Prolonged Peritoneal Attack: A Rare but Crucial Clinical Presentation of Familial Mediterranean Fever.

Familial Mediterranean fever (FMF) presents with various symptoms. Episodic abdominal pain is one of the most prevalent clinical characteristics of FMF and usually improves within 24-48 hours. We encountered a 50-year-old male patient from Japan who experienced recurrent episodes (several episodes occurring per year) of abdominal pain with fever since his late 20s. The abdominal pain and fever began almost simultaneously in each episode. The abdominal pain typically lasted for 1-2 weeks, while the fever subsided within two days. He remained as immobile as possible because walking worsened the pain. MEditerranean FeVer () gene analysis revealed exon 10 mutations (p.Met694Ile), resulting in an FMF diagnosis. Colchicine therapy effectively controlled the patient's FMF attacks. Although prolonged abdominal pain lasting over a week is an uncommon clinical characteristic of FMF, a proper diagnosis can improve the quality of life and prevent secondary amyloidosis. Therefore, clinicians should be aware of this rare clinical characteristic.