Still’s disease is a rare disorder associated with episodes of salmon-colored skin rashes and spiking fever accompanied by joint pain.
Still’s disease was named after an English pediatric physician, George F. Still. It is classified into two major types based on the onset time: (1) Adult onset Still’s disease (AOSD) (also known as “Wissler-Fanconi syndrome”) and (2) systemic onset juvenile idiopathic arthritis (SOJIA).
The overall incidence of Still’s disease is less than 1 out of 100,000 individuals. Onset of Still’s disease is rare in individuals between the age of 25 to 35 years. AOSD occurs mainly in individuals between the age of 15 to 25 years, and 35 to 45 years. However, in some individuals, it may be triggered during old age (greater than 50 years). The more common type of Still’s disease is SOJIA, with onset time during infancy or childhood. SOJIA comprises 10-20% of total juvenile rheumatoid arthritis cases. Men and women are believed to be equally affected by Still’s disease, however, some reports indicate that it is more common in women.
The signs and symptoms of AOSD and SOJIA vary significantly amongst the patients. Other than the classical signs including rashes, fever, and arthritic pain, Still’s disease may also cause inflammatory effects on internal organs. Swelling of lymph nodes, tissues, and organs (mainly joints), and fatigue are also reported in several cases. In some patients, the episodes recur within a few weeks or months, while in others, they may not reappear for several years. Due to a substantial difference in the intensity and recurrence frequency of symptoms amongst the patients, an accurate diagnosis often becomes tricky.
Causes and Risk Factors of Still’s Disease
There are no specific established risk factors for Still’s disease. People among the aforementioned age ranges are predisposed to the development of Still’s disease. Some evidence suggests that women are at slightly higher risk of developing it compared to men.
Still’s disease is idiopathic in nature, meaning the exact cause of Still’s disease is unknown. Researchers propose multiple theories explaining the etiology of Still’s disease, these include:
- Bacterial or viral infection: This is considered as a major potential trigger for development of Still’s disease. A healthy human body creates antibodies to protect itself against such foreign invasions by microbes or any other external antigens. However, in certain individuals, this antibody response mechanism seems to behave erratically (e.g. an exaggerated/abnormal antibody response to a toxic antigen). This, in turn, causes a defected chain of events manifesting into the symptoms of Still’s disease.
- Autoimmune or hypersensitivity disorder: Where the immune system erroneously attacks host cells.
- Auto-inflammatory disorder: Auto-inflammatory disorders (different from autoimmune disorders) are characterized by recurrent episodes of inflammation due to inherent abnormality in the immune system.
- Cytokine disorder: Cytokines (chemicals secreted from immune system cells) which play a vital role in normal immunological function are also on researchers’ radar. Interleukin-1 (IL-1) is a type of cytokine which mediates cell response to inflammation. Abnormal IL-1 levels have been found in several patients with Still’s disease. Other cytokines such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) may also play a vital role in immune mediated response associated with Still’s disease. The detailed mechanisms and pathways of these chemical mediators, and possible spots therein for therapeutic intervention are being investigated in preclinical and clinical trials.