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.

"Atypical" Phenotypes of Neuronal Ceroid Lipofuscinosis: The Argentine Experience in the Genomic Era

ABSTRACT Neuronal Ceroid Lipofuscinosis (NCL) refers to a group of inherited lysosomal storage disorders characterized by the intracellular accumulation of ceroid-lipofuscin compounds and neurodegeneration. Fourteen genes are currently recognized with disease-causing DNA variants: PPT1/CLN1, TPP1/CLN2, CLN3, DNAJC5/CLN4, CLN5, CLN6, MFSD8/CLN7, CLN8, CTSD/CN10, GRN/CLN11, ATP13A2/CLN12, CTSF/CLN13, KCTD7/CLN14, TBCK/CLN15. In the frame of the Cordoba cohort, we studied N=51 cases. The aim of this paper is the observational and retrospective analysis of the "atypical" phenotypes. PCR-Sanger sequencing and/or massive exome sequencing were used as a screening methodology. One CLN1 subject showed an atypical prolonged (P) phenotype with null PPT1 activity and a heterozygous compound genotype: E5 c.451C>T, p.Arg151*/g.6302T>G (I3 c.363-3T>G). Other 11 CLN2 individuals (except one girl) showed TPP1 activity decreased to around 10% of the minimum value of the reference interval in leukocytes and saliva. The DNA variants E7 c.827A>T, p.Asp276Val and I7 c.887-10A>G were the most prevalent. One CLN8 individual showed an atypical congenital phenotype with a heterozygous combination of DNA variants: E2 c.1A>G, p.?/E3 c.792C>G, p.Asn264Lys. Massive sequencing was installed as a screening methodology for the precision diagnosis of atypical CLN1, CLN2, and CLN8 phenotypes. A genetic/phenotypic local registry is under construction.

The neuronal ceroid lipofuscinoses program: A translational research experience in Argentina.

BACKGROUND: The Argentinean program was initiated more than a decade ago as the first experience of systematic translational research focused on NCL in Latin America. The aim was to overcome misdiagnoses and underdiagnoses in the region. SUBJECTS: 216 NCL suspected individuals from 8 different countries and their direct family members. METHODS: Clinical assessment, enzyme testing, electron microscopy, and DNA screening. RESULTS AND DISCUSSION: 1) The study confirmed NCL disease in 122 subjects. Phenotypic studies comprised epileptic seizures and movement disorders, ophthalmology, neurophysiology, image analysis, rating scales, enzyme testing, and electron microscopy, carried out under a consensus algorithm; 2) DNA screening and validation of mutations in genes PPT1 (CLN1), TPP1 (CLN2), CLN3, CLN5, CLN6, MFSD8 (CLN7), and CLN8: characterization of variant types, novel/known mutations and polymorphisms; 3) Progress of the epidemiological picture in Latin America; and 4) NCL-like pathology studies in progress. The Translational Research Program was highly efficient in addressing the misdiagnosis/underdiagnosis in the NCL disorders. The study of "orphan diseases" in a public administrated hospital should be adopted by the health systems, as it positively impacts upon the family's quality of life, the collection of epidemiological data, and triggers research advances. This article is part of a Special Issue entitled: "Current Research on the Neuronal Ceroid Lipofuscinoses (Batten Disease)".

Neuronal ceroid lipofuscinosis type CLN2: a new rationale for the construction of phenotypic subgroups based on a survey of 25 cases in South America.

Tripeptidyl-peptidase 1 (TPP1) null or residual activity occurs in neuronal ceroid lipofuscinosis (NCL) with underlying TPP1/CLN2 mutations. A survey of 25 South American CLN2 affected individuals enabled the differentiation of two phenotypes: classical late-infantile and variant juvenile, each in approximately 50% of patients, with residual TPP1 activity occurring in approximately 32%. Each individual was assigned to one of three subgroups: (I) n=11, null TPP1 activity in leukocytes; (II) n=8, residual TPP1 activity of 0.60-15.85 nmol/h/mg (nr 110-476); (III) n=6, activity not measured in leukocytes. Curvilinear bodies (CB) appeared in almost all studied CLN2 subjects; the only exceptions occurred in cases of subgroup II: two individuals had combined CBs/fingerprints (FPs), and one case had pure FPs. There were 15 mutations (4 first published in this paper, 3 previously observed in South America by our group, and 8 previously observed by others). In subgroup I, mutations were either missense or nonsense; in subgroups II and III, mutations prevailed at the non-conserved intronic site, c.887-10A>G (intron 7), and to a lesser extent at c.89+5G>C (intron 2), in heterozygous combinations. Grouping phenotypically and genetically known individuals on the basis of TPP1 activity supported the concept that residual enzyme activity underlies a protracted disease course. The prevalence of intronic mutations at non-conserved sites in subgroup II individuals indicates that some alternative splicing might allow some residual TPP1 activity.