, and ethical reasons. Using induced pluripotent stem cells to study neurodegeneration is a new way of studying the disease, since they can be distinguished into differentiating elements like neurons, which are susceptible to neurodegeneration. In vivo and in vitro models have contributed to clarifying to some extent the pathophysiology of the disease. The collection and sharing of suitable human bio samples likely through biobanks can contribute to a better understanding, prevention, and to identify possible treatment strategies of Batten disease.

Lipidomics-Paving the Road towards Better Insight and Precision Medicine in Rare Metabolic Diseases

Even though the application of Next-Generation Sequencing (NGS) has significantly facilitated the identification of disease-associated mutations, the diagnostic rate of rare diseases is still below 50%. This causes a diagnostic odyssey and prevents specific treatment, as well as genetic counseling for further family planning. Increasing the diagnostic rate and reducing the time to diagnosis in children with unclear disease are crucial for a better patient outcome and improvement of quality of life. In many cases, NGS reveals variants of unknown significance (VUS) that need further investigations. The delineation of novel (lipid) biomarkers is not only crucial to prove the pathogenicity of VUS, but provides surrogate parameters for the monitoring of disease progression and therapeutic interventions. Lipids are essential organic compounds in living organisms, serving as building blocks for cellular membranes, energy storage and signaling molecules. Among other disorders, an imbalance in lipid homeostasis can lead to chronic inflammation, vascular dysfunction and neurodegenerative diseases. Therefore, analyzing lipids in biological samples provides great insight into the underlying functional role of lipids in healthy and disease statuses. The method of choice for lipid analysis and/or huge assemblies of lipids (=lipidome) is mass spectrometry due to its high sensitivity and specificity. Due to the inherent chemical complexity of the lipidome and the consequent challenges associated with analyzing it, progress in the field of lipidomics has lagged behind other omics disciplines. However, compared to the previous decade, the output of publications on lipidomics has increased more than 17-fold within the last decade and has, therefore, become one of the fastest-growing research fields. Combining multiple omics approaches will provide a unique and efficient tool for determining pathogenicity of VUS at the functional level, and thereby identifying rare, as well as novel, genetic disorders by molecular techniques and biochemical analyses.

Whole exome screening of neurodevelopmental regression disorders in a cohort of Egyptian patients

Developmental regression describes a child who begins to lose his previously acquired milestones skills after he has reached a certain developmental stage and though affects his childhood development. It is associated with neurodegenerative diseases including leukodystrophy and neuronal ceroid lipofuscinosis diseases (NCLs), one of the most frequent childhood-onset neurodegenerative disorders. The current study focused on screening causative genes of developmental regression diseases comprising neurodegenerative disorders in Egyptian patients using next-generation sequencing (NGS)-based analyses as well as developing checklist to support clinicians who are not familiar with these diseases. A total of 763 Egyptian children (1 to 11 years), mainly diagnosed with developmental regression, seizures, or visual impairment, were studied using whole exome sequencing (WES). Among 763 Egyptian children, 726 cases were early clinically and molecularly diagnosed, including 482 cases that had pediatric stroke, congenital infection, and hepatic encephalopathy; meanwhile, 192 had clearly dysmorphic features, 31 showed central nervous system (CNS) malformation, 17 were diagnosed by leukodystrophy, 2 had ataxia telangiectasia, and 2 were diagnosed with tuberous sclerosis. The remained 37 out of 763 candidates were suspected with NCLs symptoms; however, 28 were confirmed to be NCLs patients, 1 was Kaya-Barakat-Masson syndrome, 1 was diagnosed as infantile neuroaxonal dystrophy, and 7 cases required further molecular diagnosis. This study provided an NGS-based approach of the genetic causes of developmental regression and neurodegenerative diseases as it comprised different variants and de novo mutations with complex phenotypes of these diseases which in turn help in early diagnoses and counseling for affected families.

From amaurotic idiocy to biochemically defined lipid storage diseases: the first identification of GM1-Gangliosidosis

On February 23rd 1936, a boy-child ("Kn") died in an asylum near Munich after years of severe congenital disease, which had profoundly impaired his development leading to inability to walk, talk and see as well as to severe epilepsy. While a diagnosis of "Little's disease" was made during life, his postmortem brain investigation at Munich neuropathology ("Deutsche Forschungsanstalt für Psychiatrie") revealed the diagnosis of "amaurotic idiocy" (AI). AI, as exemplified by Tay-Sachs-Disease (TSD), back then was not yet understood as a specific inborn error of metabolism encompassing several disease entities. Many neuropathological studies were performed on AI, but the underlying processes could only be revealed by new scientific techniques such as biochemical analysis of nervous tissue, deciphering AI as nervous system lipid storage diseases, e.g. GM2-gangliosidosis. In 1963, Sandhoff & Jatzkewitz published an article on a "biochemically special form of AI" reporting striking differences when comparing their biochemical observations of hallmark features of TSD to tissue composition in a single case: the boy Kn. This was the first description of "GM1-Gangliosidosis", later understood as resulting from genetically determined deficiency in beta-galactosidase. Here we present illustrative materials from this historic patient, including selected diagnostic slides from the case "Kn" in virtual microscopy, original records and other illustrative material available. Finally, we present results from genetic analysis performed on archived tissue proving beta-galactosidase-gene mutation, verifying the 1963 interpretation as correct. This synopsis shall give a first-hand impression of this milestone finding in neuropathology. Original paper: On a biochemically special form of infantile amaurotic idiocy. Jatzkewitz H., Sandhoff K., Biochim. Biophys. Acta 1963; 70; 354-356. See supplement 1.

Neuronal ceroid lipofuscinosis in the South American-Caribbean region: An epidemiological overview

Neuronal ceroid lipofuscinoses (NCLs) comprise 13 hereditary neurodegenerative pathologies of very low frequency that affect individuals of all ages around the world. All NCLs share a set of symptoms that are similar to other diseases. The exhaustive collection of data from diverse sources (clinical, genetic, neurology, ophthalmology, etc.) would allow being able in the future to define this group with greater precision for a more efficient diagnostic and therapeutic approach. Despite the large amount of information worldwide, a detailed study of the characteristics of the NCLs in South America and the Caribbean region (SA&C) has not yet been done. Here, we aim to present and analyse the multidisciplinary evidence from all the SA&C with qualitative weighting and biostatistical evaluation of the casuistry. Seventy-one publications from seven countries were reviewed, and data from 261 individuals (including 44 individuals from the Cordoba cohort) were collected. Each NCL disease, as well as phenotypical and genetic data were described and discussed in the whole group. The CLN2, CLN6, and CLN3 disorders are the most frequent in the region. Eighty-seven percent of the individuals were 10 years old or less at the onset of symptoms. Seizures were the most common symptom, both at onset (51%) and throughout the disease course, followed by language (16%), motor (15%), and visual impairments (11%). Although symptoms were similar in all NCLs, some chronological differences could be observed. Sixty DNA variants were described, ranging from single nucleotide variants to large chromosomal deletions. The diagnostic odyssey was probably substantially decreased after medical education activities promoted by the pharmaceutical industry and parent organizations in some SA&C countries. There is a statistical deviation in the data probably due to the approval of the enzyme replacement therapy for CLN2 disease, which has led to a greater interest among the medical community for the early description of this pathology. As a general conclusion, it became clear in this work that the combined bibliographical/retrospective evaluation approach allowed a general overview of the multidisciplinary components and the epidemiological tendencies of NCLs in the SA&C region.

Recent Insight into the Genetic Basis, Clinical Features, and Diagnostic Methods for Neuronal Ceroid Lipofuscinosis

Neuronal ceroid lipofuscinoses (NCLs) are a group of rare, inherited, neurodegenerative lysosomal storage disorders that affect children and adults. They are traditionally grouped together, based on shared clinical symptoms and pathological ground. To date, 13 autosomal recessive gene variants, as well as one autosomal dominant gene variant, of NCL have been described. These genes encode a variety of proteins, whose functions have not been fully defined; most are lysosomal enzymes, transmembrane proteins of the lysosome, or other organelles. Common symptoms of NCLs include the progressive loss of vision, mental and motor deterioration, epileptic seizures, premature death, and, in rare adult-onset cases, dementia. Depending on the mutation, these symptoms can vary, with respect to the severity and onset of symptoms by age. Currently, all forms of NCL are fatal, and no curative treatments are available. Herein, we provide an overview to summarize the current knowledge regarding the pathophysiology, genetics, and clinical manifestation of these conditions, as well as the approach to diagnosis.