en Reumatology Reumatology case report case report <span style="font-size:14px;"><span style="font-family:times new roman;"><span style="color:#0000FF;"><strong><em>Background</em></strong><em>:</em></span> Periodic fever, aphthous stomatitis, pharyngitis, and adenitis syndrome (PFAPA) is an auto-immune based disease known as a syndrome for pediatrics which typically occurs in children &le; 5 years of age, but in 2008, for the first time, one adult case of this disease was reported.<br> <span style="color:#0000FF;"><strong><em>Case Presentation</em></strong><em>:</em></span> Our case, a 19 year-old young man who is the first adult-onset PFAPA patient in Iran and was accompanied by splenomegaly. Since March 2017, the patient suffered from periodic febrile attacks (39-40 &deg;C). During these fever attacks, the patient had many aphthous ulcers in his mouth, swollen glands in his neck and sore in the back of the throat. The patient was admitted to a hospital in Tehran during a severe fever attack due to weakness, lethargy, high-temperature and slight abdominal pain in the left upper quadrant (LUQ) area. Abdominal<a href="https://www.radiologyinfo.org/en/info.cfm?pg=genus"> sonography</a> was done and spleen size was larger than normal and was determined to be 32&times;140 mm (splenomegaly). All data were collected from a reliable governmental laboratory in Tehran.<br> <span style="color:#0000FF;"><strong><em>Conclusion</em></strong><em>:</em></span> Following the rejection of the causes of other diseases, according to the patient&#39;s symptoms, the diagnosis of adult-onset PFAPA was given to the patient and the patient was cured with one dose of long-acting Betamethasone ampoule 1ml intravenous&nbsp;at the onset of fever attacks. The disease has remitted after injection of this medicine at the onset of each attack rapidly after about 2-3 hours. Also, Montelukast has been given to the patient and we saw his febrile attack intervals increased.</span></span><br> &nbsp; Adult, PFAPA syndrome, Splenomegaly, Iran 231 234 http://caspjim.com/browse.php?a_code=A-10-1122-1&slc_lang=en&sid=1 Shahla Abolghasemi shahlamarmin@yahoo.com 100319475328460016861 100319475328460016861 No Department of Rheumatology, Tehran Medical Sciences Branch, Islamic Azad University, Tehran, Iran Hesam Adin Atashi hero4p@gmail.com 100319475328460016862 100319475328460016862 No Young Researchers and Elite Club, Tehran Medical Sciences Branch, Islamic Azad University, Tehran, Iran Elahe Paydar-Tali Hamid.zaferani73@gmail.com 100319475328460016863 100319475328460016863 No Young Researchers and Elite Club, Tehran Medical Sciences Branch, Islamic Azad University, Tehran, Iran Maedeh Olya maedeh.olya297@gmail.com 100319475328460016864 100319475328460016864 No Young Researchers and Elite Club, Tehran Medical Sciences Branch, Islamic Azad University, Tehran, Iran Hamid Zaferani Arani Hamid_zaferani73@yahoo.com 100319475328460016865 100319475328460016865 Yes Young Researchers and Elite Club, Tehran Medical Sciences Branch, Islamic Azad University, Tehran, Iran