Rare Case of Capnocytophaga Canimorsus Infection Causing Overwhelming Sepsis Initially Thought to Be Hemophagocytic Lymphohistiocytosis

Abstract

INTRODUCTION: Capnocytophaga species are a collection of fusiform gram-negative rods that are considered part of the oral commensal flora. They are opportunistic pathogens and most often cause periodontal infections. In immunocompromised patients, C. Canimorsus can be transmitted via dog bite and causes severe sepsis, with death as a frequent outcome. CASE PRESENTATION:We present a case of a 36-year-old woman with no known past medical history who presented to outside hospital with acute onset of fevers and malaise as well as subacute polyarthralgia, malar rash, and fatigue. Labs showed severe leukopenia with concern for acute myeloid leukemia prompting her transfer to our institution. Upon arrival, peripheral smear showed toxic appearing neutrophils, thrombocytopenia, and no evidence of blasts with overall smear findings consistent with severe sepsis. Patient was anuric with labs consistent with D.I.C. She had a purpuric rash affecting bilateral distal upper and lower extremities consistent with purpura fulminans. She was started on vancomycin and piperacillin / tazobactam with blood, urine and sputum cultures obtained. On admission day 3 she was intubated for acute hypoxic respiratory failure secondary to volume overload from acute renal failure. Given the high acuity and rapid progression of her illness a broad differential was entertained. Hematology, nephrology, rheumatology, and infectious disease were consulted for aid in diagnosis and treatment. Initially there was higher index of suspicion for hemophagocytic lymphohistiocytosis (HLH) given the cytopenias, ferritin > 5000, and acute inflammatory syndrome. Soluble IL-2 receptor levels were sent and found to be elevated, however not high enough to be specific for HLH. After further history taking, it was revealed that she had sustained a bite from her pet dog with puncture wound on her fingers 3 days before falling ill. Dermatology performed tissue biopsy which did reveal bacterial tissue growth. Pathologist review of the peripheral blood smear revealed the presence of intra-cellular gram-negative organisms in several of the patient's neutrophils consistent with C. canimorsus infection. With supportive care, initiation of RRT and antibiotics she improved. She did require amputation of several digits on her hands and feet and had a prolonged course while inpatient, but eventually was discharged from the hospital. DISCUSSION: Risk factors for severe infection with C. canimorsus include asplenia, alcoholism, and immune compromise. Further discussion revealed that she had been drinking close to 8 beers per day prior to her bite, which is her most likely predisposing factor for this presentation.CONCLUSIONS: This case underlies the importance of maintaining a broad differential and frequently revisiting the differential, history, and exam as more information becomes available.