Question: What is (are) Periodic fever, aphthous stomatitis, pharyngitis and adenitis ?
Answer: Periodic fever, aphthous stomatitis, pharyngitis, cervical adenitis (PFAPA) is a periodic disease, which is a heterogeneous group of disorders characterized by short episodes of illness that regularly recur for several years alternated with healthy periods. PFAPA is characterized by high fevers lasting three to six days and recurring every 21 to 28 days, accompanied by some or all of the signs noted in its name, namely mouth sores (aphthous stomatitis), sore throat (pharyngitis), and enlarged lymph nodes (cervical adenitis). The syndrome usually occurs in children younger than five years; although it has been reported in children up to 13 years. The syndrome is sporadic and non-hereditary. The course of PFAPA can be persistent for years before spontaneous, full resolution.
Source: GARD

Question: What causes Periodic fever, aphthous stomatitis, pharyngitis and adenitis ?
Answer: What causes periodic fever, aphthous stomatitis, pharyngitis, cervical adenitis (PFAPA)? The cause of PFAPA is unknown, although viral or autoimmune causes have been suggested.
Source: GARD