An Autopsy Case of Posterior Pharyngeal Abscesses Caused by Periodontal Bacteria

: A woman in her seventies living alone was found dead on the ﬂoor of her living room. A blue-green swelling was found from her right cheek to her anterior neck and an autopsy was performed. The autopsy revealed subcutaneous abscesses from the right cheek to the anterior neck, posterior pharyngeal abscesses, mediastinal abscesses, pleuritis, and pericarditis. The cause of death was diagnosed as sepsis due to a retropharyngeal abscess caused by extensive severe periodontitis. The presence of a dentist at the autopsy allowed for a rapid diagnosis of periodontal disease, which was the cause of the posterior pharyngeal abscesses and septic shock. Therefore, the participation of a dentist in a forensic autopsy is important not only for personal identiﬁcation but also for the rapid diagnosis of the cause of death. test, Coagulase-negative staphylococci , Streptococcus mitis/oralis , and Pseudomonas alcaligenes were detected. From these results, her cause of death was suspected to be septic shock caused by periodontal disease.


Introduction
A posterior pharyngeal abscess is a pus accumulation in either the posterior pharyngeal space, the dangerous space, or the peri-pharyngeal space between the mucosa of the posterior pharyngeal wall and the cervical spine. Recently, the number of posterior pharyngeal abscesses in infants has decreased sharply due to the development of antibiotics, and on the contrary, the number of posterior pharyngeal abscesses in middle-aged and elderly people has tended to increase [1]. When inflammation spreads to the mediastinum and leads to mediastinitis and mediastinal abscess, the prognosis is poor, with a mortality rate of approximately 40% [2]. Intraoral findings contain a lot of useful information for personal identification. It is possible to identify a person by matching dental treatment marks with the medical records of the clinic [3,4] and to estimate the age and sex of the person from the bite and wear of the teeth [5]. In addition, an oral examination can sometimes help us to identify lifestyle and vocational activity that occurred before death, including eating and smoking habits [6][7][8][9][10].
In the case of decomposed, burned, or skeletal cadavers, the teeth are preserved for a long period, so intraoral findings can be collected [11,12] and play an important role in personal identification. However, intraoral findings are often neglected in the investigation of the cause of death. In our institute, at least one dentist participates in every autopsy. We report a case in which a dentist participated in the autopsy, which led to a quick diagnosis of the cause of death.

Case
One winter afternoon, a 76-year-old woman living alone was found face down and dead in her room. A large blue-green discoloration was found on the right cheek, and the right side of her face was swollen ( Figure 1A). Therefore, a forensic autopsy was performed the next day. The day before she was found, she had canceled an appointment at an osteopath's clinic because of a sore throat.
Forensic. Sci. 2022, 2, FOR PEER REVIEW 2 performed the next day. The day before she was found, she had canceled an appointment at an osteopath's clinic because of a sore throat. During the autopsy, a large amount of white pus was found in the subcutaneous region of the right cheek and the anterior neck, the right sternocleidomastoid muscle, the upper end of the right sternohyoid muscle, and the region from the pharynx to the dorsal surface of the larynx and esophagus (posterior pharyngeal gap) ( Figure 1B). In addition, pleural and pericardial effusions with pus were observed. No apparent airway obstruction was observed. No significant organ damage or lesions were observed. The intraoral examination showed that all the teeth were unstable, gingival recession and gingival redness were present, and the hygienic condition was quite poor ( Figure 1C). The postmortem CT images of the head showed alveolar bone resorption in the entire jaw, especially around the right maxillary canine and the left mandibular central incisor ( Figure 2). Postmortem blood examinations showed white blood cell count: 109 × 10 2 /µL, CRP: 40.15 mg/dL, and procalcitonin: 15.0 ng/mL. There is no standard value for post-mortem biochemical tests, so this is just a reference value. Histopathologic examination revealed microthrombi within the glomeruli of the right kidney ( Figure 3A). Many neutrophils were found in the red splenic cord of the spleen ( Figure 3B). In addition, microthrombi were found in various veins throughout the body. In the blood culture test, Coagulase-negative staphylococci, Streptococcus mitis/oralis, and Pseudomonas alcaligenes were detected. From these results, her cause of death was suspected to be septic shock caused by periodontal disease. During the autopsy, a large amount of white pus was found in the subcutaneous region of the right cheek and the anterior neck, the right sternocleidomastoid muscle, the upper end of the right sternohyoid muscle, and the region from the pharynx to the dorsal surface of the larynx and esophagus (posterior pharyngeal gap) ( Figure 1B). In addition, pleural and pericardial effusions with pus were observed. No apparent airway obstruction was observed. No significant organ damage or lesions were observed. The intraoral examination showed that all the teeth were unstable, gingival recession and gingival redness were present, and the hygienic condition was quite poor ( Figure 1C). The postmortem CT images of the head showed alveolar bone resorption in the entire jaw, especially around the right maxillary canine and the left mandibular central incisor ( Figure 2). Post-mortem blood examinations showed white blood cell count: 109 × 10 2 /µL, CRP: 40.15 mg/dL, and procalcitonin: 15.0 ng/mL. There is no standard value for post-mortem biochemical tests, so this is just a reference value. Histopathologic examination revealed microthrombi within the glomeruli of the right kidney ( Figure 3A). Many neutrophils were found in the red splenic cord of the spleen ( Figure 3B). In addition, microthrombi were found in various veins throughout the body. In the blood culture test, Coagulase-negative staphylococci, Streptococcus mitis/oralis, and Pseudomonas alcaligenes were detected. From these results, her cause of death was suspected to be septic shock caused by periodontal disease.
performed the next day. The day before she was found, she had canceled an appointmen at an osteopath's clinic because of a sore throat. During the autopsy, a large amount of white pus was found in the subcutaneou region of the right cheek and the anterior neck, the right sternocleidomastoid muscle, th upper end of the right sternohyoid muscle, and the region from the pharynx to the dorsa surface of the larynx and esophagus (posterior pharyngeal gap) ( Figure 1B). In addition pleural and pericardial effusions with pus were observed. No apparent airway obstruc tion was observed. No significant organ damage or lesions were observed. The intraora examination showed that all the teeth were unstable, gingival recession and gingival red ness were present, and the hygienic condition was quite poor ( Figure 1C). The postmor tem CT images of the head showed alveolar bone resorption in the entire jaw, especially around the right maxillary canine and the left mandibular central incisor (Figure 2). Post mortem blood examinations showed white blood cell count: 109 × 10 2 /µL, CRP: 40.1 mg/dL, and procalcitonin: 15.0 ng/mL. There is no standard value for post-mortem bio chemical tests, so this is just a reference value. Histopathologic examination revealed mi crothrombi within the glomeruli of the right kidney ( Figure 3A). Many neutrophils wer found in the red splenic cord of the spleen ( Figure 3B). In addition, microthrombi wer found in various veins throughout the body. In the blood culture test, Coagulase-negativ staphylococci, Streptococcus mitis/oralis, and Pseudomonas alcaligenes were detected. From these results, her cause of death was suspected to be septic shock caused by periodonta disease.   Subcutaneous abscesses from the right cheek to the anterior neck, posterior pharyn geal abscesses, mediastinal abscesses, pleuritis, and pericarditis were observed, suggest ing that she may have died of sepsis caused by these lesions.
Subsequent bacterial examination of pus from the subcutaneous region of the ante rior neck and thoracic cavity revealed Prevotella intermedia, Peptostreptococcus sp., Fusobac terium nucleatum, and Eggerthia catenaformis, and the diagnosis was confirmed.
The bacterial species detected in these subcutaneous and mediastinal abscesses were also known as periodontal-associated bacteria and were considered to have been caused by the severe periodontal disease she had. However, the postmortem interval was abou 48 h, and the bacteria present may have grown after death.

Discussion
There have been several reports of deaths due to posterior pharyngeal abscesse caused by periodontal bacteria [13][14][15]. In addition to posterior pharyngeal abscesses spontaneous posterior pharyngeal hematoma and pharyngeal cancer have been reported as rare causes of death due to upper airway obstruction [16,17]. Periodontal bacteria hav been reported to cause angina pectoris, myocardial infarction, cerebral infarction, and as piration pneumonia [18][19][20][21]. In this case, no airway obstruction was observed from th posterior pharyngeal abscesses, and post-mortem blood culture test results showed ora bacteria. Normally, oral bacteria is not detected in the postmortem blood examination suggesting that oral bacteria had invaded through the periodontal disease into the sys temic blood and caused posterior pharyngeal abscesses, finally causing death by septi shock. It is very useful for dentists to diagnose the severity of diseases in the facial region that may be the cause of death. The participation of dentists in forensic autopsies make it possible to quickly diagnose the cause of death, as seen in our case. However, despit the surplus of dentists in Japan, the number of forensic dentists is very small, and most o them work in single dental colleges. They have little cooperation with medical facultie that perform autopsies, and they are very rarely involved in autopsies. The dentist is usu ally called upon to assist with personal identification only after the autopsy.

Conclusions
Forensic pathologists must be aware of the need for evaluation by specialists, includ ing dentists, and must ensure that they have the means to refer to specialists when neces sary. On the other hand, we strongly insist that dentists actively participate not only in personal identification, but also in the investigation of cause of death. Subcutaneous abscesses from the right cheek to the anterior neck, posterior pharyngeal abscesses, mediastinal abscesses, pleuritis, and pericarditis were observed, suggesting that she may have died of sepsis caused by these lesions.
Subsequent bacterial examination of pus from the subcutaneous region of the anterior neck and thoracic cavity revealed Prevotella intermedia, Peptostreptococcus sp., Fusobacterium nucleatum, and Eggerthia catenaformis, and the diagnosis was confirmed.
The bacterial species detected in these subcutaneous and mediastinal abscesses were also known as periodontal-associated bacteria and were considered to have been caused by the severe periodontal disease she had. However, the postmortem interval was about 48 h, and the bacteria present may have grown after death.

Discussion
There have been several reports of deaths due to posterior pharyngeal abscesses caused by periodontal bacteria [13][14][15]. In addition to posterior pharyngeal abscesses, spontaneous posterior pharyngeal hematoma and pharyngeal cancer have been reported as rare causes of death due to upper airway obstruction [16,17]. Periodontal bacteria have been reported to cause angina pectoris, myocardial infarction, cerebral infarction, and aspiration pneumonia [18][19][20][21]. In this case, no airway obstruction was observed from the posterior pharyngeal abscesses, and post-mortem blood culture test results showed oral bacteria. Normally, oral bacteria is not detected in the postmortem blood examination, suggesting that oral bacteria had invaded through the periodontal disease into the systemic blood and caused posterior pharyngeal abscesses, finally causing death by septic shock. It is very useful for dentists to diagnose the severity of diseases in the facial region that may be the cause of death. The participation of dentists in forensic autopsies makes it possible to quickly diagnose the cause of death, as seen in our case. However, despite the surplus of dentists in Japan, the number of forensic dentists is very small, and most of them work in single dental colleges. They have little cooperation with medical faculties that perform autopsies, and they are very rarely involved in autopsies. The dentist is usually called upon to assist with personal identification only after the autopsy.

Conclusions
Forensic pathologists must be aware of the need for evaluation by specialists, including dentists, and must ensure that they have the means to refer to specialists when necessary. On the other hand, we strongly insist that dentists actively participate not only in personal identification, but also in the investigation of cause of death.

Impact Statement
This case illustrates the importance of the dentist's participation in the autopsy, as the dentist was able to evaluate the oral disease, and the cause of death was thus determined. Informed Consent Statement: Informed consent was not required because this case was a judicial autopsy.