Surreal illustration of a spine intertwined with a salmon-colored rash, symbolizing ankylosing spondylitis and adult-onset Still's disease.

Uncommon Connections: When Arthritis and Rare Diseases Intertwine

Jordan Keane in Health & Wellness August 2025 • 4 min read.

"Exploring the rare overlap between ankylosing spondylitis and adult-onset Still's disease and what it means for diagnosis and treatment."

Ankylosing spondylitis is a chronic inflammatory condition primarily affecting the spine, leading to pain and stiffness. It's a type of arthritis that, while impactful, doesn't usually present with systemic symptoms like high fever or significant weight loss. When these symptoms appear, it prompts doctors to consider other underlying conditions or associated diseases.

Adult-onset Still's disease (AOSD) is a rare systemic inflammatory disorder. It’s characterized by high spiking fevers, a distinctive salmon-colored rash, joint pain, and various systemic manifestations. Diagnosing AOSD can be challenging, as it often requires ruling out other conditions.

While it's uncommon, ankylosing spondylitis and adult-onset Still's disease can occur together. This raises questions about a possible link between the two conditions. Let's explore a case that highlights this rare association and what it might mean for understanding and treating these complex diseases.

Decoding the Overlap: Ankylosing Spondylitis and Adult-Onset Still's Disease

Surreal illustration of a spine intertwined with a salmon-colored rash, symbolizing ankylosing spondylitis and adult-onset Still's disease.

In a recent medical case, a 31-year-old man with a decade-long history of ankylosing spondylitis developed symptoms that pointed towards adult-onset Still's disease. He initially presented with typical ankylosing spondylitis symptoms, including inflammation of the spine and asymmetrical joint pain. However, he began experiencing high fevers, fatigue, and overall decline in health.

Further examination revealed a range of symptoms that aligned with AOSD, making the diagnosis more complex. These symptoms included:

High fever spikes, reaching 40°C (104°F).
Severe fatigue and muscle weakness, making walking difficult.
Swollen lymph nodes in the neck and groin.
Elevated inflammatory markers, such as C-reactive protein (CRP) at 300 mg/L and an elevated erythrocyte sedimentation rate (ESR) at 80 mm/hr.
High white blood cell count (15,000 elements/mm³) with a majority of neutrophils (88%).
Anemia (hemoglobin at 8.5 g/dl).
Inflammatory joint fluid, sterile and without crystals.
Appearance of a salmon-colored, maculopapular rash during fever spikes.

Standard treatments, including antibiotics, proved ineffective. After further testing ruled out other conditions, doctors suspected AOSD. A key finding was a very high ferritin level (4787) with a low glycosylated fraction (15%). The patient was then started on high-dose prednisolone (60 mg/day), a type of corticosteroid. This treatment led to rapid improvement: the fever disappeared, joint inflammation decreased, lymph nodes normalized, and inflammatory markers improved.

Unraveling the Mystery: What Does This Association Mean?

The co-occurrence of ankylosing spondylitis and adult-onset Still's disease is rare but significant. When a patient with known ankylosing spondylitis presents with prolonged fever, swollen lymph nodes, and elevated inflammatory markers, doctors should consider the possibility of AOSD. More research is needed to fully understand the relationship between these conditions. Further studies may reveal common pathways or triggers that could lead to more targeted and effective treatments for both diseases.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.11604/pamj.2017.28.132.5607, Alternate LINK

Title: Spondylarthrite Ankylosante Et Maladie De Still: Un Lien Physiopathologique Ou Une Simple Association?

Subject: General Medicine

Journal: Pan African Medical Journal

Publisher: Pan African Medical Journal

Authors: Nassira Aradoini, Sofia Talbi, Hamida Azzouzi, Fatima Zahra Abourazzak, Hajar Khibri, Rhizlane Berrady, Wafaa Bono, Taoufik Harzy

Published: 2017-01-01

Everything You Need To Know

What are the primary characteristics of ankylosing spondylitis?

Ankylosing spondylitis is a chronic inflammatory condition mainly affecting the spine. Its main symptoms include pain and stiffness. Unlike adult-onset Still's disease, ankylosing spondylitis typically does not present with systemic symptoms like high fevers or significant weight loss. This difference is crucial for differentiating the two conditions during diagnosis.

What are the key indicators that might suggest someone with ankylosing spondylitis could also have adult-onset Still's disease?

If a patient already diagnosed with ankylosing spondylitis begins to experience prolonged fevers, swollen lymph nodes, and a significant increase in inflammatory markers, such as a high C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR), doctors should consider the possibility of adult-onset Still's disease. The appearance of a salmon-colored rash during fever spikes is also a key indicator.

Why is diagnosing adult-onset Still's disease challenging, and what specific factors complicate the diagnosis?

Diagnosing adult-onset Still's disease can be challenging because it often requires ruling out other conditions. The presence of symptoms like high spiking fevers, a salmon-colored rash, joint pain, and various systemic manifestations can mimic other illnesses. In the case mentioned, the patient’s presentation with symptoms like high fevers, fatigue, muscle weakness, swollen lymph nodes, and elevated inflammatory markers alongside a history of ankylosing spondylitis made the diagnosis complex. A key finding, such as a very high ferritin level with a low glycosylated fraction, can provide clues toward diagnosis.

How does treatment for adult-onset Still's disease differ from that for ankylosing spondylitis, and what was the treatment approach in the case discussed?

Treatment for adult-onset Still's disease often involves systemic therapies to address the widespread inflammation, while ankylosing spondylitis treatments primarily focus on managing spinal inflammation and pain. In the case provided, standard treatments, including antibiotics, proved ineffective. The patient was treated with high-dose prednisolone, a corticosteroid, which led to a rapid improvement. The fever disappeared, joint inflammation decreased, lymph nodes normalized, and inflammatory markers improved. This highlights the systemic nature of adult-onset Still's disease and the need for therapies that address the body-wide inflammation.

What is the significance of the co-occurrence of ankylosing spondylitis and adult-onset Still's disease, and what further research is needed?

The co-occurrence of ankylosing spondylitis and adult-onset Still's disease, though rare, is significant because it raises questions about a potential link between the two conditions. It suggests that there might be common pathways or triggers that could lead to the development of these autoimmune diseases. Further research is needed to fully understand this relationship, potentially leading to more targeted and effective treatments for both conditions. Studying these overlaps could unveil new insights into the underlying mechanisms of autoimmune diseases.