Can we use faecal calprotectin to distinguish abdominal pain of familial Mediterranean fever (FMF) from acute appendicitis?

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Dear Editor, We read with great interest the article by Kisacik et al. [1] titled “Accurate diagnosis of acute abdomen in FMF and acute appendicitis patients: how can we use procalcitonin?” They emphasized that commonly used clinical and laboratory parameters are not specific to distinguish FMF from acute appendicitis and suggested that procalcitonin could be a useful test in differentiation. Indeed, the indistinguishability of these two conditions forced some authors to suggest elective appendectomy in FMF patients [2]. Familial Mediterranean fever (FMF) is a hereditary autoinflammatory disease characterized by recurrent attacks of polyserositis usually associated with fever [3]. The most frequent symptom of FMF is abdominal pain, which is a result of peritoneal attack caused by sterile exudate containing fibrin and leukocytes [4]. Acute appendicitis is characterized by a sequence of events starting with initial obstruction of the appendiceal lumen and impaired blood flow, which lead to destruction of the local epithelium barrier, bacterial invasion, and subsequent leukocyte infiltration [5]. We hypothesize that faecal calprotectin, a new marker of intestinal inflammation, may also be used to distinguish abdominal pain of FMF from acute appendicitis. Calprotectin is a protein that comprises approximately half of the cytosolic protein in neutrophils [6]. Recent studies have examined the role of calprotectin in the evaluation of gut inflammation and have found that it can accurately distinguish active inflammatory bowel disease from other causes of bowel dysfunction [7, 8]. Close correlation between faecal calprotectin concentration and faecal leukocyte excretion has been described [9]. This protein is mostly released as a result of cell disruption or death. Mucosal epithelial cells have also been shown to express calprotectin in their cytoplasm constitutively. Therefore, increased shedding of epithelial cells could contribute to the increased levels found in stool [10]. We suggest that faecal calprotectin concentrations will increase in acute appendicitis, since there is leukocyte infiltration and shedding of epithelial cells to the intestinal tract during this inflammatory process. Nevertheless, during an abdominal attack of FMF, leukocyte migration will take place, and this migration will be towards the peritoneum and not to the intestinal lumen. Clin Rheumatol (2009) 28:239–240 DOI 10.1007/s10067-008-1041-7