A Fatal Case of Capsular Serovar D of Capnocytophaga canimorsus Infection Following a Dog Bite in a Previously Healthy Adult

We report a rapidly fatal case of <i>Capnocytophaga ​​​​canimorsus</i> septic shock with suspected acute infectious purpura fulminans (AIPF) in a 61-year-old man following a dog bite to the finger. Although he appeared previously healthy, retrospective analysis revealed a markedly small spleen (54 mm in diameter) on computed tomography and Howell-Jolly bodies on a peripheral blood smear, indicating unrecognized functional hyposplenism. He developed systemic symptoms within 48 h and progressed to respiratory failure and refractory shock within 1 h of presentation to the emergency department. The blood smear also demonstrated phagocytosed Gram-negative rods, prompting immediate broad-spectrum antimicrobial therapy and intensive care. However, multiple organ failure progressed, and the patient died on hospital day three. <i>C. canimorsus</i> was identified from blood cultures five days after death; capsular serovar D was confirmed subsequently. This case highlights that <i>C. canimorsus</i> infection can trigger explosive clinical deterioration, particularly when uncommon virulent strains like serovar D infect patients with unrecognized splenic atrophy.