Neuronal ceroid lipofuscinosis: genetic and phenotypic spectrum of 14 patients from Turkey

Clinical and Molecular Characteristics of Neuronal Ceroid Lipofuscinosis in Saudi Arabia

BACKGROUND

Neuronal ceroid lipofuscinoses (NCLs) represent a heterogeneous group of inherited metabolic lysosomal disorders characterized by neurodegeneration. This study sought to describe the clinical and molecular characteristics of NCLs in Saudi Arabia and determine the most common types in that population.

METHODS

A retrospective review of electronic medical records was conducted for 63 patients with NCL (55 families) from six tertiary and referral centers in Saudi Arabia between 2008 and 2022. Clinical, radiological, and neurophysiological data as well as genetic diagnoses were reviewed.

RESULTS

CLN6 was the predominant type, accounting for 45% of cases in 25 families. The most common initial symptoms were speech delay (53%), cognitive decline (50%) and/or gait abnormalities (48%), and seizure (40%). Behavioral symptomatology was observed in 20%, whereas visual impairment was less frequently (9.3%) encountered. Diffuse cerebral and cerebellar atrophy was the predominant finding on brain magnetic resonance imaging. Electroencephalography generally revealed background slowing in all patients with generalized epileptiform discharges in 60%. The most common genotype detected was the p.Ser265del variant found in 36% (20 of 55 families). The most rapidly progressive subtypes were CLN2 and CLN6. Two patients with each died at age five years. The earliest age at which a patient was nonambulatory was two years in a patient with CLN14.

CONCLUSIONS

This is the largest molecularly confirmed NCL cohort study from Saudi Arabia. Characterizing the natural history of specific NLC types can increase understanding of the underlying pathophysiology and distinctive genotype-phenotype characteristics, facilitating early diagnosis and treatment initiation as well as genetic counseling for families.

Neuronal ceroid lipofuscinosis type 11 diagnosed patient with bi-allelic variants in GRN gene: case report and review of literature

OBJECTIVES

Neuronal ceroid lipofuscinosis type 11 (NCL11) is a rare disease that presents with progressive cognitive decline, epilepsy, visual impairment, retinal atrophy, cerebellar ataxia and cerebellar atrophy. We present herein a case of NCL11 in a patient diagnosed with neuromotor developmental delay, epilepsy, bronchiolitis obliterans and hypothyroidism.

CASE PRESENTATION

A 4-year-old male patient was admitted to our clinic with global developmental delay and a medical history that included recurrent hospitalizations for pneumonia at the age of 17 days, and in months 4, 5 and 7. Family history revealed a brother with similar clinical findings (recurrent pneumonia, hypothyroidism, hypotonicity, swallowing dysfunction and neuromotor delay) who died from pneumonia at the age of 22 months. Computed tomography of the thorax was consistent with bronchiolitis obliterans, while epileptic discharges were identified on electroencephalogram with a high incidence of bilateral fronto-centro-temporal and generalized spike-wave activity but no photoparoxysmal response. Cranial MRI revealed T2 hyperintense areas in the occipital periventricular white matter and volume loss in the white matter, a thin corpus callosum and vermis atrophy. A whole-exome sequencing molecular analysis revealed compound heterozygous c.430G>A (p.Asp144Asn) and c.415T>C (p.Cys139Arg) variants in the GRN gene.

CONCLUSIONS

The presented case indicates that NCL11 should be taken into account in patients with epilepsy and neurodegenerative diseases.

Linear Diagnostic Procedure Elicited by Clinical Genetics and Validated by mRNA Analysis in Neuronal Ceroid Lipofuscinosis 7 Associated with a Novel Non-Canonical Splice Site Variant in MFSD8

Neuronal ceroid lipofuscinoses (CNL) are lysosomal storage diseases that represent the most common cause of dementia in children. To date, 13 autosomal recessive (AR) and 1 autosomal dominant (AD) gene have been characterized. Biallelic variants in MFSD8 cause CLN7 type, with nearly 50 pathogenic variants, mainly truncating and missense, reported so far. Splice site variants require functional validation. We detected a novel homozygous non-canonical splice-site variant in MFSD8 in a 5-year-old girl who presented with progressive neurocognitive impairment and microcephaly. The diagnostic procedure was elicited by clinical genetics first, and then confirmed by cDNA sequencing and brain imaging. Inferred by the common geographic origin of the parents, an autosomal recessive inheritance was hypothesized, and SNP-array was performed as the first-line genetic test. Only three AR genes lying within the observed 24 Mb regions of homozygosity were consistent with the clinical phenotype, including EXOSC9, SPATA5 and MFSD8. The cerebral and cerebellar atrophy detected in the meantime by MRI, along with the suspicion of accumulation of ceroid lipopigment in neurons, prompted us to perform targeted MFSD8 sequencing. Following the detection of a splice site variant of uncertain significance, skipping of exon 8 was demonstrated by cDNA sequencing, and the variant was redefined as pathogenic.

CLN8 Mutations Presenting with a Phenotypic Continuum of Neuronal Ceroid Lipofuscinosis-Literature Review and Case Report

CLN8 is a ubiquitously expressed membrane-spanning protein that localizes primarily in the ER, with partial localization in the ER-Golgi intermediate compartment. Mutations in CLN8 cause late-infantile neuronal ceroid lipofuscinosis (LINCL). We describe a female pediatric patient with LINCL. She exhibited a typical phenotype associated with LINCL, except she did not present spontaneous myoclonus, her symptoms occurrence was slower and developed focal sensory visual seizures. In addition, whole-exome sequencing identified a novel homozygous variant in CLN8, c.531G>T, resulting in p.Trp177Cys. Ultrastructural examination featured abundant lipofuscin deposits within mucosal cells, macrophages, and monocytes. We report a novel CLN8 mutation as a cause for NCL8 in a girl with developmental delay and epilepsy, cerebellar syndrome, visual loss, and progressive cognitive and motor regression. This case, together with an analysis of the available literature, emphasizes the existence of a continuous spectrum of CLN8-associated phenotypes rather than a sharp distinction between them.