Still’s disease is a rare systemic inflammatory condition that causes joint inflammation, fevers, and rashes. It is an auto-inflammatory disorder, meaning the body’s innate immune system attacks its own tissues, leading to widespread inflammation. The exact cause of Still’s disease remains unknown, and its presentation varies significantly, making it a complex disorder to identify and manage.
The Two Forms of Still’s Disease
The term “Still’s disease” describes the same underlying condition, distinguished by the age at which symptoms first appear. When the disorder begins in individuals younger than 16, it is called Systemic-onset Juvenile Idiopathic Arthritis (SoJIA). When symptoms manifest at age 16 or older, it is termed Adult-Onset Still’s Disease (AOSD), with most diagnoses occurring between the ages of 16 and 35. Despite the different names, SoJIA and AOSD are clinically regarded as the same disease, sharing core symptoms and inflammatory pathways.
Characteristic Symptoms
The presentation of Still’s disease is recognized by a trio of symptoms. A primary symptom is high, spiking fevers that occur daily, often reaching 102°F (39°C) or higher. These fevers peak in the late afternoon or evening and return to normal levels between episodes. This pattern can persist for a week or longer.
Accompanying the fever is a distinctive, non-itchy rash. The rash is often described as salmon-pink and appears on the trunk, arms, and legs. A notable feature of this rash is its transient nature; it tends to emerge with the fever spikes and fade as body temperature subsides.
The third component is arthritis, involving joint pain, swelling, and stiffness. The knees and wrists are among the most frequently affected joints, though inflammation can occur in others. Beyond these indicators, individuals may experience a severe sore throat, which can be an early sign. Other common symptoms include swollen lymph nodes, especially in the neck, and muscle pain that coincides with the fevers.
The Diagnostic Process
There is no single test for Still’s disease. Its diagnosis is one of exclusion, requiring physicians to rule out other conditions with similar symptoms, such as infections, lymphoma, and other rheumatic diseases.
To support a diagnosis, doctors use a combination of clinical findings and laboratory tests. Blood tests reveal specific inflammatory markers, including an elevated white blood cell count (leukocytosis), high erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). A high level of serum ferritin, a protein that stores iron, is also a telling laboratory finding, though it can be present in other conditions.
Physicians use established diagnostic criteria, such as the Yamaguchi criteria, to help structure the diagnosis. Major criteria include the characteristic high fever, joint pain lasting at least two weeks, the typical rash, and an elevated white blood cell count. Minor criteria include a sore throat, swollen lymph nodes or spleen, and abnormal liver function tests. A diagnosis is considered when a specific number of these criteria are met after other diseases have been excluded.
Treatment Approaches
Treatment for Still’s disease focuses on controlling inflammation and is tailored to the condition’s severity. For milder symptoms, the first line of therapy involves nonsteroidal anti-inflammatory drugs (NSAIDs) to help reduce joint pain and control fever.
For more significant inflammation, corticosteroids like prednisone are frequently used. These anti-inflammatory drugs are effective at managing severe systemic symptoms like high fevers and organ inflammation. Due to potential side effects with long-term use, the goal is to use them for the shortest duration possible at the lowest effective dose.
If symptoms persist or corticosteroids cannot be tapered, physicians may introduce disease-modifying antirheumatic drugs (DMARDs) like methotrexate. For patients who do not respond adequately to these therapies, biologic drugs offer a more targeted approach. These medications block specific inflammatory proteins, with inhibitors of interleukin-1 (IL-1) and interleukin-6 (IL-6) being particularly effective.
Disease Progression and Complications
The long-term course of Still’s disease is variable and can follow one of three patterns. Some individuals experience a monophasic pattern: a single episode of the disease that resolves and does not return. Others may have an intermittent course, characterized by recurrent flares of symptoms with periods of remission. A third group develops a chronic form of the disease, where arthritis becomes the dominant feature, potentially leading to joint damage.
A serious, though rare, complication of Still’s disease is Macrophage Activation Syndrome (MAS). This life-threatening condition is caused by a severe, uncontrolled overreaction of the immune system. In MAS, immune cells called macrophages become excessively activated, leading to a massive inflammatory response that can cause high, continuous fevers, a sharp drop in blood cell counts, and severe organ dysfunction. MAS is a medical emergency that requires immediate treatment to suppress the inflammation.