Presence of antibrain antibodies in obsessive-compulsive disorder secondary to pineal gland germinoma: a case report.

Obsessive-compulsive disorder (OCD) is a neuropsychiatric illness characterized by the experience of recurrent, intrusive, and distressing thoughts, images, and urges to action. It was considered a rare disorder, but new data have revealed that it is, in fact, a relatively common illness, particularly in childhood and adolescence. The etiology and pathophysiology of OCD are not well understood. Various factors involving psychosocial, genetic, neuroanatomic, and neurochemical factors have been identified. A subset of patients with pediatric-onset OCD and tic syndrome (e.g., Tourette syndrome) have a symptom onset or exacerbation associated with group A β-hemolytic streptococcal infection. The term “pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections” (PANDAS) has been coined to describe those patients with evidence of recent group A β-hemolytic streptococcal infection. Numerous studies have reported the presence of antibrain, antineuron, and anti–basal ganglia antibodies in these patients. Pavone et al. reported a study showing 64% of patients with PANDAS are positive for anti–basal ganglia antibodies, but only 9% were positive compared with the group with group A β-hemolytic streptococcal infection without PANDAS. Snider and Swedo proposed an autoimmunemodel where antibodies against group A β-hemolytic streptococcus have cross-reactions with specific brain antigens and result in movement disorder andOCD symptoms. The target antigens remain unknown; however, a number of studies have reported identification of some neuronal proteins at 40, 60, and 83 kDa as common target proteins. Limbic encephalitis is an inflammation of the limbic system, which includes the thalamus, hypothalamus, hippocampus, and amygdala. It has been reported as paraneoplastic syndrome associated with several malignancies (e.g., lung, ovary, breast). Antibodies targeting the oncoproteins have crossreactions with cellular components in brain resulting in neurologic symptoms. A series of antigens have been identified, such as Hu,Ma, Ri, and voltage-gated potassium channel. More recently, anti–N-methylD-aspartate (NMDA) receptor encephalitis has been characterized. It has predominant psychiatric symptoms, such as delusions and hallucinations, during the early phase of the illness and often leads patients to seek psychiatric evaluation and treatment. The presence of autoantibodies against NMDA receptor, particularly NR1 subunit, in both serum and cerebral spinal fluid of patients has led to the hypothesis of an autoimmune-mediated NMDA dysfunction where autoantibodies alter the structure and function of the receptor. Effective treatment with immune modulators further supports the hypothesis of autoimmune mechanism of the disease.