Investigation of 5-HTT expression using quantitative real-time PCR in the human brain in SIDS Italian cases

Revisiting the Neuropathology of Sudden Infant Death Syndrome (SIDS)

Background: Sudden infant death syndrome (SIDS) is one of the leading causes of infant mortality in the United States (US). The extent to which SIDS manifests with an underlying neuropathological mechanism is highly controversial. SIDS correlates with markers of poor prenatal and postnatal care, generally rooted in the lack of access and quality of healthcare endemic to select racial and ethnic groups, and thus can be viewed in the context of health disparities. However, some evidence suggests that at least a subset of SIDS cases may result from a neuropathological mechanism. To explain these issues, a triple-risk hypothesis has been proposed, whereby an underlying biological abnormality in an infant facing an extrinsic risk during a critical developmental period SIDS is hypothesized to occur. Each SIDS decedent is thus thought to have a unique combination of these risk factors leading to their death. This article reviews the neuropathological literature of SIDS and uses machine learning tools to identify distinct subtypes of SIDS decedents based on epidemiological data.

Methods: We analyzed US Period Linked Birth/Infant Mortality Files from 1990 to 2017 (excluding 1992–1994). Using t-SNE, an unsupervised machine learning dimensionality reduction algorithm, we identified clusters of SIDS decedents. Following identification of these groups, we identified changes in the rates of SIDS at the state level and across three countries.

Results: Through t-SNE and distance based statistical analysis, we identified three groups of SIDS decedents, each with a unique peak age of death. Within the US, SIDS is geographically heterogeneous. Following this, we found low birth weight and normal birth weight SIDS rates have not been equally impacted by implementation of clinical guidelines. We show that across countries with different levels of cultural heterogeneity, reduction in SIDS rates has also been distinct between decedents with low vs. normal birth weight.

Conclusions: Different epidemiological and extrinsic risk factors exist based on the three unique SIDS groups we identified with t-SNE and distance based statistical measurements. Clinical guidelines have not equally impacted the groups, and normal birth weight infants comprise more of the cases of SIDS even though low birth weight infants have a higher SIDS rate.

No association to sudden infant death syndrome detected by targeted amplicon sequencing of 24 genes

AIM

The aim was to identify genetic variants associated with sudden infant death syndrome (SIDS) that can cause disease or introduce vulnerability. Genes reported in a previous SIDS study to have altered messenger ribonucleic acid (mRNA) expression in SIDS were investigated.

METHODS

Samples from 81 SIDS (56 male/28 female) with a median age of 4 months (range 0.75-9 months) were analysed using Illumina TruSeq custom amplicon for 24 selected genes. Samples were collected from autopsy at Oslo university hospital from children whom died suddenly and unexpectedly from 1988 to 2006. The controls were the germline variation database, Norgene (no description of cases available).

RESULTS

After filtering for rare variants, there were a total of 38 variants in the 81 SIDS cases and 462 variants in the 789 controls. After the filtration and curation steps, we found 36 rare variants. The overall occurrence of rare variants for all the SIDS samples was lower than for the Norgene population.

CONCLUSION

There was no association between rare variants in the included genes and SIDS. Although not statistically significant, two of the SIDS cases had a rare variant in the MyD88 gene: rs746651350, rs200424253.

A Systematic Review of Molecular Autopsy Studies in Sudden Infant Death Cases

Sudden unexpected death is an upsetting event, which can remain unexplained even after post-mortem investigation. Internationally, molecular autopsies have shown to resolve up to 44% of unexplained cases; however, it is currently unclear how many of these were infants. This systematic literature review showed that significantly fewer infant cases were resolved (median: 4%) compared with cohorts of 1 to 45 years old (median: 32%). Further, no study involving indigenous African participants has yet been published. Overall, molecular autopsies hold immense value to living family members and is motivation to explore new avenues in infant cohorts.

The First 5-Year-Long Survey on Intrauterine Unexplained Sudden Deaths from the Northeast Italy

PURPOSE

Sudden intrauterine unexplained death syndrome (SIUDS) represents one of the main open issues in the scientific and social setting of the modern medicine, and our efforts have aimed to understand its possible causes and risk factors.

METHODS

A 43-case series of consecutive unexplained fetal deaths coming from Northeast Italy, collected in a 5-year period (2011-2015), has been submitted to an in-depth investigation, based on neuropathological and cardiopathological examinations, immunohistochemistry for neuronal nuclear antigen (NeuN), genetic characterization for the serotonin transporter (5-HTT) gene polymorphisms, and toxicological environmental analyses.

RESULTS

The overall survey from the neuropathological findings highlights one or more congenital morphological abnormalities of the autonomic nervous system in 77% of cases of sudden fetal deaths.

CONCLUSIONS

From our results emerges the need to perform a complete autopsy of all SIUDS victims with an in-depth examination of the neuronal centers of the brainstem, which modulate the vital functions.