Case Report: Successful Remission With Upadacitinib in Behcet's Syndrome Following a History of PFAPA Syndrome.

Recent studies have revealed a shared genetic background and pathogenesis between Behcet's syndrome (BS) and periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) syndrome. This study suggests genetic similarities between recurrent aphthous stomatitis, PFAPA syndrome, and BS and proposes the concept of Behcet's spectrum disorders. An 18-year-old female with a history of PFAPA syndrome who had experienced repeated attacks until puberty visited our hospital complaining of oral ulcers, arthralgia, rash, and abdominal pain that had persisted for 2 weeks. Colonoscopy revealed a deep ulcer in the ileocecal region. Pathological findings showed no evidence suggestive of viral infection, malignancy, or vasculitis, and only nonspecific inflammatory cell infiltration. After ruling out various autoinflammatory diseases through genetic testing, the patient was diagnosed with Behcet's spectrum disorder. The patient was refractory to adalimumab and achieved remission after upadacitinib therapy. Genetic similarities have been reported between PFAPA syndrome and BS, involving genes such as IL-10 and IL-12A. Since the IL-10, IL-12, and IL-23 pathways can be blocked by JAK inhibitors, JAK inhibition therapy may be a potentially effective treatment option for Behcet's syndrome in a patient with a history of PFAPA syndrome.