[Sudden unexpected natural death from a viewpoint of forensic pathology]

Sudden unexpected natural death (SUND) has several characteristics, such as unknown clinical history, very short course to death, evidence of trauma, interference of postmortem changes and social implications of diagnosis. From these points, SUND involves important challenges in forensic pathology. Presented here are the highlights of our SUND studies which allow scientific speculation into the antemortem pathophysiological course to death and a subsequent accurate diagnosis of the cause of death in SUND cases. 1. Forensic problems of SUND of unknown etiology 1) Do sudden infant death syndrome (SIDS) studies continue endlessly? In Japan there are many cases of sudden unexpected infant death (SUID) which were regarded as SIDS, often without postmortem examination. Pure SIDS should be a diagnosis of exclusion under thorough postmortem examination. Additionally, many SIDS studies have focused on pathogenesis of pure SIDS based on the analysis of so-called SIDS cases described above. In this sense, SIDS studies may continue forever. To clarify whether SIDS is an onion type, that is a heterogeneous disease entity, or bamboo shoot type, a single disease entity with a single cause, it is more vital to accurately search autopsy findings to exclude the cause of death, rather than to study pathogenesis of SIDS. Thereafter, pure SIDS will be carved in relief and we could study the pathogenesis, if it remains in the future. Present in 40% of our SUID cases examined was the existence of viral infection as a cause of death. 2) Pokkuri disease It has long been believed that the main branches of coronary arteries in Pokkuri-disease cases are macroscopically hypoplastic and cause sudden cardiac death. However, our two-dimensional morphometric analysis of the main branches, such as wall thickness, degree of stenosis, lumen area, area within internal elastic lamina, showed no significant differences between Pokkuri-disease cases and age and sex-matched control cases. 2. Information for grasping antemortem pathophysiological state in SUND cases 1) Standardization of the degree of cardiac hypertrophy based on heart weight. In the course of our preliminary examination, we found that heart weight correlates significantly with body length and weight. Therefore, we tried to standardize the range of normotrophy, hypertrophy and hypoplasia/atrophy of the heart based on the correlation between heart weight and body type index calculated by body length and weight (Broca's index). 2) Evaluation of the clinical laboratory data in cadaveric blood. We examined 32 clinical laboratory parameters in cadaveric blood samples obtained from 192 autopsy cases. Behaviour of the laboratory parameters in cadaveric blood in relation to postmortem interval was divided into four types: increased, decreased, no particular tendency and remaining between upper and lower normal value. Parameters included in the last type, which is a useful tool for speculation of antemortem pathophysiology were T-Bil, TTT, ZTT, BUN, Cre, UA, alpha 1- and beta 2-microglobin, T-Chol, GHA1c, TP, A/G, Hb and Hct. A case was demonstrated in which values of clinical laboratory parameters in agonar stage were the same as in cadaveric blood obtained at autopsy. This indicates that caution is necessary in evaluating clinical laboratory data in agonar patients in the emergency room. 3) Diagnostic evaluation of immunohistochemical myoglobin staining in the kidney In order to evaluate the diagnostic value of myoglobin (Mb) staining in the kidney in medicolegal autopsy cases, Mb staining was carried out on the kidney sections of 141 victims, including 59 natural and 82 unnatural deaths. At the same time, Serum and Urine GFR parameters were measured and systemic histological changes were observed on some sections of each kidney. The incidence of Mb positive cases was 74.6% in unnatural, and 25.4% in natural death, indicating the importance of nontraumatic rhabdomyolysis in natural death cases.