Noriko Ogawa

Acute appendicitis is a common cause of acute abdominal pain but is rare in infants because of anatomical and physiological characteristics that reduce the risk of the luminal obstruction of the appendix. However, when it occurs in infants, it is often difficult to diagnose clinically and may progress rapidly to a fatal outcome. We report a forensic autopsy case of an 11-month-old infant who died 2 d after developing fever and decreased oral intake, without antemortem diagnosis. Autopsy revealed fibrinous ascitic fluid and an edematous, dark-red appendix with fibrin deposits, but no macroscopic luminal obstruction or perforation. Histopathological examination showed diffuse inflammatory cell infiltration and hemorrhage across all layers of the middle and peripheral portions of the appendix, along with lymphoid hyperplasia in the middle portion. Intestinal bacteria were detected in the ascitic fluid. The cause of death was identified as acute appendicitis with subsequent generalized peritonitis. Although luminal obstruction is a common cause of appendicitis, it was not observed macroscopically in this case. However, histopathological findings suggested that lymphoid hyperplasia in the middle portion of the appendix caused luminal narrowing and impaired circulation in the appendiceal wall, triggering appendicitis. This case demonstrates that infantile appendicitis can be fatal even without perforation and highlights the potential role of lymphoid hyperplasia in the pathogenesis. It also underscores the importance of considering appendicitis in the differential diagnosis of infants with nonspecific symptoms and illustrates the value of postmortem histopathological investigation in elucidating the disease mechanism.