Obsessive-compulsive disorder (OCD) is a serious and common psychiatric disorder with a prevalence of approximately 1-3% in adults. The onset of OCD has a bimodal age distribution, usually manifesting first in late childhood and early adolescence and later appearing in early adulthood. OCD is a multifactorial disorder with an interplay of biological, psychological, and external factors, and immune system activation is also an important etiology.

OCD induced by pathogenic infections

Obsessive-compulsive symptoms (OCS) may be associated with Pediatric Autoimmune Neuropsychiatric Disorder (https://autoimmune-disease.creative-biolabs.com/neurological-system.htm)Associated with Streptococcal infection (PANDAS) in children with group A streptococcal infection. A Danish study including 1,067,743 children found that children who tested positive for streptococci had an increased risk of developing OCD, and that first-degree relatives of those with OCD were similarly more susceptible to streptococcal infection.

PANDAS has been expanded to involve other diseases (Mycoplasma pneumoniae, Burkholderia spongiformis, Borna disease virus, and toxoplasmosis gondii) in recent years, and the name pediatric acute onset childhood neuropsychiatric syndrome (PANS) has been coined.

PANDAS autoantibody
The positive rates of three autoantibodies, α-dopamine receptor D1 (a-D1R), calcium/calmodulin-dependent protein kinase CaMKII, and anti-streptavidin O, in the serum of PANDAS patients were 71.4%, 71.4%, and 60.0%, respectively.

Neurological autoimmune diseases
Secondary OCD can also occur in autoimmune encephalitis and is associated with central nervous system autoimmune diseases such as multiple sclerosis.

Systemic autoimmune disorders can also cause OCD syndrome. Patients with past autoimmune disease had a greater prevalence of OCD, especially those with systemic lupus erythematosus, dermatomyositis, and dry syndrome, according to a national study from Taiwan that looked at 63,165 patients with a history of autoimmune disease and 315,825 controls. Another Swedish national study of 30,082 OCD patients found that they were strongly linked to several autoimmune diseases: individuals with OCD had a 43% greater risk of getting any autoimmune disease.

Autoimmune OCD therapy
Based on the possible mechanisms of autoimmune OCD pathogenesis, there are three types of treatment strategies.
1. Conventional psychiatric drugs
2. Anti-infective therapy
3. Anti-inflammatory therapy
4. Immunotherapy

At the moment, the therapy of antibody-associated autoimmune neurologic diseases is based on professional recommendations and information from case reports and case series. The goal of immunotherapy is to achieve the best possible results by reducing nervous system inflammation and symptoms, preventing relapses, and minimizing adverse effects. Antibody titers have several limitations in patient management, and they rarely help guide therapy, which should be based on clinical findings because titers are not reliable markers of disease severity, but they can occasionally predict relapses and support the use of long-term immunotherapy for prevention.

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