Immunohistochemical diagnosis of myocarditis on (infantile) autopsy material: Does it improve the diagnosis?

Sudden death of a 12-year-old boy with severe myocardial fibrosis due to inapparent chronic myocarditis

Sudden death due to unknown cardiac disease in children is an unusual occurrence. An apparently healthy 12-year-old boy without any physical restrictions collapsed suddenly and died despite cardiopulmonary resuscitation. The main autopsy finding was extensive scarring of the myocardium, especially the interventricular septum. This extensive scarring was exceptional for the young age. Histologically, replacement-type fibrosis with patchy lymphomonocytic infiltrate and infiltration by macrophages were observed. The case was diagnosed as chronic myocarditis, which may have progressed to dilated cardiomyopathy with inflammation or inflammatory cardiomyopathy.

Diagnostic challenges and forensic implications in a case of infantile fatal myocarditis

We present the case of a 23-month-old child who died less than 24 h after the onset of cardiac symptoms, despite being admitted to the hospital 72 h earlier. Autopsy revealed no significant macroscopic changes, and histologic examination revealed focal lymphocytic myocarditis with myocyte disruption, diffuse alveolar damage in the exudative phase, and generalized lymphocytic immune activation in other organs. Ante-mortem and post-mortem microbiological exams did not clearly prove a causative role of infectious agents. The peculiarity of this case was characterized by the contrast between the severe clinical features and the mild cardiac histological findings. This discrepancy, coupled with the suspicion of a viral causative role based on both ante-mortem and post-mortem microbiological examinations, presented significant challenges in reaching an etiological diagnosis. This case also confirms that the diagnosis of myocarditis in children cannot be made solely on the basis of histological cut-offs or microbiological results. Using abductive reasoning, various diagnostic hypotheses were formulated and evaluated to arrive at the final diagnosis of fatal myocarditis of viral or post-viral origin. Data from post-mortem examination are often the only source of information that is available to the experts, especially in cases of sudden infant death syndrome. In such cases, the forensic pathologists should accurately evaluate findings that may appear to indicate a different etiology, and, in the absence of clinical or radiological data, interpret post-mortem data in a logically correct manner. The autopsy is the first essential step to evaluate the cause of death and must be integrated with the results of ante- and post-mortem diagnostic tests in a holistic approach, which is crucial to allow forensic pathologists to provide an appropriate and relevant opinion.

Myocarditis in the forensic setting - a review of the literature

Diagnosis of myocarditis as the cause of death at post-mortem is currently determined by a forensic pathologist. There is no systematic method for diagnosis and thus the determination is subject to inter-observer variability and is non-reproducible. Postmortem studies often rely on the clinical method of diagnosis, which is inaccurate. Furthermore, there is no current standardized method of distinguishing between myocarditis as cause of death, and myocardial inflammation as an incidental finding post-mortem. Only a few studies have investigated a method of quantifying this difference using variables such as number of inflammatory cells and presence of myocyte necrosis, however, there are several limitations hindering the reproducibility of this research. This review investigates the current practices and limitations associated with the diagnosis of myocarditis as cause of death in the autopsy setting.

The histopathological spectrum of myocardial inflammation in relation to circumstance of death: a retrospective cohort study in clinical and forensic autopsies

Interpreting a myocardial inflammation as causal, contributory or as of no significance at all in the cause of death can be challenging, especially in cases where other pathologic and/or medico-legal findings are also present. To further evaluate the significance of myocardial inflammation as a cause of death we performed a retrospective cohort study of forensic and clinical autopsy cases. We revised the spectrum of histological inflammatory parameters in the myocardium of 79 adult autopsy cases and related these to the reported cause of death. Myocardial slides were reviewed for the distribution and intensity of inflammatory cell infiltrations, the predominant inflammatory cell type, and the presence of inflammation-associated myocyte injury, fibrosis, edema and hemorrhage. Next, the cases were divided over three groups, based on the reported cause of death. Group 1 (n = 27) consisted of all individuals with an obvious unnatural cause of death. Group 2 (n = 29) included all individuals in which myocarditis was interpreted to be one out of more possible causes of death. Group 3 (n = 23) consisted of all individuals in which myocarditis was reported to be the only significant finding at autopsy, and no other cause of death was found. Systematic application of our histological parameters showed that only a diffuse increase of inflammatory cells could discriminate between an incidental presence of inflammation (Group 1) or a potentially significant one (Groups 2 and 3). No other histological parameter showed significant differences between the groups. Our results suggest that generally used histological parameters are often insufficient to differentiate an incidental myocarditis from a (potentially) significant one.

Complement C9 expression is associated with damaged myocardial cells in pediatric sudden death cases of fulminant myocarditis

Background

Because disease progression is so fast in sudden death of acute fulminant myocarditis, damage of myocardial cells is not evident in routine hematoxylin and eosin staining. To understand damage to myocardial cells and the mechanism of sudden death, immunohistochemical staining was performed for two forensic autopsy cases.

Case presentation

The patients were a healthy 5-year-old girl and 8-year-old boy. They suddenly died within 2 days of appearance of flu-like symptoms. An autopsy showed accumulation of yellowish-clear pericardial fluid containing fibrin deposits, fluid blood in the heart, and congestion of visceral organs. Histologically, minor necrosis or degeneration of myocardial cells with mainly lymphocytic infiltration was observed sometimes in tissue sections. Immunohistochemically, positive complement C9 staining and negative sirtuin 1 staining were found. These findings suggested wide damage of myocardial cells, even in regions with no marked changes in myocardial cells with hematoxylin and eosin staining. These areas corresponded to those with strong accumulation of lymphocytes.

Conclusions

Immunohistochemistry for complement C9 and sirtuin 1 might become a new tool for evaluating damage of myocardial cells of fulminant acute myocarditis.

When is myocarditis indeed the cause of death?

Attribution of death to myocarditis continues to be a controversial issue in forensic pathology, despite the existence of established histopathological criteria as well as complementary investigations. The aim of the study was two-fold: (a) to retrospectively analyse the data obtained from a series of clinical and forensic autopsies in order to assess the number of cases with death attributed to myocarditis, and (b) to reevaluate these cases in order to assess how properly the histopathological diagnosis of myocarditis conformed to established criteria and therefore how accurately these were used on the basis of all postmortem investigation findings to conclude the cause of death. 2474 clinical and forensic autopsies were taken into consideration. Myocarditis was recorded as the official, underlying cause of death in 48 cases. Of those, 8 cases were considered to accurately conform to the histopathological Dallas criteria for the presence of myocarditis and could therefore be classified as cases of fatal myocarditis. In 19 out of 48 cases, description of focal myocarditis was considered to accurately fulfill the histopathological Dallas criteria for the presence of myocarditis. However, data provided by histological analysis and virology testing result reevaluation allowed alternative causes of death to be speculated. In another 21 out of 48 cases, description of focal myocardial inflammation was considered to inaccurately meet the histopathological Dallas criteria for the presence of myocarditis. The findings of our own study appear to be in agreement with previous observations in similar study groups and highlight that since myocarditis may occur in association with many diseases, a great deal of evidence is required before settling on categorical conclusions.