Evaluation of diagnostic tools applied in the examination of sudden unexpected deaths in infancy and early childhood

Causes of Sudden Unexpected Death in Childhood: Autopsy Findings from a Specialist Centre

OBJECTIVES

To investigate the aetiologies of sudden unexpected death from natural causes in children aged 1-18 years by retrospective examination of autopsy records from a single centre.

MATERIALS AND METHODS

The post-mortem findings from 548 children (1996-2015) were examined. Details were entered into an established research database and categorized according to >400 pre-defined criteria.

RESULTS

There were 265 previously apparently healthy children and 283 with pre-existing, potentially life-limiting, conditions. There were more males than females (M:F 1.4:1), and deaths were more frequent in the winter. Infection was commonest accounting for 43% of all deaths. Non-infectious diseases were identified as cause of death in 28%, and 29% of all deaths were unexplained. There was no significant difference in the proportions of deaths in each category between the previously healthy children and those with pre-existing conditions.

CONCLUSION

Sudden unexpected death is a rare presentation of death in childhood and those with pre-existing conditions may be more at risk. Standardisation of the post-mortem procedure in such cases may result in more ancillary investigations performed as routine and may reduce the number of cases that are 'unexplained'.

Machine Learning Approaches to Determine Feature Importance for Predicting Infant Autopsy Outcome

INTRODUCTION

Sudden unexpected death in infancy (SUDI) represents the commonest presentation of postneonatal death. We explored whether machine learning could be used to derive data driven insights for prediction of infant autopsy outcome.

METHODS

A paediatric autopsy database containing >7,000 cases, with >300 variables, was analysed by examination stage and autopsy outcome classified as 'explained (medical cause of death identified)' or 'unexplained'. Decision tree, random forest, and gradient boosting models were iteratively trained and evaluated.

RESULTS

Data from 3,100 infant and young child (<2 years) autopsies were included. Naïve decision tree using external examination data had performance of 68% for predicting an explained death. Core data items were identified using model feature importance. The most effective model was XG Boost, with overall predictive performance of 80%, demonstrating age at death, and cardiovascular and respiratory histological findings as the most important variables associated with determining medical cause of death.

CONCLUSION

This study demonstrates feasibility of using machine-learning to evaluate component importance of complex medical procedures (paediatric autopsy) and highlights value of collecting routine clinical data according to defined standards. This approach can be applied to a range of clinical and operational healthcare scenarios.

Discrepancies in Physician and Coroner Findings in Cases of Fatal Suspected Physical Child Abuse

OBJECTIVES

As mandated reporters of suspected abuse, physicians must consider abuse when a child dies unexpectedly. Subsequently, a coroner or medical examiner determines the manner of death (MOD) and cause of death (COD). Accurate diagnoses and determinations are important for social safety and justice. This study described discrepancies between physicians' and coroners' findings in cases of fatal suspected physical child abuse.

METHODS

This study was a single-institution, retrospective review. All children 6 years or younger who died in a pediatric emergency department from October 2006 to January 2013 with a coroner report were included in this study. Coroner reports, MODs, and CODs were reviewed. Skeletal survey results were compared with coroners' findings.

RESULTS

One hundred twenty-nine children were included. The MODs included the following: undetermined, 63 (49%); accident, 32 (25%); natural, 31 (24%); and homicide, 3 (2%). Thirty-three (26%) of the 129 patients had abuse suspected at the time of death in the emergency department; in this subset, MODs were as follows: undetermined, 16 (48%); accident, 8 (24%); natural, 6 (18%); and homicide, 3 (9%). Sudden infant death syndrome or sudden unexpected death was the most common COD in all children (68, 55%). Skeletal surveys were positive in 12 children with 29 fractures identified; 8 (28%) of the 29 fractures were corroborated on autopsy findings. Of the 12 children with positive skeletal survey findings, only 1 was ruled a homicide.

CONCLUSIONS

We found discrepancies between coroner determination of homicide and abuse suspected by physicians, especially among children with fractures. Improved communication between agencies in cases of fatal child abuse is needed.

Prevalence of positive toxicology analysis from the French national registry for sudden unexpected infant death (Tox-MIN)

BACKGROUND

Sudden unexpected infant death (SUID) remains the leading cause of postnatal mortality in many countries. French and international guidelines recommend a thorough examination with toxicology studies.

OBJECTIVES

The main objective was to determine the prevalence of toxic detection and positive analyses. The secondary objectives were to describe the different toxics and compare children with positive (Tox+) and negative results (Tox-) with other SUID risk factors.

DESIGN AND METHODS

We used the data registered from May 2015 to December 2018 by the French national SUID registry (OMIN). It collects data for all SUID cases admitted to any of the 35 participating French SUID referral centers.

RESULTS

Of the 624 SUID cases registered in the OMIN, a post-mortem toxicological analysis was performed in 398 infants. Thirty-six patients (9%) were positives for expected (Etox+ (n = 19 [53%], e.g., resuscitation drugs, regular treatments) and unexpected (UTox+) (n = 17 [47%]) toxics. The unexpected toxics were opioids (n = 8), cannabis (n = 4), cocaine (n = 3), cotinine (n = 2), carbon monoxide (n = 2), caffeine (n = 2), alcohol (n = 1) and GHB (n = 1). UTox + infants had a different seasonal distribution (p = .03), a higher incidence of inappropriate sleeping position and bedding at the time of death (respectively OR 3.8, p = .037 - OR 5.4, p = .026); inadequate body hygiene (OR 10.6, p = .0005), a younger maternal age (p = .045) and a higher rate of maternal drug abuse (OR 21.9, p = .0008).

CONCLUSION

The high rate of positive results warrants routine toxicology testing. The imputability of identified molecules is complicated by the presence of other known risk factors for SUID.

Murine Electrophysiological Models of Cardiac Arrhythmogenesis

Cardiac arrhythmias can follow disruption of the normal cellular electrophysiological processes underlying excitable activity and their tissue propagation as coherent wavefronts from the primary sinoatrial node pacemaker, through the atria, conducting structures and ventricular myocardium. These physiological events are driven by interacting, voltage-dependent, processes of activation, inactivation, and recovery in the ion channels present in cardiomyocyte membranes. Generation and conduction of these events are further modulated by intracellular Ca2+ homeostasis, and metabolic and structural change. This review describes experimental studies on murine models for known clinical arrhythmic conditions in which these mechanisms were modified by genetic, physiological, or pharmacological manipulation. These exemplars yielded molecular, physiological, and structural phenotypes often directly translatable to their corresponding clinical conditions, which could be investigated at the molecular, cellular, tissue, organ, and whole animal levels. Arrhythmogenesis could be explored during normal pacing activity, regular stimulation, following imposed extra-stimuli, or during progressively incremented steady pacing frequencies. Arrhythmic substrate was identified with temporal and spatial functional heterogeneities predisposing to reentrant excitation phenomena. These could arise from abnormalities in cardiac pacing function, tissue electrical connectivity, and cellular excitation and recovery. Triggering events during or following recovery from action potential excitation could thereby lead to sustained arrhythmia. These surface membrane processes were modified by alterations in cellular Ca2+ homeostasis and energetics, as well as cellular and tissue structural change. Study of murine systems thus offers major insights into both our understanding of normal cardiac activity and its propagation, and their relationship to mechanisms generating clinical arrhythmias.

Testing for Infectious Diseases in Sudden Unexpected Infant Death: A Survey of Medical Examiner and Coroner Offices in the United States

OBJECTIVES

To determine interoffice variability in routinely performed sudden unexpected infant death (SUID) postmortem studies for infection and to assess availability and perceived utility of various tests of infectious diseases.

STUDY DESIGN

Online surveys were sent to all 154 offices of US medical examiners and coroners serving populations >300,000 people. Surveys included a set of potential laboratory tests for infectious disease. Respondents were asked to select which tests were available in their offices, and which tests were performed routinely in SUIDs vs which tests should be performed routinely.

RESULTS

Of the 45 complete responses, 4.4% did not routinely perform histology, 8.9% did not routinely perform viral studies (ie, culture or molecular diagnostics), 22.2% did not routinely perform blood cultures, 26.7% did not routinely perform lung bacterial cultures, and 44.4% did not routinely perform cerebrospinal fluid cultures.

CONCLUSIONS

Our findings suggest that there is considerable interoffice variability with testing for infectious diseases in SUIDs. This appeared to be largely the result of a perceived lack of testing utility rather than a lack of test availability. Evidence-based practice guidelines regarding the interpretation of microbial testing results, as well as common testing protocols/algorithms, may lead to more accurate and standardized data, thus improving SUID investigation and surveillance.

The role of ion channelopathies in sudden cardiac death: implications for clinical practice

Sudden cardiac death (SCD) following ventricular tachyarrhythmias constitutes an important clinical cause of mortality; 4% of cases may involve ion channel-mediated cellular excitation in structurally normal hearts. Alterations in such processes could disturb action potential conduction, depolarization/ repolarization gradients, or Ca(2+) homeostasis with potential arrhythmogenic consequences. Although SCD may be the first presentation of arrhythmic syndromes, patients may present to the general physician with symptoms of palpitations or hemodynamic compromise, including dizziness, seizure, or syncope, particularly following exertion. In all inherited cardiac death syndromes, first-degree relatives should be referred to a cardiologist and should undergo testing appropriate for the condition. While management of patients at risk of SCD largely centers on risk stratification and, if necessary, insertion of an implantable cardioverter-defibrillator, there are a number of other, pharmacological, treatments being developed. Furthermore, as the genetic basis of these diseases becomes established, genetic testing will form an increasingly important part of diagnosis, and gene-specific therapy is an area under investigation. This article bridges the gap between molecular medicine and clinical practice by reviewing recent developments in the pathophysiological understanding of SCD, and their implications for the management of patients with these complex diseases.

Novel mutations in the KCND3-encoded Kv4.3 K+ channel associated with autopsy-negative sudden unexplained death

Heritable arrhythmia syndromes, including Brugada syndrome (BrS) and idiopathic ventricular fibrillation (IVF), may serve as the pathogenic basis for autopsy-negative sudden unexplained death (SUD) and sudden infant death syndrome (SIDS). Emerging evidence has linked perturbations in the transient outward current (I(to) ) conducted by the KCND3-encoded Kv4.3 pore-forming α-subunit to BrS or IVF. However, the contribution of KCND3 mutations to autopsy-negative SUD/SIDS is unknown. To investigate the potential association between KCND3 and SUD/SIDS, mutational analysis of KCND3 was conducted in 123 SUDS and 292 SIDS victims using polymerase chain reaction, denaturing high-performance liquid chromatography, and direct sequencing. Overall, one SIDS case (<1.0%) and two SUDS cases (1.6%) harbored potentially pathogenic mutations in KCND3. The novel p.Val392Ile, p.Ser530Pro, and p.Gly600Arg mutations involved highly conserved residues and were absent in 1,560 reference alleles. Although the SIDS-associated p.Ser530Pro mutation demonstrated a wild-type (WT) electrophysiological phenotype when heterologously expressed, the SUDS-associated p.Val392Ile and p.Gly600Arg mutations significantly increased peak current density at +40 mV in comparison with WT by 100.4% (P < 0.05) and 50.4% (P < 0.05), respectively. p.Val392Ile also slowed recovery from inactivation 3.6-fold, indicating a mixed electrophysiological phenotype. This is the first report indicating that KCND3 may serve as a rare genetic substrate in the pathogenesis of SUDS but not SIDS cases.

The molecular autopsy: should the evaluation continue after the funeral?

Sudden cardiac death (SCD) is one of the most common causes of death in developed countries, with most SCDs involving the elderly, and structural heart disease evident at autopsy. Each year, however, thousands of sudden deaths involving individuals younger than 35 years of age remain unexplained after a comprehensive medicolegal investigation that includes an autopsy. In fact, several epidemiologic studies have estimated that at least 3% and up to 53% of sudden deaths involving previously healthy children, adolescents, and young adults show no morphologic abnormalities identifiable at autopsy. Cardiac channelopathies associated with structurally normal hearts such as long QT syndrome (LQTS), catecholaminergic polymorphic ventricular tachycardia (CPVT), and Brugada syndrome (BrS) yield no evidence to be found at autopsy, leaving coroners, medical examiners, and forensic pathologists only to speculate that a lethal arrhythmia might lie at the heart of a sudden unexplained death (SUD). In cases of autopsy-negative SUD, continued investigation through either a cardiologic and genetic evaluation of first- or second-degree relatives or a molecular autopsy may elucidate the underlying mechanism contributing to the sudden death and allow for identification of living family members with the pathogenic substrate that renders them vulnerable, with an increased risk for cardiac events including syncope, cardiac arrest, and sudden death.

[Problems and advantages of autopsy in the case of out-of-hospital childhood death: report of 2 cases]

In France, the number of deaths remains high in the pediatric population. These deaths are rarely subject to a scientific or forensic autopsy. However, this medical act appears necessary to answer the many private and public questions (public health, prevention, judicial, or even institutional) that can arise. Two pediatric clinical observations raising these questions in the context of a household accident are presented. In the first one, the death led to the establishment of a forensic obstacle to the burial and a forensic autopsy. The autopsy results provided answers, both to the relatives and to the court. The second concerns a deceased child managed within the protocol for sudden infant death syndrome. The autopsy was not authorized by the parents and no answer on the causes of death could be determined. These 2 observations underline the importance and utility of this medical act.

Cardiac channelopathies and sudden infant death syndrome

Sudden infant death syndrome (SIDS) is always a devastating and unexpected occurrence. SIDS is the leading cause of death in the first 6 months after birth in the industrialized world. Since the discovery in 1998 of long QT syndrome as an underlying substrate for SIDS, around 10-20% of SIDS cases have been proposed as being caused by genetic variants in either ion channel or ion channel-associated proteins. Until now, 10 cardiac channelopathy susceptibility genes have been found to be implicated in the pathogenesis of SIDS. Four of the genes encode cardiac ion channel α-subunits, 3 genes encode ion channel β-subunits, and 3 genes encode other channel-interacting proteins. All 10 genes have been associated with primary electrical heart diseases. SIDS may hereby be the initial symptom of rare primary electric channelopathies such as long QT, short QT and Brugada syndrome, as well as catecholaminergic polymorphic ventricular tachycardia. In this review we describe the functional role of sodium, potassium and calcium channels in propagation, depolarization and repolarization in the context of the 4 arrhythmogenic diseases reported to be associated with SIDS. Lastly, the possibility of postmortem genetic testing and potential recommendations on how to deal with family members are discussed.

Investigating sudden unexpected death in infancy and early childhood

Sudden unexpected death is one of the most frequent ways of dying in the first year of life after the neonatal period. It is however, much less frequent after the first birthday. Investigations into the cause of death are very important, for a significant proportion of these sudden deaths can be explained only after a thorough investigation. Of the causes identified, infection is the most frequent cause; metabolic disorders and cardiovascular diseases play a role as well, although the proportion of cases is much smaller. There is now evidence that cardiac channel gene mutations also play an important role; however, identification of these conditions relies on costly testing that is not readily or widely available. The physician's role as primary care provider is critical in ensuring that families understand the results of the investigation into their child's death. It is important that everything be done to identify the cause of death so that no such tragedy recurs in the same family.

Genomic risk factors in sudden infant death syndrome

Sudden infant death syndrome (SIDS) is a major contributor to postneonatal infant death, and is the third leading cause of infant mortality in the USA. While public health efforts have reduced these deaths in recent years, the pathogenesis of SIDS remains unclear. Epidemiological data on SIDS-related deaths have suggested genetic factors, and many studies have attempted to identify SIDS-associated genes. This has resulted in a large body of literature implicating various genes and their encoded proteins and signaling pathways in numerous cohorts of various sizes and ethnicities. This review has undertaken a systematic evaluation of these studies, identifying the pathways that have been implicated in these studies, including central nervous system pathways, cardiac channelopathies, immune dysfunction, metabolism/energy pathways, and nicotine response. This review also explores how new genomic techniques will aid in advancing our knowledge of the genomic risk factors associated with SIDS, including SNPs and copy number variation. Last, this review explores how the current information can be applied to aid in our assessment of the at risk infant population.

Virological investigations in sudden unexpected deaths in infancy (SUDI)

Previous studies have implicated viral infections in the pathogenesis of sudden unexpected death in infancy (SUDI), and routine virological investigations are recommended by current SUDI autopsy protocols. The aim of this study is to determine the role of post-mortem virology in establishing a cause of death. A retrospective review of 546 SUDI autopsies was carried out as part of a larger series of >1,500 consecutive paediatric autopsies performed over a 10-year period, 1996-2005, in a single specialist centre. Virological tests were performed as part of the post-mortem examination in 490 (90%) of the 546 SUDI autopsies, comprising 4,639 individual virological tests, of which 79% were performed on lung tissue samples. Diagnostic methods included immunofluorescence assays (using a routine respiratory virus panel; 98% of cases), cell culture (61%), rapid culture techniques such as the DEAFF test for CMV (55%), PCR (13%), electron microscopy (10%), and others. Virus was identified in only 18 cases (4%), viz. five cases of enterovirus, four of RSV, three of HSV and CMV, and one each of adenovirus, influenza virus and HIV. In seven of the 18 cases the death was classified as due to viral infection, whilst of the remaining 11 cases, death was due to bacterial infection in five, a non-infective cause in one and unexplained in five. Virus was identified in 33% of deaths due to probable viral infections, but also in 6% of SUDI due to bacterial infections, and in 2% of SUDI due to known non-infective causes and unexplained SUDI. When predominantly using immunofluorescence, virus is identified in only a small proportion of SUDI autopsies, resulting in a contribution to the final cause of death in <2% of SUDI post-mortem examinations. Routine post-mortem virological analysis by means of an immunofluorescence respiratory virus panel appears to be of limited benefit in SUDI for the purposes of determining cause of death. Application of a broader panel using more sensitive detection techniques may reveal more viruses, although their contribution to the final cause of death requires further exploration.

Infection and sudden unexpected death in infancy: a systematic retrospective case review

BACKGROUND

The cause and mechanism of most cases of sudden unexpected death in infancy (SUDI) remain unknown, despite specialist autopsy examination. We reviewed autopsy results to determine whether infection was a cause of SUDI.

METHODS

We did a systematic retrospective case review of autopsies, done at one specialist centre between 1996 and 2005, of 546 infants (aged 7-365 days) who died suddenly and unexpectedly. Cases of SUDI were categorised as unexplained, explained with histological evidence of bacterial infection, or explained by non-infective causes. Microbial isolates gathered at autopsy were classified as non-pathogens, group 1 pathogens (organisms usually associated with an identifiable focus of infection), or group 2 pathogens (organisms known to cause septicaemia without an obvious focus of infection).

FINDINGS

Of 546 SUDI cases, 39 autopsies were excluded because of viral or pneumocystis infection or secondary bacterial infection after initial collapse and resuscitation. Bacteriological sampling was done in 470 (93%) of the remaining 507 autopsies. 2079 bacteriological samples were taken, of which 571 (27%) were sterile. Positive cultures yielded 2871 separate isolates, 484 (32%) of which showed pure growth and 1024 (68%) mixed growth. Significantly more isolates from infants whose deaths were explained by bacterial infection (78/322, 24%) and from those whose death was unexplained (440/2306, 19%) contained group 2 pathogens than did those from infants whose death was explained by a non-infective cause (27/243, 11%; difference 13.1%, 95% CI 6.9-19.2, p<0.0001 vs bacterial infection; and 8.0%, 3.2-11.8, p=0.001 vs unexplained). Significantly more cultures from infants whose deaths were unexplained contained Staphylococcus aureus (262/1628, 16%) or Escherichia coli (93/1628; 6%) than did those from infants whose deaths were of non-infective cause (S aureus: 19/211, 9%; difference 7.1%, 95% CI 2.2-10.8, p=0.005; E coli: 3/211, 1%, difference 4.3%, 1.5-5.9, p=0.003).

INTERPRETATION

Although many post-mortem bacteriological cultures in SUDI yield organisms, most seem to be unrelated to the cause of death. The high rate of detection of group 2 pathogens, particularly S aureus and E coli, in otherwise unexplained cases of SUDI suggests that these bacteria could be associated with this condition.

Molecular and functional characterization of novel glycerol-3-phosphate dehydrogenase 1 like gene (GPD1-L) mutations in sudden infant death syndrome

BACKGROUND

Autopsy-negative sudden unexplained death, including sudden infant death syndrome, can be caused by cardiac channelopathies such as Brugada syndrome (BrS). Type 1 BrS, caused by mutations in the SCN5A-encoded sodium channel, accounts for approximately 20% of BrS. Recently, a novel mutation in the glycerol-3-phosphate dehydrogenase 1-like gene (GPD1-L) disrupted trafficking of SCN5A in a multigenerational family with BrS. We hypothesized that mutations in GPD1-L may be responsible for some cases of sudden unexplained death/sudden infant death syndrome.

METHODS AND RESULTS

Using denaturing high-performance liquid chromatography and direct DNA sequencing, we performed comprehensive open-reading frame/splice site mutational analysis of GPD1-L on genomic DNA extracted from necropsy tissue of 83 unrelated cases of sudden unexplained death (26 females, 57 males; average age, 14.6+/-10.7 years; range, 1 month to 48 years). A putative, sudden unexplained death-associated GPD1-L missense mutation, E83K, was discovered in a 3-month-old white boy. Further mutational analysis was then performed on genomic DNA derived from a population-based cohort of 221 anonymous cases of sudden infant death syndrome (84 females, 137 males; average age, 3+/-2 months; range, 3 days to 12 months), revealing 2 additional mutations, I124V and R273C, in a 5-week-old white girl and a 1-month-old white boy, respectively. All mutations occurred in highly conserved residues and were absent in 600 reference alleles. Compared with wild-type GPD1-L, GPD1-L mutations coexpressed with SCN5A in heterologous HEK cells produced a significantly reduced sodium current (P<0.01). Adenovirus-mediated gene transfer of the E83K-GPD1-L mutation into neonatal mouse myocytes markedly attenuated the sodium current (P<0.01). These decreases in current density are consistent with sodium channel loss-of-function diseases like BrS.

CONCLUSIONS

The present study is the first to report mutations in GPD1-L as a pathogenic cause for a small subset of sudden infant death syndrome via a secondary loss-of-function mechanism whereby perturbations in GPD1-L precipitate a marked decrease in the peak sodium current and a potentially lethal BrS-like proarrhythmic substrate.

Investigation of unexplained infant deaths in Jerusalem, Israel 1996-2003

BACKGROUND

Sudden infant death syndrome (SIDS) is a diagnosis of exclusion that may be assigned only after investigations including a forensic autopsy are performed to exclude possible organic and environmental causes of death. Israeli society is influenced by the Jewish and Islamic faiths, which permit autopsy only under selected circumstances. Against this background, we carried out a study to determine what examinations are performed to investigate unexplained infant deaths in Jerusalem, Israel.

METHODS

We examined hospital, Ministry of Health and Ministry of Interior records of unexplained infant deaths in the Jerusalem district from the years 1996-2003.

RESULTS

Ninety six cases were identified from all sources. Forty nine (51%) infants were brought to a hospital at or near the time of death. Studies to determine the cause of death were performed in 54% of cases for which medical records were available for review. These studies included bacterial cultures (44%), skeletal surveys (12%), computerised tomography (3%) and metabolic studies (3%). Only one forensic autopsy was performed, and in no instance was the death site examined by medical personnel. There was a high rate of retrospective review by district health physicians. The most frequently assigned cause of death was SIDS.

CONCLUSIONS

: The capacity of public health officials and forensic pathologists to investigate unexplained infant deaths is strongly affected by the legal, religious and political milieu in which they work. Efforts should be made to develop socially acceptable methods of improving the quality of infant death investigations in Jerusalem.

Radiography after unexpected death in infants and children compared to autopsy

BACKGROUND

Postmortem radiography may reveal skeletal and soft-tissue abnormalities of importance for the diagnosis of cause of death.

OBJECTIVE

To review the radiographs of children under 3 years of age who had died suddenly and unexpectedly. To compare the radiological and autopsy findings evaluating possible differences in children dying of SIDS and of an explainable cause.

MATERIALS AND METHODS

A total of 110 consecutive skeletal surveys performed between 1998 and 2002 were reviewed. All but one were performed before autopsy and comprised AP views of the appendicular and axial skeleton and thorax/abdomen, lateral views of the axial skeleton and thorax, and two oblique views of the ribs. Radiography and autopsy findings were compared.

RESULTS

Causes of death were classified as SIDS/borderline SIDS (n = 52) and non-SIDS (n = 58), with one case of abuse. In 102 infants there were 150 pathological findings, 88 involving the chest, 24 skeletal, and 38 miscellaneous findings. The radiological-pathological agreement was poor concerning pulmonary findings. Skeletal findings were sometimes important for the final diagnosis.

CONCLUSIONS

Radiography revealed many skeletal and soft-tissue findings. Pulmonary pathology was most frequently found, but showed poor agreement with autopsy findings. Recognizing skeletal findings related to abuse is important, as these may escape recognition at autopsy.

Cardiac Sodium Channel Dysfunction in Sudden Infant Death Syndrome

BACKGROUND

Mutations in genes responsible for the congenital long-QT syndrome, especially SCN5A, have been identified in some cases of sudden infant death syndrome. In a large-scale collaborative genetic screen, several SCN5A variants were identified in a Norwegian sudden infant death syndrome cohort (n=201). We present functional characterization of 7 missense variants (S216L, R680H, T1304M, F1486L, V1951L, F2004L, and P2006A) and 1 in-frame deletion allele (delAL586-587) identified by these efforts.

METHODS AND RESULTS

Whole-cell sodium currents were measured in tsA201 cells transiently transfected with recombinant wild-type or mutant SCN5A cDNA (hH1) coexpressed with the human beta1 subunit. All variants exhibited defects in the kinetics and voltage dependence of inactivation. Five variants (S216L, T1304M, F1486L, F2004L, and P2006A) exhibited significantly increased persistent sodium currents (range, 0.5% to 1.7% of peak current) typical of SCN5A mutations associated with long-QT syndrome. These same 5 variants also displayed significant depolarizing shifts in voltage dependence of inactivation (range, 5 to 14 mV) and faster recovery from inactivation, but F1486L uniquely exhibits a depolarizing shift in the conductance-voltage relationship. Three alleles (delAL586-587, R680H, and V1951L) exhibited increased persistent current only under conditions of internal acidosis (R680H) or when expressed in the context of a common splice variant (delQ1077), indicating that they have a latent dysfunctional phenotype.

CONCLUSIONS

Our present results greatly expand the spectrum of functionally characterized SCN5A variants associated with sudden infant death syndrome and provide further biophysical correlates of arrhythmia susceptibility in this syndrome.

Prevalence of long-QT syndrome gene variants in sudden infant death syndrome

BACKGROUND

The hypothesis that some cases of sudden infant death syndrome (SIDS) could be caused by long-QT syndrome (LQTS) has been supported by molecular studies. However, there are inadequate data regarding the true prevalence of mutations in arrhythmia-susceptibility genes among SIDS cases. Given the importance and potential implications of these observations, we performed a study to more accurately quantify the contribution to SIDS of LQTS gene mutations and rare variants.

METHODS AND RESULTS

Molecular screening of 7 genes (KCNQ1, KCNH2, SCN5A, KCNE1, KCNE2, KCNJ2, CAV3) associated with LQTS was performed with denaturing high-performance liquid chromatography and nucleotide sequencing of genomic DNA from 201 cases diagnosed as SIDS according to the Nordic Criteria, and from 182 infant and adult controls. All SIDS and control cases originated from the same regions in Norway. Genetic analysis was blinded to diagnosis. Mutations and rare variants were found in 26 of 201 cases (12.9%). On the basis of their functional effect, however, we considered 8 mutations and 7 rare variants found in 19 of 201 cases as likely contributors to sudden death (9.5%; 95% CI, 5.8 to 14.4%).

CONCLUSIONS

We demonstrated that 9.5% of cases diagnosed as SIDS carry functionally significant genetic variants in LQTS genes. The present study demonstrates that sudden arrhythmic death is an important contributor to SIDS. As these variants likely modify ventricular repolarization and QT interval duration, our results support the debated concept that an ECG would probably identify most infants at risk for sudden death due to LQTS either in infancy or later on in life.

The G protein beta3 subunit 825C allele is associated with sudden infant death due to infection

AIM

To investigate the Gbeta3 subunit C825T polymorphism with regard to sudden unexpected infant death. The reported association between the Gbeta3s protein and increased immune cell function in humans makes this polymorphism highly interesting both with regard to sudden infant death syndrome (SIDS) and deleterious infectious disease.

METHODS

The cases investigated in the present study consist of 250 SIDS cases, 38 cases of sudden unexpected infant death due to infection and 99 living infant controls. Typing of the C825T polymorphism was performed by real-time PCR with allele-specific probes and melting curve analyses.

RESULTS

The cases of infectious death have a higher percentage of both the C allele (p=0.037 compared to the SIDS cases, p=0.022 compared to the controls) and the CC genotype (p=0.05 compared to the SIDS cases, p=0.016 compared to the controls). There were no differences between SIDS cases and controls.

CONCLUSION

The observed association between the 825C allele and infectious death may indicate that the presence of the 825T allele exerts a protective effect towards serious infection, possibly through enhanced G protein signalling. The C allele, on the other hand, appears to represent a disadvantage in this regard.

Virological analysis in the diagnosis of sudden children death: A medico-legal approach

Infections are considered to be an important cause of unexpected death in children. It has also been assumed that respiratory viruses are involved in the genesis of sudden infant death syndrome (SIDS). The Spanish National Institute of Toxicology and Forensic Sciences act as the forensic reference centre for Spain. We analyse the experience of this centre in the virological study of 64 cases of sudden children death where viral serology, virological cultures, herpesviruses polymerase chain reaction (PCR) and electron microscopy were performed. According to pathological findings, death could only be attributed to an adenovirus infection in one amygdalitis with upper airways stenosis and asphyxia. Human herpes virus 6 (HHV-6) was detected by PCR in one case with pathological findings characteristic of SIDS. Recent infection by respiratory syncytial virus (RSV), Epstein-Barr virus (EBV) and cytomegalovirus (CMV) were also detected. Meanwhile, 85.9% of the cases yielded negative viral results. Twenty-eight infants were finally categorised as SIDS. Pathological findings of infection were detected in 12 patients despite the negativity of viral analyses. Although viral infection is an uncommon cause of sudden children death, a complete microbiological investigation will help to solve the puzzle of SIDS. Definitive guidelines for microbiological analyses need to be updated whilst new pathogens are discovered or new techniques are implemented in order to clarify unsolved cases.

Sudden infant death syndrome (SIDS)--standardised investigations and classification: recommendations

Sudden infant death syndrome (SIDS) still accounts for considerable numbers of unexpected infant deaths in many countries. While numerous theories have been advanced to explain these events, it is increasingly clear that this group of infant deaths results from the complex interaction of a variety of heritable and idiosyncratic endogenous factors interacting with exogenous factors. This has been elegantly summarised in the "three hit" or "triple risk" model. Contradictions and lack of consistencies in the literature have arisen from diverse autopsy approaches, variable applications of diagnostic criteria and inconsistent use of definitions. An approach to sudden infant death is outlined with discussion of appropriate tissue sampling, ancillary investigations and the use of controls in research projects. Standardisation of infant death investigations with the application of uniform definitions and protocols will ensure optimal investigation of individual cases and enable international comparisons of trends.

The role of molecular autopsy in unexplained sudden cardiac death

PURPOSE OF REVIEW

Sudden cardiac death (SCD) is one of the most common causes of death, with many attributable to cardiac/coronary abnormalities evident at autopsy. A significant number of SCDs, however, particularly in young people, remain unexplained following a medico-legal investigation, including autopsy, and are referred to as autopsy-negative sudden unexplained death (SUD). Due to molecular advances, however, a cardiac channel molecular autopsy may potentially provide a pathogenic basis for SUD and establish cause and manner of death.

RECENT FINDINGS

Over the past decade, five population-based investigations of sudden death in young people elucidated the frequency of and causes responsible for these tragic events. The most inclusive epidemiologic study concluded that nearly 30% of SCDs in young people are autopsy-negative (i.e. SUD) and most likely secondary to cardiac channelopathies. Case reports on the post-mortem molecular diagnosis of cardiac channelopathies through the use of a molecular autopsy have been presented. Recently, a molecular autopsy series of SUD identified pathogenic mutations in long QT syndrome and catecholaminergic polymorphic ventricular tachycardia-associated genes in over one-third of cases. Similar post-mortem cardiac channel genetic testing in a large population-based cohort of sudden infant death syndrome has elucidated mutations in 5-10% of cases.

SUMMARY

With autopsy-negative SUD accounting for a significant number of sudden deaths in young people, a new role for the medical examiner is emerging. An accurate diagnosis, derived from a molecular autopsy, will guide the appropriate initiation of pre-emptive strategies in hopes of preventing future tragedies among those left behind.

Latex agglutination for bacterial antigens and meningococcus PCR: two useful tools in legal sudden deaths

Bacterial infections are considered to be a major cause of sudden deaths. The recognition of infections caused by Neisseria meningitidis is an essential duty of medicolegal offices due to the risk of secondary cases. Since other microorganisms, such as Haemophilus influenzae and Streptococcus pneumoniae, are also involved in infectious sudden deaths, the identification of the pathogen responsible for death is essential in order to establish a positive diagnosis while also preventing secondary meningococcal cases. However, because of the unreliability of culture methods used for autopsy specimens and the fragile nature of the microorganisms, other techniques were used. In this study, the detection of specific antigens of N. meningitidis (serogroups A, B, C, Y and W135), H. influenzae type b, S. pneumoniae and Group B Streptococcus was undertaken in 40 samples from sudden death cases in legal procedures with a latex agglutination test. In addition, a meningococcus polymerase chain reaction (PCR) assay (ctrA, crgA and siaD genes) was also used as a corroboration method for positive N. meningitidis agglutinations. Eleven cases of sudden death were confirmed to be due to meningococcus while one case was confirmed to have been caused by H. influenzae type b fulminant epiglottitis. Rapid laboratory diagnosis of meningococcal infection allowed contacts management and notification to the health authorities. From the point of view of the authors, forensic diagnosis of unascertained deaths should include latex agglutination and meningococcus PCR when a fulminant infection by N. meningitidis or H. influenzae is suspected as well as in deaths where the cause is unclear.

Sudden infant death syndrome and unclassified sudden infant deaths: a definitional and diagnostic approach

The definition of sudden infant death syndrome (SIDS) originally appeared in 1969 and was modified 2 decades later. During the following 15 years, an enormous amount of additional information has emerged, justifying additional refinement of the definition of SIDS to incorporate epidemiologic features, risk factors, pathologic features, and ancillary test findings. An expert panel of pediatric and forensic pathologists and pediatricians considered these issues and developed a new general definition of SIDS for administrative and vital statistics purposes. The new definition was then stratified to facilitate research into sudden infant death. Another category, defined as unclassified sudden infant deaths, was introduced for cases that do not meet the criteria for a diagnosis of SIDS and for which alternative diagnoses of natural or unnatural conditions were equivocal. It is anticipated that these new definitions will be modified in the future to accommodate new understanding of SIDS and sudden infant death.

Sudden infant death syndrome: overview and update

The past decade and a half has seen marked changes in the epidemiology of sudden infant death syndrome (SIDS). The avoidance of certain risk factors such as sleeping prone and cigarette smoke exposure has resulted in the death rate falling dramatically. Careful evaluation of environmental factors and endogenous characteristics has led to a greater understanding of the complexities of the syndrome. The development and implementation of death scene and autopsy protocols has led to standardization in approaches to unexpected infant deaths with increasing diagnoses of accidental asphyxia. Despite these advances, there is still confusion surrounding the diagnosis, with deaths being attributed to SIDS in many communities and countries where death scene investigations and autopsies have not been conducted. The following review provides a brief overview of the historical background, epidemiology, pathology, and pathogenesis of SIDS. Contentious issues concerning the diagnosis and current problems are discussed. Despite calls to abandon the designation, SIDS remains a viable term for infants who die in their sleep with no evidence of accident, inflicted injury, or organic disease after a full investigation has been conducted according to standard guidelines.