BACKGROUND: Animal bites are typically harmless, but in rare cases infections 
introduced by such bites can be fatal. Capnocytophaga canimorsus, found in the 
normal oral flora of dogs, has the potential to cause conditions ranging from 
minor cellulitis to fatal sepsis. The tendency of C. canimorsus infections to 
present with varied symptoms, the organism's fastidious nature, and difficulty 
of culturing make this a challenging diagnosis. Rarely, bacterial cytotoxins 
such as those produced by C. canimorsus may act as causative agents of TTP, 
further complicating the diagnosis. Early recognition is crucial for survival, 
and the variability of presentation must be appreciated. We present the first 
known case of C. canimorsus infection resulting in TTP that initially presented 
as splenic infarction.
CASE PRESENTATION: 72-year-old Caucasian male presented with a four-day history 
of abdominal pain, nausea, vomiting, diarrhea, and intermittent confusion. On 
presentation, vital signs were stable and the patient was afebrile. Physical 
examination was unremarkable apart from petechiae on the inner left thigh, and 
extreme diffuse abdominal pain to palpation and percussion along with positive 
rebound tenderness. Initial investigations revealed leukocytosis with left shift 
and thrombocytopenia, but normal liver enzymes, cardiac enzymes, lipase, INR and 
PTT. Abdominal CT demonstrated a non-enhancing spleen and hemoperitoneum, 
suggesting complete splenic infarction. Although the patient remained afebrile, 
he continued deteriorating over the next two days with worsening 
thrombocytopenia. After becoming febrile, he developed microangiopathic 
hemolytic anemia and hemodynamic instability, and soon after was intubated due 
to hypoxic respiratory failure and decreased consciousness. Plasma exchange was 
initiated but subsequently stopped when positive blood cultures grew a 
gram-negative organism. The patient progressively improved following therapy 
with piperacillin-tazobactam, which was switched to imipenem, then meropenem 
when Capnocytophaga was identified.
CONCLUSIONS: There is a common misconception amongst practitioners that the 
presence of systemic infection excludes the possibility of TTP and vice versa. 
This case emphasizes that TTP may occur secondary to a systemic infection, 
thereby allowing the two processes to coexist. It is important to maintain a 
wide differential when considering the diagnosis of either TTP or C. canimorsus 
infection since delays in treatment may have fatal consequences.