Genetics of the sudden infant death syndrome

Sudden Infant Death Syndrome: Risk Factors and Newer Risk Reduction Strategies

Sudden infant death syndrome (SIDS) continues to be one of the top causes of infant death in the U.S. Despite significant public health initiatives focused on high-risk populations to enhance sleep environments and techniques. The SIDS rate has remained stable in recent years. Risk factors and newer risk reduction strategies for SIDS are the focus of this review article. We conducted a comprehensive literature search on Medline, Cochrane, Embase, and Google Scholar until July 2022. The following search strings and Medical Subject Heading (MeSH) terms were used: "SIDS," "Sudden Infant Death" and "SUID". We explored the literature on SIDS for its epidemiology, pathophysiology, the role of various etiologies and their influence, associated complications leading to SIDS, and preventive and treatment modalities. Despite a more than 50% drop-in rates since the start of the "Back to Sleep" campaign in 1994, sudden infant death syndrome (SIDS) continues to be the top cause of post-neonatal mortality in the United States, despite continued educational initiatives that support safe sleep and other risk reduction strategies. The new American Academy of Pediatrics guidelines for lowering the risk of SIDS include a lot of emphasis on sleeping habits, bedding, and environment but also include elements that are frequently ignored (i.e., prenatal care, smoking, alcohol and drug use, and childhood vaccinations). This study highlights these less-frequently discussed aspects and identifies treatments that have produced beneficial behavioral shifts that benefit newborns as well as their mothers' health and wellbeing.

Non-polyalanine repeat mutation in PHOX2B is detected in autopsy cases of sudden unexpected infant death

Background

Congenital central hypoventilation syndrome (CCHS), which is caused by PHOX2B with phenotypic variations, has a point of controversy: CCHS is putatively involved in autopsy cases of sudden unexpected infant death (SUID) including sudden infant death syndrome.

Objective

The relation of CCHS to SUID cases was investigated by extensive genotyping of PHOX2B.

Methods

We analyzed 93 DNA samples of less than one-year-old SUID cases that were autopsied in our department. Unrelated adult volunteers (n = 942) were used as the control.

Results

No polyalanine tract expansion was detected in the SUID cases. The allelic frequencies of repeat contractions and SNP (rs28647582) in intron 2 were not significantly different from that in those control group. Further extensive sequencing revealed a non-polyalanine repeat mutation (NPARM) of c.905A>C in a sudden death case of a one-month-old male infant. This missense mutation (p.Asn302Thr), registered as rs779068107, was annotated to ‘Affected status is unknown’, but it might be associated with the sudden death.

Conclusion

NPARM was more plausibly related to sudden unexpected death than expansions because of severe clinical complications. This finding indicates possible CCHS involvement in forensic autopsy cases without ante-mortem diagnosis.

Is There a Role for the Microbiome and Sudden Death? A Systematic Review

Background. Sudden unexpected death (SUD) is one of the most important and worthy investigation case profiles in emergency medicine and forensic pathology. Sudden unexpected deaths in adults (SUDA) are frequently caused by cardiac events, while infections usually cause those in infants younger than one year (SUDI), and to a lesser extent, in children older than one year (SUDC). However, in some instances of children under the age of one dying (SIDS), a cause is not discovered despite a thorough investigation that includes a review of clinical history, examination of the death scene, and a complete autopsy. Several studies demonstrate that the microbiome influences host immunity, alters susceptibility to viral respiratory infections, and has a vital role in various health, disease, and death outcomes. The main objective of this systematic review was to compile and offer a complete vision of the main lines of research on microbiome and sudden death that have emerged in recent years and their relationship with forensic sciences, as well as the possible contributions or limitations in the field of forensic sciences. Methods. Following PRISMA principles, a systematic evaluation of the microbiome and sudden death in forensic science was conducted. In this review, our study classified the sudden deaths as SUDA, SUDI, and SIDS. Results. The role of microbiome research in sudden death is discussed in this review. Various studies have linked the detection of different bacteria or viruses as a probable cause of sudden death. Bacteria analysed differ between studies that used autopsy specimens from deaths classified as SUDA, SUDI, and SIDS, or, except in the case of Staphylococcus aureus and Escherichia coli, which have been analysed in both SUDI and SIDS autopsies. In the case of viruses, only Cytomegalovirus has been analysed in both SIDS and SUDI cases. However, all the viruses studied are respiratory viruses found in samples of nasopharyngeal or lung fluid. Conclusions. Although the application of the microbiome in sudden death and other fields of forensic science is still in its early stages, a role of the microbiome in sudden deaths cannot be ruled out, but we cannot conclude that it is a significant factor either.

Association between monoamine oxidase A promoter polymorphism and the risk of sudden infant death syndrome: a meta-analysis

Introduction

The etiology of sudden infant death syndrome (SIDS) remains an unsolved problem. The aim of this meta-analysis is to investigate the potential association between monoamine oxidase A (MAOA) promoter variable number tandem repeat (VNTR) polymorphism and SIDS risk.

Methods

A systematic review and meta-analysis were conducted on studies from accessible electronic databases. Each VNTR variant was examined in each gender independently by comparing with the pooled results of other alleles.

Results

A total of six independent case–control studies including 1022 SIDS cases and 1839 controls were enrolled in this meta-analysis. In both of the whole populations and Caucasian populations, male infants with the low-MAOA-expression alleles (2R+3R) were found to exhibit a statistically significant increased risk of SIDS, whereas those with a 4R allele exhibited a reduced risk of SIDS. Besides, an increased risk of SIDS was detected in male Caucasian infants with 2R or 3R alleles. However, none of the allele or genotype variants was associated with SIDS in female victims.

Conclusion

In male Caucasian infants, the low expression of MAOA promoter VNTR alleles (2R and 3R) is associated with an increased risk of SIDS, and the existence of the 4R allele could be regarded as a protective factor.

Comprehensive Analysis of Genes Associated With Sudden Infant Death Syndrome

Background: Sudden infant death syndrome (SIDS) is a tragic incident which remains a mystery even after post-mortem investigation and thorough researches. Methods: This comprehensive review is based on the genes reported in the molecular autopsy studies conducted on SIDS so far. A total of 20 original studies and 7 case reports were identified and included in this analysis. The genes identified in children or adults were not included. Most of the genes reported in these studies belonged to cardiac channel and cardiomyopathy. Cardiac channel genes in SIDS were scrutinized for further analysis. Results: After screening and removing the duplicates, 42 unique genes were extracted. When the location of these genes was assessed, it was observed that most of these belonged to Chromosomes 11, 1 and 3 in sequential manner. The pathway analysis shows that these genes are involved in the regulation of heart rate, action potential, cardiac muscle cell contraction and heart contraction. The protein-protein interaction network was also very big and highly interactive. SCN5A, CAV3, ALG10B, AKAP9 and many more were mainly found in these cases and were regulated by many transcription factors such as MYOG C2C1 and CBX3 HCT11. Micro RNA, "hsa-miR-133a-3p" was found to be prevalent in the targeted genes. Conclusions: Molecular and computational approaches are a step forward toward exploration of these sad demises. It is so far a new arena but seems promising to dig out the genetic cause of SIDS in the years to come.

Molecular autopsy in a cohort of infants died suddenly at rest

Sudden infant death syndrome is the leading cause of death during the first year of life. A large part of cases remains without a conclusive cause of death after complete autopsy. In these situations, cardiac arrhythmia of genetic origin is suspected as the most plausible cause of death. Our aim was to ascertain whether genetic variants associated with sudden cardiac death might be the cause of death in a cohort of infants died suddenly. We analyzed 108 genes associated with sudden cardiac death in 44 post-mortem samples of infants less than 1 year old of age who died at rest. Definite cause of death was not conclusive in any case after a complete autopsy. Genetic analysis identified at least one rare variant in 90.90% of samples. A total of 121 rare genetic variants were identified. Of them, 33.05% were novel and 39.66% were located in genes encoding ion channels or associated proteins. A comprehensive genetic analysis in infants who died suddenly enables the unraveling of potentially causative cardiac variants in 2045% of cases. Molecular autopsy should be included in forensic protocols when no conclusive cause of death is identified. Large part genetic variants remain of uncertain significance, reinforcing the crucial role of genetic interpretation before clinical translation but also in early identification of relatives at risk.

The Evolving Understanding of Sudden Unexpected Infant Death

Sudden unexpected infant death (SUID) is the leading cause for post-neonatal mortality in industrialized nations. Case-control studies have identified risk factors for SUID that have shaped research into studies of causation. Most current hypotheses for the mechanisms for SUID contribute to the "SUID sequence"-hypoxia and/or hypercarbia in sleep to which a vulnerable infant fails to respond adequately and that results in death. Reducing vulnerability in infants and promoting safe sleep for infants is important for prevention and requires knowledge of the prevalence of risk factors within the target population and a culturally sensitive approach. [Pediatr Ann. 2017;46(8):e278-e283.].

Infection: the neglected paradigm in SIDS research

Despite decades of investigation and millions of dollars spent, the cause of sudden infant death syndrome (SIDS) eludes researchers. It is timely therefore to reconsider the reasons for this failure and to explore how research might go forward with better prospects. This review assesses SIDS research in the context of clinicopathological and epidemiological features and determines that only infection attains congruence.

Post-mortem whole-exome analysis in a large sudden infant death syndrome cohort with a focus on cardiovascular and metabolic genetic diseases

Sudden infant death syndrome (SIDS) is described as the sudden and unexplained death of an apparently healthy infant younger than one year of age. Genetic studies indicate that up to 35% of SIDS cases might be explained by familial or genetic diseases such as cardiomyopathies, ion channelopathies or metabolic disorders that remained undetected during conventional forensic autopsy procedures. Post-mortem genetic testing by using massive parallel sequencing (MPS) approaches represents an efficient and rapid tool to further investigate unexplained death cases and might help to elucidate pathogenic genetic variants and mechanisms in cases without a conclusive cause of death. In this study, we performed whole-exome sequencing (WES) in 161 European SIDS infants with focus on 192 genes associated with cardiovascular and metabolic diseases. Potentially causative variants were detected in 20% of the SIDS cases. The majority of infants had variants with likely functional effects in genes associated with channelopathies (9%), followed by cardiomyopathies (7%) and metabolic diseases (1%). Although lethal arrhythmia represents the most plausible and likely cause of death, the majority of SIDS cases still remains elusive and might be explained by a multifactorial etiology, triggered by a combination of different genetic and environmental risk factors. As WES is not substantially more expensive than a targeted sequencing approach, it represents an unbiased screening of the exome, which could help to investigate different pathogenic mechanisms within the genetically heterogeneous SIDS cohort. Additionally, re-analysis of the datasets provides the basis to identify new candidate genes in sudden infant death.

Candidate gene variants of the immune system and sudden infant death syndrome

BACKGROUND

Sudden infant death syndrome (SIDS) causes early infant death with an incidence between 0.5 and 2.5 cases among 1000 live births. Besides central sleep apnea and thermal dysregulation, infections have been repeatedly suggested to be implicated in SIDS etiology.

METHODS

To test the risk contribution of common genetic variants related to infection, we genotyped 40 single-nucleotide polymorphisms (SNPs) from 15 candidate genes for association with SIDS in a total of 579 cases and 1124 controls from Germany and the UK in a two-stage case control design.

RESULTS

The discovery-stage series (267 SIDS cases and 303 controls) revealed nominally significant associations for variants in interleukin 6 (IL6) (rs1880243), interleukin 10 (IL10) (rs1800871, rs1800872), and mannose-binding lectin 2 (MBL2) (rs930506), and for several other variants in subgroups. Meta-analyses were then performed in adding genotype information from a genome-wide association study of another 312 European SIDS cases and 821 controls. Overall associations were observed for two independent variants in MBL2: rs930506 in a co-dominant model (odds ratio (OR) = 0.82, p = 0.04) and rs1838065 in a dominant model (OR = 1.27, p = 0.03).

CONCLUSION

Our study did not replicate published associations of IL10 variants with SIDS. However, the evidence for two independent MBL2 variants in the combined analysis of two large series seems consistent with the hypothesis that infection may play a role in SIDS pathogenesis.

Sudden infant death syndrome caused by cardiac arrhythmias: only a matter of genes encoding ion channels?

Sudden infant death syndrome is the unexpected demise of a child younger than 1 year of age which remains unexplained after a complete autopsy investigation. Usually, it occurs during sleep, in males, and during the first 12 weeks of life. The pathophysiological mechanism underlying the death is unknown, and the lethal episode is considered multifactorial. However, in cases without a conclusive post-mortem diagnosis, suspicious of cardiac arrhythmias may also be considered as a cause of death, especially in families suffering from any cardiac disease associated with sudden cardiac death. Here, we review current understanding of sudden infant death, focusing on genetic causes leading to lethal cardiac arrhythmias, considering both genes encoding ion channels as well as structural proteins due to recent association of channelopathies and desmosomal genes. We support a comprehensive analysis of all genes associated with sudden cardiac death in families suffering of infant death. It allows the identification of the most plausible cause of death but also of family members at risk, providing cardiologists with essential data to adopt therapeutic preventive measures in families affected with this lethal entity.

Sudden unexpected death in infancy: biological mechanisms

Sudden unexpected death in infancy (SUDI) covers both explained and unexplained deaths. Unexplained cases or SIDS are likely to have multiple neural mechanisms contributing to the final event. The evidence ranges from subtle physiological signs related to autonomic control, to findings at autopsy of altered neurotransmitter systems, including the serotonergic system, a network that has an extensive homeostatic role in cardio-respiratory and thermoregulatory control. Processes may be altered by the vulnerability of the infant due to age, poor motor ability, or a genetic predisposition. The fatal event may occur in response to an environmental stress. A single final physiological route to death seems unlikely. An understanding of the reasons for explained SUDI also reminds us that a thorough investigation is required after each death occurs.

Variants in TSPYL1 are not associated with sudden infant death syndrome in a cohort of deceased infants from Switzerland

Sudden infant death syndrome (SIDS) is currently the major cause of an unexpected and unexplained death of infants in the first year of lifetime in industrialized countries. Besides environmental factors also genetic factors have been identified as risk factors for SIDS. Notably, the mutation c.457dupG (p.Glu153Glyfs*17) in the TSPYL1 gene has been reported to cause autosomal recessive sudden infant death with dysgenesis of the testes syndrome (SIDDT) in an Old Order Amish community in Pennsylvania. The purpose of this study was to analyze whether variants of TSPYL1 are associated with the sudden infant death syndrome (SIDS) in the area of Europe from which the Amish descended. Mutation analysis of the entire TSPYL1 gene was performed in a cohort of 165 SIDS cases with mostly Swiss ethnic origin, in comparison to 163 German controls. Eight known polymorphisms were detected, none of which was significantly associated with SIDS. One deceased girl was heterozygous for the hitherto unreported TSPYL1 variant c.106C>G (p.Leu36Val), and two affected girls were heterozygous for the rare known TSPYL1 variant rs140756663 (c.1098C>A, p.Phe366Leu). In addition, one deceased boy was heterozygous for the rare common silent nucleotide substitution c.718C>T (p.Leu240Leu, rs150144081), while one control was heterozygous for the rare silent nucleotide substitution rs56190632 (c.760C>T; p.Leu254Leu). In silico analyses predicted a likely non-pathogenic effect for p.Leu36Val and p.Phe366Leu, respectively, although protein features might be affected. The Amish founder mutation was not detected in the analyzed SIDS cases and controls. Mutations and polymorphisms in the TSPYL1 gene were not associated with SIDS in a cohort of 165 deceased Swiss infants.

Aquaporin-4 polymorphisms and brain/body weight ratio in sudden infant death syndrome (SIDS)

BACKGROUND

Failure in the regulation of homeostatic water balance in the brain is associated with severe cerebral edema and increased brain weights and may also play an important role in the pathogenesis of sudden infant death syndrome (SIDS). We genotyped three single-nucleotide polymorphisms in the aquaporin-4 water channel-encoding gene (AQP4), which were previously shown to be associated with (i) SIDS in Norwegian infants (rs2075575), (ii) severe brain edema (rs9951307), and (iii) increased brain water permeability (rs3906956). We also determined whether the brain/body weight ratio is increased in SIDS infants compared with sex- and age-matched controls.

METHODS

Genotyping of the three AQP4 single-nucleotide polymorphisms was performed in 160 Caucasian SIDS infants and 181 healthy Swiss adults using a single-base extension method. Brain and body weights were measured during autopsy in 157 SIDS and 59 non-SIDS infants.

RESULTS

No differences were detected in the allelic frequencies of the three AQP4 single-nucleotide polymorphisms between SIDS and adult controls. The brain/body weight ratio was similarly distributed in SIDS and non-SIDS infants.

CONCLUSION

Variations in the AQP4 gene seem of limited significance as predisposing factors in Caucasian SIDS infants. Increased brain weights may only become evident in conjunction with environmental or other genetic risk factors.

The role of clinical, genetic and segregation evaluation in sudden infant death

Sudden infant death syndrome (SIDS) is the leading cause of death in the first year of life. Several arrhythmogenic genes have been associated with cardiac pathologies leading to infant sudden cardiac death (SCD). Our aim was to take advantage of next generation sequencing (NGS) technology to perform a thorough genetic analysis of a SIDS case. A SIDS case was referred to our institution after negative autopsy. We performed a genetic analysis of 104 SCD-related genes using a custom panel. Confirmed variants in index case were also analyzed in relatives. Clinical evaluation of first-degree family members was performed. Relatives did not show pathology. NGS identified seven variants. Two previously described as pathogenic. Four previously catalogued without clinical significance. The seventh variation was novel. Familial segregation showed that the index case's mother carried all same genetic variations except one, which was inherited from the father. The sister of the index case carried three variants. We believe that molecular autopsy should be included in current forensic protocols after negative autopsy. In addition to NGS technologies, familial genetic testing should be also performed to clarify potential pathogenic role of new variants and to identify genetic carriers at risk of SCD.

Functional single-nucleotide variant of HSPD1 in sudden infant death syndrome

BACKGROUND

An insufficient stress response due to a genetically impaired heat shock protein (Hsp) could play a role in the pathogenesis in a subgroup of sudden infant death syndrome (SIDS) cases. Herein, we are the first to investigate whether a functionally impairing and thus pathogenic variant of the gene for Hsp60, encoded by HSPD1 (rs72466451), is correlated with the occurrence of SIDS.

METHODS

In a case-control study of a series of 133 cases of SIDS and 192 gender-matched German Caucasian control cases, the occurrence and distribution of the HSPD1 single-nucleotide variant (SNV) was analyzed using SNV genotyping by minisequencing.

RESULTS

The results show significantly increased frequency of the pathogenic variant of the HSPD1 SNV in a subgroup (4.5%) of SIDS cases.

CONCLUSION

The results suggest that the pathogenic variant of rs72466451 may play a role in a subgroup of SIDS cases with impaired Hsp60-mediated stress response.

Mutations in genes encoding cardiac ion channels previously associated with sudden infant death syndrome (SIDS) are present with high frequency in new exome data

BACKGROUND

Sudden infant death syndrome (SIDS) is the leading cause of death in the first 6 months after birth in the industrialized world. The genetic contribution to SIDS has been investigated intensively and to date, 14 cardiac channelopathy genes have been associated with SIDS. Newly published data from National Heart, Lung, and Blood Institute Grand Opportunity (NHLBI GO) Exome Sequencing Project (ESP) provided important knowledge on genetic variation in the background population. Our aim was to identify all variants previously associated with SIDS in ESP to improve the discrimination between plausible disease-causing mutations and variants most likely to be false-positive.

METHODS

The PubMed database was searched to identify SIDS-associated channelopathy variants and the prevalence of these in the ESP population (6500 individuals) were obtained. In silico prediction tools were applied to variants present in ESP and 6 SIDS-associated variants (CAV3 p.C72W, p.T78M; KCNH2 p.R148W, and SCN5A p.S216L, p.V1951L, p.F2004L) were genotyped in our own control population.

RESULTS

Nineteen different missense variants previously associated with SIDS were identified in ESP affecting 225 of 6424 alleles. This corresponds to 1:29 individuals in the ESP population being carriers of a SIDS-associated variant. Genotyping of 6 SIDS-associated variants in our own controls revealed frequencies comparable with those found in ESP.

CONCLUSIONS

A very high prevalence of previously SIDS-associated variants was identified in exome data from population studies. Our findings indicate that the suggested disease-causing role of some of these variants is questionable. A cautious interpretation of these variants must be made when found in SIDS victims.

Sociodemographic and meteorological correlates of sudden infant death in Taiwan

BACKGROUND

This study was designed, using three national datasets including the Taiwan Death Registry, Taiwan Birth Registry, and National Meteorological Dataset, to examine the sociodemographic, geographic and meteorological correlates of sudden infant death syndrome (SIDS).

METHODS

One thousand, six hundred and seventy-one cases of SIDS occurring between 1994 and 2003, and 8355 matched controls were included in this nested case-control study.

RESULTS

Over the study period, the annual rate of SIDS declined only slightly, with an average annual rate of 57.9/10(5) . Male infants (adjusted odds ratio [AOR], 1.19; 95% confidence interval [CI]: 1.06-1.33), preterm births (AOR, 1.69; 95%CI: 1.33-2.13), low birthweight (AOR, 2.87; 95%CI: 2.30-3.59), and birth order ≥3 (AOR, 1.62; 95%CI: 1.37-1.92) were the demographic risk factors for SIDS. Additionally, paternal age <25 years (AOR, 1.37; 95%CI: 1.09-1.71), urbanization (AOR, 1.46; 95%CI: 1.20-1.78), lower paternal education (elementary and less; AOR, 1.28; 95%CI: 1.01-1.64), and parental age difference >10 years (AOR, 1.72; 95%CI: 1.24-2.39) were also associated with increased risk of SIDS. It was also noted that daily average temperature ranging from 9.2°C to 14.2°C (AOR, 2.10; 95%CI: 1.67-2.64) was associated with the most increased risk, while temperature ≥26.4°C (AOR 0.60, 0.61) was significantly associated with the most reduced risk.

CONCLUSION

Sociodemographic, geographic and meteorological data can be used to identify families in greater need of early guidance and to promote various prevention measures to avoid the occurrence of SIDS.

Star-crossed? The association of the 5-HTTLPR s allele with season of birth in a healthy female population, and possible consequences for temperament, depression and suicide

BACKGROUND

Birth season has well-known effects on neuropsychiatric disorders, and may also influence genotype distribution by possibly influencing chance of conception via parental idiosyncratic conception patterns or survival of foetuses or infants. The 5-HTTLPR is associated with phenomena including affective temperaments or suicide which are also associated with birth season. Our aim was to investigate the association of 5-HTTLPR genotype and birth season in a healthy female population.

METHODS

Birth date and 5-HTTLPR genotype was determined for 327 psychiatrically healthy women. The association between presence of s allele and time of birth was analysed using generalized linear models.

RESULTS

A significant association between s allele frequency and time of birth was detected. S allele carrier frequency was marginally significantly higher in July borns and significantly lower in autumn borns.

LIMITATIONS

We investigated an adult sample so genotype frequency data do not reflect birth frequencies. Our sample consisted exclusively of females.

CONCLUSIONS

There is no clear explanation for the observed association, although idiosyncratic parental conception patterns, the association of 5-HTTLPR with sudden infant/intrauterine death, or other s allele-mediated behaviours may play a role. Our results are strikingly parallel with earlier data reporting a higher risk of completed suicide in July borns, and higher scores of July borns and lower scores of autumn borns on certain affective temperament scales, both of which are also associated with the s allele of 5-HTTLPR. Thus our results may add to the growing body of evidence regarding the etiological background of affective disorders.

Cardiac ion channelopathies and the sudden infant death syndrome

The sudden infant death syndrome (SIDS) causes the sudden death of an apparently healthy infant, which remains unexplained despite a thorough investigation, including the performance of a complete autopsy. The triple risk model for the pathogenesis of SIDS points to the coincidence of a vulnerable infant, a critical developmental period, and an exogenous stressor. Primary electrical diseases of the heart, which may cause lethal arrhythmias as a result of dysfunctioning cardiac ion channels (“cardiac ion channelopathies”) and are not detectable during a standard postmortem examination, may create the vulnerable infant and thus contribute to SIDS. Evidence comes from clinical correlations between the long QT syndrome and SIDS as well as genetic analyses in cohorts of SIDS victims (“molecular autopsy”), which have revealed a large number of mutations in ion channel-related genes linked to inheritable arrhythmogenic syndromes, in particular the long QT syndrome, the short QT syndrome, the Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia. Combining data from population-based cohort studies, it can be concluded that at least one out of five SIDS victims carries a mutation in a cardiac ion channel-related gene and that the majority of these mutations are of a known malignant phenotype.

Serotonin transporter role in identifying similarities between SIDS and idiopathic ALTE

OBJECTIVE

Considering previous genetic studies on sudden infant death syndrome (SIDS) and the role of L/L serotonin transporter (5HTT) genotype and correlated genes monoamine oxidase A (MAOA) and dopamine transporter (DAT) in unexpected death, an investigation was carried out verifying their involvement in apparent life-threatening events (ALTE and idiopathic form [IALTE]), also assessing common molecular basis with SIDS.

METHODS

Differential diagnoses in 76 ALTE infants, distinguishing ALTE from IALTE was elaborated by using clinical-diagnostic data. Genotypes/allelic frequencies of DAT, MAOA, and 5HTT were determined in ALTE and IALTE infants and compared with data obtained from 20 SIDS and 150 controls.

RESULTS

No association was found between DAT polymorphisms and ALTE/IALTE groups either at the genotype or allelic level (P range .11-.94). MAOA genotypes and allele data comparison between ALTE and controls was not significant; IALTE data showed a tendency for genotypes (P = .09) and were statistically significant for alleles (P = .036); however, MAOA significance disappeared once the Bonferroni correction was applied. 5HTT polymorphisms in IALTE remarked the role of L/L genotype (P < .00001) and L (P < .00001), as previously demonstrated in SIDS.

CONCLUSIONS

Considering correspondence between 5HTT and MAOA in IALTE and SIDS, we hypothesize that the 2 syndromes are different expressions of a common ethiopathogenesis. In particular, genetic data suggest SIDS events could derive from IALTE episodes occurred during sleep, and therefore out of parental control. Despite its functional role, results highlight the usefulness of 5HTT as a valuable tracer of SIDS risk in IALTE infants. Owing to the small sample size, the results are to be considered preliminary and should be reevaluated in an independent sample.

Apnea of prematurity: from cause to treatment

Apnea of prematurity (AOP) is a common problem affecting premature infants, likely secondary to a "physiologic" immaturity of respiratory control that may be exacerbated by neonatal disease. These include altered ventilatory responses to hypoxia, hypercapnia, and altered sleep states, while the roles of gastroesophageal reflux and anemia remain controversial. Standard clinical management of the obstructive subtype of AOP includes prone positioning and continuous positive or nasal intermittent positive pressure ventilation to prevent pharyngeal collapse and alveolar atelectasis, while methylxanthine therapy is a mainstay of treatment of central apnea by stimulating the central nervous system and respiratory muscle function. Other therapies, including kangaroo care, red blood cell transfusions, and CO(2) inhalation, require further study. The physiology and pathophysiology behind AOP are discussed, including the laryngeal chemoreflex and sensitivity to inhibitory neurotransmitters, as are the mechanisms by which different therapies may work and the potential long-term neurodevelopmental consequences of AOP and its treatment.

A perspective on SIDS pathogenesis. the hypotheses: plausibility and evidence

Several theories of the underlying mechanisms of Sudden Infant Death Syndrome (SIDS) have been proposed. These theories have born relatively narrow beach-head research programs attracting generous research funding sustained for many years at expense to the public purse. This perspective endeavors to critically examine the evidence and bases of these theories and determine their plausibility; and questions whether or not a safe and reasoned hypothesis lies at their foundation. The Opinion sets specific criteria by asking the following questions: 1. Does the hypothesis take into account the key pathological findings in SIDS? 2. Is the hypothesis congruent with the key epidemiological risk factors? 3. Does it link 1 and 2? Falling short of any one of these answers, by inference, would imply insufficient grounds for a sustainable hypothesis. Some of the hypotheses overlap, for instance, notional respiratory failure may encompass apnea, prone sleep position, and asphyxia which may be seen to be linked to co-sleeping. For the purposes of this paper, each element will be assessed on the above criteria.