Still’s Disease, known in adults as Adult-Onset Still’s Disease (AOSD), is a rare systemic inflammatory condition. It is classified as an autoinflammatory disorder involving widespread inflammation caused by an overactivation of the innate immune system. While the exact cause remains unknown, the pattern of early symptoms is a fundamental guide for diagnosis, distinguishing it from more common illnesses.
The Hallmark Symptom: Distinctive Fever Patterns
The most common and defining early sign of Still’s Disease is a specific type of high fever that occurs daily, referred to as quotidian. This fever typically spikes to 102°F (39°C) or higher, often occurring once a day in the late afternoon or evening. A key characteristic is the rapid return to a normal or near-normal temperature between spikes, a fluctuation that can be as wide as 7.2°F (4°C) within a few hours. This intermittent, spiking fever is often accompanied by profound sweating and sometimes shaking chills during the temperature ascent. The persistence of this specific fever pattern for at least a week is an important diagnostic criterion.
Cutaneous and Musculoskeletal Manifestations
Early indicators of Still’s Disease involve the skin and musculoskeletal system. A characteristic skin manifestation is the evanescent, non-itchy, salmon-colored rash, which appears in a majority of patients. This rash is macular (flat) or maculopapular (slightly raised) and typically appears on the trunk, neck, and proximal extremities. The rash is transient, often appearing only briefly, typically coinciding with the daily fever spike and fading rapidly as the temperature drops. In some individuals, heat or rubbing of the skin can induce the rash.
Joint and muscle involvement is also a prominent early symptom, manifesting initially as severe arthralgia (joint pain) and myalgia (muscle aches). This joint pain is often debilitating and present in a large percentage of patients at the onset of the disease. The pain may affect multiple joints, most commonly the knees, wrists, and ankles. While true arthritis, involving joint swelling and potential damage, may develop later, the initial, intense joint and muscle aches are a hallmark of the early systemic phase.
Systemic Indicators and Associated Features
Other systemic symptoms often accompany the onset of Still’s Disease. A persistent and severe sore throat is reported in more than half of patients and can precede the fever and other symptoms by several days or weeks. This pharyngitis is typically inflammatory, but microbiological tests for common infections are negative. Lymphadenopathy, or the swelling of lymph nodes, is another common finding, particularly in the neck. This enlargement is usually diffuse and symmetrical. Enlargement of the liver (hepatomegaly) and spleen (splenomegaly) can also occur early, indicating a widespread inflammatory impact on internal organs. Other associated features can include:
- General malaise
- Profound fatigue
- Elevated liver enzymes
- Inflammation of the membranes lining the heart or lungs (serositis)
Differentiating Still’s Disease from Common Illnesses
The early signs of Still’s Disease frequently mimic common viral infections, such as influenza or mononucleosis, which complicates the initial diagnosis. A central differentiating factor is the persistence and severity of the symptoms, particularly the recurring high fever, which is resistant to typical antibiotic treatment. Diagnosis relies heavily on ruling out other conditions that can cause similar symptoms, including infections, certain cancers like lymphoma, and other autoimmune diseases. Blood tests play a supporting role by revealing signs of severe inflammation that are uncommon in simple viral illnesses. Specifically, blood tests show a marked elevation in inflammatory markers, such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), and a dramatic increase in serum ferritin, an iron storage protein, often exceeding 1,000 ng/ml, is highly suggestive of the condition.