Mesenteric abscess due to Chryseobacterium meningosepticum revealing mesenteric Castleman's disease in an immunocompetent young adult

Mesenteric abscess caused by chryseobacterium meningosepticum is an extremely rare clinical entity, most often found in immunodeficient patients. Castleman disease can manifest as a mesenteric abscess. We here report the case of a 23-year-old patient admitted with generalized acute peritonitis evolving over the last 2 weeks. Abdominal ultrasound showed hypoechoic mass in the intestinal loops, without any further details. During laparotomy, pus was found in the large cavity, a mesenteric abscess was detected in the mesentery of the jejunum 35 cm from the angle of Treitz, without loop perforation and mesenteric adenopathy was found in corresponence with the abscess. Pyoculture isolated chryseobacterium meningosepticum. Histological analysis of mesenteric adenopathy biopsies showed structural anomalies, suggesting hyaline vascular type of Castleman disease. Treatment was based on incision and drainage of the abscess, with pyogenic membrane removal and abdominal cavity lavage with physiological saline solution. Chryseobacterium meningosepticum was only susceptible to Ciprofloxacin. The postoperative course was simple and the patient was discharged on postoperative day 10 after surgery. Clinical and paraclinical follow-up at 12 months did not show any other lymphadenopathy or recurrence. The purpose of this study is to show an extremely rare case of mesenteric abscess due to chryseobacterium meningosepticum associated with isolated mesenteric Castleman disease in an immunocompetent patient and management approaches.