What are AiArthritis Diseases?

Autoimmune & Autoinflammatory Arthritis Diseases

“AiArthritis” is a term for inflammation-driven arthritis caused by certain autoimmune and autoinflammatory diseases. In these conditions, the immune system misfires, mistakes healthy tissue for a threat, and triggers ongoing inflammation. This makes AiArthritis very different from common wear-and-tear arthritis (like osteoarthritis), which develops from joint use over time rather than immune dysfunction.

There are more than 100 recognized autoimmune and autoinflammatory (“Ai”) diseases, but only a few dozen commonly cause inflammatory arthritis. Because these conditions affect the immune system as a whole, inflammation can appear throughout the body — not just in the joints — impacting tissues, organs, and overall health.

Focusing specifically on the autoimmune diseases that include arthritis early in their course helps improve research, awareness, and patient care.

About 1 in 10 people worldwide live with at least one AiArthritis disease — including many “mystery patients” who have symptoms but no clear diagnosis yet. That’s roughly 450 million people. The odds are high that you or someone you know is dealing with these conditions or searching for answers. 

Autoimmune vs. Autoinflammatory — What’s the Difference?

There are two parts of the immune system that play a big role in autoimmune and autoinflammatory diseases: the “adaptive”  and the “innate” parts. As research into the immune system has advanced, some diseases once thought to be autoimmune (which stem from the adaptive part) are now categorized as autoinflammatory (which stem from the innate part). Some even fall somewhere in between the two, because at times these systems can cross communicate with each other.

Both types involve the immune system, but they behave differently.

These conditions stem from the adaptive immune system, the part that learns and responds to things like infections, hormones, and environmental triggers. If someone is genetically susceptible, these triggers can cause the immune system to attack the body’s own tissues.

Autoimmune Arthritis Diseases: Rheumatoid arthritis, psoriatic arthritis, lupus, axial spondyloarthritis, Sjogren’s disease, Undifferentiated Disease, Crohn’s Disease, Juvenile Idiopathic Arthritis (most subtypes except systemic JIA), Relapsing Polychondritis (RP), Mixed Connective Tissue Disease (MCTD), Antisynthetase Syndrome (ASS), Systemic Sclerosis (Scleroderma), Palindromic Rheumatism (PR)

These come from the innate immune system, the body’s built-in first line of defense. Many are tied to genetic mutations that cause sudden or ongoing inflammatory episodes even when nothing specific has triggered them.

Autoinflammatory Arthritis Diseases: Adult-onset Still’s disease,  Behcet’s Disease, systemic juvenile arthritis.CAPS (Cryopyrin-Associated Periodic Syndromes), VEXAS Syndrome, Schnitzler Syndrome, CNO/CRMO (Chronic Nonbacterial Osteomyelitis/Chronic Recurrent Multifocal Osteomyelitis), FMF (Familial Mediterranean Fever), HIDS (Hyper-IgD Syndrome / Mevalonate Kinase Deficiency)

*Regardless if the disease is autoimmune or autoinflammatory, symptoms and disease activity varies per person.

**Undifferentiated diagnoses occur when a person exhibits disease traits of one or more AiArthritis diseases, but no one disease has fully developed enough to meeting diagnostic criteria for any one disease. Our conclusion is based on research conducted in 2013, the Early Symptoms of AiArthritis study, which based our 50% theory on existing research.