Streptococcus pneumoniae primary peritonitis mimicking acute appendicitis in an immunocompetent patient: a case report and review of the literature

INTRODUCTION: Primary peritonitis without an identifiable intra-abdominal source is extremely rare in healthy individuals; it is commonly seen in cases of nephrotic syndrome, cirrhosis and end-stage liver disease, ascites, immunosuppression, and inflamed peritoneum due to pre-existing autoimmune and oncological conditions. CASE PRESENTATION: We present the case of a 68-year-old Caucasian woman operated on due to acute abdomen with a provisional diagnosis of acute appendicitis. During the operation a small amount of free intra-abdominal fluid was found. Her uterus, ovaries, and fallopian tubes were macroscopically normal. Therefore, with the suspicion of appendicitis, appendectomy was performed. Her blood cultures were negative while peritoneal fluid was positive for capsulated form of Streptococcus pneumoniae. A 30-day follow-up was performed and she was asymptomatic without any sign of infection. DISCUSSION: Streptococcus pneumoniae commonly causes upper respiratory tract infection and cutaneous infections. It very rarely causes gastrointestinal infection and it is very rarely responsible for primary peritonitis and septic shock syndrome. CONCLUSION: Pneumococcal peritonitis has a rare occurrence and represents a clinical challenge because of its subtle and non-specific clinical findings. The interest in our case lays in the relatively rare diagnosis of primary peritonitis mimicking acute appendicitis.