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AS Symptoms – Mild Fever

Spondyloarthritis (SpA), including ankylosing spondylitis (AS), is a group of chronic arthritis conditions that cause inflammation in the joints. Each person with SpA can have a different set of symptoms, or presentation, of the disease. In addition to the joint symptoms, people with SpA can have extra-articular (beyond the joint) symptoms, including eye inflammation (uveitis), skin rash, and fever.1

Symptoms of AS often begin in late adolescence or early adulthood (before age 45), although some people experience the onset of symptoms later in life or in childhood. A mild fever may be an early symptom of AS. The most common symptom of early AS is low back pain and stiffness, which is worse in the morning (after a night’s sleep) or after periods of inactivity and improves with movement or a warm shower. Other early symptoms may include fatigue, pain in the neck, or heel pain.2

Getting a diagnosis of ankylosing spondylitis can be challenging

Diagnosing AS and other forms of SpA is not a simple or straightforward process. On average, it can take 8-11 years from when symptoms begin to when a person receives a diagnosis.3 One of the reasons diagnoses in the early stages can be so challenging is that early signs, like low back pain or fever, are common and can be caused by a variety of other conditions. If a person’s only symptom is a mild fever, doctors may not suspect SpA, as SpA is typically known for joint inflammation. It can be very challenging for a diagnosis of SpA to be made when patients only have non-joint (non-articular) symptoms.1

Why does AS cause a fever?

The inflammatory response is the immune system’s natural reaction when cells are stressed or damaged, or when there is a foreign invader (like a viral, fungal, or bacterial infection). Although inflammation in AS is viewed as having negative consequences, it is a necessary process in the body to recruit defense systems, remove damaged or diseased cells, and trigger repair mechanisms.4

The inflammatory response causes a cascade of chemicals to be released in the body. Some of these chemical processes can cause a fever, an increase in the body’s temperature. During a fever, the skin may appear pale and an individual may experience shivering. Despite the internal temperature of the body being raised during a fever, the individual may feel chilled. Fevers can also cause the body to sweat, which cools the skin as it evaporates. There are a number of conditions that can cause the body to have a fever, including infections, some types of blood cancer, and chronic conditions like Crohn’s disease, a type of inflammatory bowel disease.4

In some cases, the pattern of temperature changes in a fever can help doctors determine the cause of the fever. For example, a continuous fever over 100.4 degrees Fahrenheit can indicate a viral or bacterial infection. A fever that may occur with SpA is a mild fever and may be initially classified as a fever of unknown origin. Fevers of unknown origin generally last more than three weeks. These types of fevers may also be caused by cancers, certain infections, and autoimmune diseases.5

Managing fever

Generally, fevers are treated with non-steroidal anti-inflammatory drugs (NSAIDs), which are available over-the-counter. Common NSAIDs used for fever include aspirin and ibuprofen. NSAIDs can help relieve the symptoms of a fever and help bring the body temperature down.6

Written by: Emily Downward | Last reviewed: February 2019
  1. Byun SJ, Bae WH, Jung SM, Lee SW, Park YB, Song JJ. Fever as an initial manifestation of spondyloarthritis: A retrospective study. PLoS One. 2017;12(9):e0184323. Published 2017 Sep 14. doi:10.1371/journal.pone.0184323
  2. Most common symptoms. Spondylitis Association of America. Available at Accessed 1/31/19.
  3. Lipton S, Deodhar A. The new ASAS classification criteria for axial and peripheral spondyloarthritis. Int J Clin Rheumatol. 2012;7(6):675-682. Available at Accessed 1/31/19.
  4. Inflammation and fever. OpenStax Microbiology. Available at[email protected] Accessed 1/31/19.
  5. Fever and inflammation. Amboss. Available at Accessed 1/31/19.
  6. Fever: what you need to know. Medical News Today. Available at Accessed 1/31/19.