**Core Concept**
Systemic juvenile idiopathic arthritis (sJIA) is a subtype of juvenile idiopathic arthritis (JIA) characterized by the presence of systemic symptoms, including fever, rash, lymphadenopathy, and serositis. The pathogenesis of sJIA involves an abnormal immune response, with an overproduction of pro-inflammatory cytokines, particularly interleukin-1 beta (IL-1β).

**Why the Correct Answer is Right**
The characteristic fever in sJIA is diurnal, meaning it typically follows a daily pattern of spiking in the late afternoon or evening, often accompanied by an elevated white blood cell count. This diurnal fever pattern is thought to be related to the circadian rhythm of the hypothalamic-pituitary-adrenal axis, which regulates the body's response to inflammation. The fever in sJIA is also often accompanied by other systemic symptoms, such as rash, lymphadenopathy, and serositis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the fever in sJIA is not typically continuous or persistent, but rather follows a diurnal pattern.
**Option B:** This option is incorrect because the fever in sJIA is not typically associated with an elevated body temperature above 104°F (40°C), but rather a more moderate elevation.
**Option C:** This option is incorrect because the fever in sJIA is not typically caused by an infection, but rather by an abnormal immune response.

**Clinical Pearl / High-Yield Fact**
The diurnal fever pattern in sJIA is a classic clinical finding that can help differentiate it from other forms of JIA. Remember that the presence of systemic symptoms, including fever, rash, lymphadenopathy, and serositis, is a key characteristic of sJIA.

**Correct Answer: C. Non-infectious fever**