Aim Neuronal ceroid lipofuscinosis type 2 (CLN2) disease is an autosomal recessive inherited neurodegenerative lysosomal storage disorder caused by deficient tripeptidyl peptidase 1 (TPP1) enzyme, leading to progressive deterioration of neurological functions commonly occurring in children aged 2–4 years and culminating in early death. Atypical cases associated with earlier or later symptom onset, or even protracted course, have already been reported. Such variable manifestations may constitute an additional challenge to early diagnosis and initiation of appropriate treatment. The present work aimed to analyse clinical data from a cohort of Latin American CLN2 patients with atypical phenotypes. Methods Experts in inborn errors of metabolism from Latin America selected patients from their centres who were deemed by the clinicians to have atypical forms of CLN2, according to the current literature on this topic and their practical experience. Clinical and genetic data from the medical records were retrospectively revised. All cases were presented and analysed by these experts at an Advisory Board Meeting in São Paulo, Brazil, in October 2018. Results Seizures, language abnormalities and behavioural disorders were found as the first manifestations, appearing at the median age of 6 years, an older age than classically described for the late infantile form. Three novel mutations were also identified. Conclusion Our findings reinforce the inclusion of CLN2 in the differential diagnosis of children presenting with seizures, behavioural disorders and language abnormalities. Early diagnosis will allow early initiation of specific therapy.

Leigh syndrome is an early onset progressive disorder caused by defects in mitochondrial oxidative phosphorylation. Pathogenic variants in nuclear and mitochondrial genes are associated with the syndrome. Homozygous pathogenic variants in the C12orf65 gene impair the mitochondrial oxidative phosphorylation system. We describe a new case of Leigh syndrome caused by a novel pathogenic variant of the C12orf65 gene resulting in the lack of the Gly-Gly-Gln (GGQ) domain in the predicted protein, and review clinical and molecular data from previously reported patients. Our study supports that the phenotype caused by C12orf65 gene variants is heterogeneous and varies from spastic paraparesis to Leigh syndrome. Loss-of-function variants are more likely to cause the disease, and variants affecting the GGQ domain tend to be associated with more severe phenotypes, reinforcing a possible genotype-phenotype correlation.

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<b><i>Background:</i></b> Fabry disease (FD) is a rare X-linked storage disorder resulting from the deficient activity of the lysosomal hydrolase α-galactosidase A (α-Gal A). Here we describe a 23-year-old man with FD possessing a novel mutation in the <i>GLA</i> gene, the evaluation of his family, and the functional characterization of the novel variant. <b><i>Methods:</i></b> Two generations of a family were screened for FD by clinical symptoms and low enzymatic activity. This step was followed by DNA sequencing that showed a novel <i>GLA</i> missense mutation. To confirm the pathogenicity potential of the mutation, we employed site-directed polymerase chain reaction mutagenesis. <i>GLA</i> wild-type and mutant plasmids were transfected into mammalian cells; RNA and proteins were extracted for expression and analysis of enzymatic activity. <b><i>Results:</i></b> The patient presents the variant p.Asn34Asp in the <i>GLA</i> and had several manifestations of FD since adolescence. The investigation of the deficiency of α-Gal A was initiated due to stage 4 of chronic kidney disease. All family members carrying the novel mutation presented early symptoms, including index case’s mother, who received a renal transplant when she was 35 years old. <i>In silico</i> and in vitro analysis confirmed the pathogenic potential of the mutation p.Asn34Asp showing that the enzyme had only 4% of residual activity due to protein misfolding. The ability of the pharmacological chaperone 1-deoxygalactonojirimycin to recover the mutant was confirmed, producing 37.5% of residual activity. <b><i>Conclusion:</i></b> In this work, we present a novel missense mutation in <i>GLA</i> that leads to the production of a catalytically competent α-Gal A, which is degraded before its delivery to the lysosome, promoting severe manifestations of FD, with a very similar disease course in affected men and women.

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