The primary characteristic of periodic fever syndrome is cyclical fever episodes. These fever attacks begin suddenly, range from 38.9°C to 41°C, and typically last between 3 to 6 days; they usually do not exceed 7 days and often resolve spontaneously. These attacks recur approximately every 28 days on average (though they can vary between 26-30 days), which translates to an average of 11-12 fever episodes per year. Between attacks, the child appears completely healthy and continues normal growth and development. Aphthous ulcers in the mouth may also be observed with the fever. Although there is no specific laboratory test, diagnosis is made through clinical evaluation and requires the observation of at least three typical fever episodes.