Alice Brinckmann Oliveira Netto

Spinal muscular atrophy (SMA) is considered one of the most common autosomal recessive disorders, with an estimated incidence of 1 in 10,000 live births. Testing for SMA has been recommended for inclusion in neonatal screening (NBS) panels since there are several therapies available and there is evidence of greater efficacy when introduced in the pre/early symptomatic phases. In the present study, dried blood spot samples collected by the Reference Services of Neonatal Screening of the Brazilian states of Rio Grande do Sul, Sao Paulo, Mato Grosso and Bahia to perform the routine NBS panel were also screened for 5q-SMA, using real-time PCR (SALSA MC002 technique). In this study, samples from 80,000 newborns were analyzed, enabling the identification of 7 5q-SMA cases, which were confirmed by multiplex ligation-dependent probe amplification (MLPA). Considering our findings, Brazil has an incidence of 5q-SMA of 1 in 11,428 live births. This work expands regional knowledge about the incidence of SMA and is fundamental for planning the implementation of screening for this condition in Brazil.

Mucopolysaccharidosis type IIIB (MPS IIIB, or Sanfilippo syndrome type B) is a lysosomal storage disorder caused by variants in the NAGLU gene, leading to heparan sulfate accumulation. This study analyzed 27 MPS IIIB Brazilian patients diagnosed via the MPS Brazil Network (2014-2022). Diagnosis involved biochemical tests [NAGLU enzyme activity, urinary glycosaminoglycans (GAG)], showing expected low activity of the enzyme and high concentration of GAGs. Molecular analysis of the NAGLU gene by Sanger sequencing or Targeted Next-Generation Sequencing confirmed the diagnosis. Forty-nine variants were found across patient alleles, comprising twenty-two different variants. Two variants were described for the first time: p.Gly79Arg and p.Leu598Pro (both missense). In silico tools predicted the novel variants as damaging/deleterious. The study identified 90.7% of the expected mutant alleles, observing variant heterogeneity and a higher frequency of missense variants. This characterization enhances understanding of the Brazilian MPS IIIB genetic landscape and is instrumental to the design of diagnostic and screening strategies.

Preterm birth (PTB) is the main condition related to perinatal morbimortality worldwide. The aim of this study was to identify gene-environment interactions associated with spontaneous PTB or its predictors. We carried out a retrospective case-control study including parental sociodemographic and obstetric data as well as newborn genetic variants of 69 preterm and 61 at term newborns born at a maternity hospital from Tucumán, Argentina, between 2005 and 2010. A data-driven Bayesian network including the main PTB predictors was created where we identified gene-environment interactions. We used logistic regressions to calculate the odds ratios and confidence intervals of the interactions. From the main PTB predictors (nine exposures and six genetic variants) we identified an interaction between low neighbourhood socioeconomic status and rs2074351 (PON1, genotype GG) variant that was associated with an increased risk of toxoplasmosis (odds ratio 12.51, confidence interval 95%: 1.71 - 91.36). The results of this exploratory study suggest that structural social disparities could influence the PTB risk by increasing the frequency of exposures that potentiate the risk associated with individual characteristics such as genetic traits. Future studies with larger sample sizes are necessary to confirm these findings.

Niemann-Pick disease type C (NPC) is a lysosomal disorder caused by impaired cholesterol metabolism. Levels of lysosphingomyelin 509 (LysoSM509) have been shown elevated in dried blood spots (DBS) of NPC and acid sphingomyelinase deficiency patients. In this study, we report our experience using a two-tier approach (1st tier is the quantification of lysoSM509 by ultra-performance liquid chromatography tandem mass spectrometry followed by the 2nd tier with next-generation sequencing of the NPC1 and NPC2 genes). DBS samples from 450 suspected patients were received by the NPC Brazil network. Of these, 33 samples had elevated levels of lysoSM509, and in 25 of them, variants classified as pathogenic, likely pathogenic, or of unknown significance were identified in the NPC1 or NPC2 genes by next-generation sequencing. The quantification of lysoSM509 in DBS as a first-tier test for the diagnosis of NPC followed by molecular analysis of the NPC1 and NPC2 genes almost doubled the detection rate when compared to the performance of chitotriosidase activity as a first-tier biomarker, and it could likely be increased with the addition of a third tier with MLPA of the two genes involved. This strategy seems suitable for the neonatal screening (NBS) of NPC if this disease is eventually adopted by NBS programs.

Newborn screening enables the diagnosis of treatable disorders at the early stages, and because of its countless benefits, conditions have been continuously added to screening panels, allowing early intervention, aiming for the prevention of irreversible manifestations and even premature death. Mucopolysaccharidoses (MPS) are lysosomal storage disorders than can benefit from an early diagnosis, and thus are being recommended for newborn screening. They are multisystemic progressive disorders, with treatment options already available for several MPS types. MPS I was the first MPS disorder enrolled in the newborn screening (NBS) panel in the USA and a few other countries, and other MPS types are expected to be added. Very few studies about NBS for MPS in Latin America have been published so far. In this review, we report the results of pilot studies performed in Mexico and Brazil using different methodologies: tandem mass spectrometry, molecular analysis, digital microfluidics, and fluorimetry. These experiences are important to report and discuss, as we expect to have several MPS types added to NBS panels shortly. This addition will enable timely diagnosis of MPS, avoiding the long diagnostic odyssey that is part of the current natural history of this group of diseases, and leading to a better outcome for the affected patients.