PANDAS, is an abbreviation for Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections. The term is used to describe a subset of children who have Obsessive Compulsive Disorder (OCD) and/or tic disorders such as Tourette's Syndrome, and in whom symptoms worsen following strep. infections such as "Strep throat" and Scarlet Fever.
The children usually have dramatic, "overnight" onset of symptoms, including motor or vocal tics, obsessions, and/or compulsions. In addition to these symptoms, children may also become moody, irritable or show concerns about separating from parents or loved ones. This abrupt onset is generally preceeded by a Strep. throat infection.
What is the mechanism behind this phenomenon? At present, it is unknown but researchers at the NIMH are pursuing a theory that the mechanism is similar to that of Rheumatic Fever, an autoimmune disorder triggered by strep. throat infections. In every bacterial infection, the body produces antibodies against the invading bacteria, and the antibodies help eliminate the bacteria from the body. However in Rheumatic Fever, the antibodies mistakenly recognize and "attack" the heart valves, joints, and/or certain parts of the brain. This phenomenon is called "molecular mimicry", which means that proteins on the cell wall of the strep. bacteria are similar in some way to the proteins of the heart valve, joints, or brain. Because the antibodies set off an immune reaction which damages those tissues, the child with Rheumatic Fever can get heart disease (especially mitral valve regurgitation), arthritis, and/or abnormal movements known as Sydenham’s Chorea or St. Vitus Dance.
In PANDAS, it is believed that something very similar to Sydenham’s Chorea occurs. One part of the brain that is affected in PANDAS is the Basal Ganglia, which is believed to be responsible for movement and behavior. Thus, the antibodies interact with the brain to cause tics and/or OCD, instead of Sydenham Chorea.