What is reactive arthritis? Reactive arthritis happens when an infection causes joint pain and swelling. A bacterial infection in the digestive or urinary tract or the genitals usually triggers the condition, but arthritis symptoms typically do not start until a few weeks after you have recovered from the infection. The most common features of reactive arthritis are inflammation of the joints (especially the knees and ankles), eyes, and urinary tract, but not everyone gets all three, or they might not happen at the same time.

What is osteogenesis imperfecta? Osteogenesis imperfecta (OI) is a disease that causes your bones to break (fracture) easily. OI is also called brittle bone disease. Your symptoms may be mild or severe, depending on the type of OI you have.

What is pemphigus? Pemphigus is a rare disease that causes blistering on many parts of the body, including the skin and the inside of the mouth, nose, throat, eyes, and genitals. In pemphigus, the immune system mistakenly attacks cells in the top layer of the skin.

What is alopecia areata? Alopecia areata is a disease that causes hair loss. In alopecia areata, the immune system attacks the structures in skin that form hair (hair follicles). Alopecia areata usually affects the head and face, though hair can be lost from any part of the body. Hair typically falls out in small, round patches about the size of a quarter. In some cases, hair loss is more extensive.

What is gout? Gout is a type of arthritis that causes pain and swelling in your joints, usually as flares that last for a week or two, and then go away. Gout flares often begin in your big toe or a lower limb. Gout happens when high levels of a substance called serum urate build up in your body. When this happens, needle-shaped crystals form in and around the joint. This leads to inflammation and arthritis of the joint. However, many people with high levels of serum urate will not develop gout. With early diagnosis, treatment, and lifestyle changes, gout