Secondary obsessive-compulsive syndromes: a systematic literature review resulting in 228 suspected cases

Secondary forms of obsessive-compulsive disorder (OCD) have clear underlying organic causes and are recognized as distinct nosological entities in the latest international classification systems. This study aims to provide a systematic overview of published cases of suspected secondary obsessive-compulsive syndromes. A systematic literature search of PubMed, Embase, Web of Science, and PsycINFO was conducted oriented on PRISMA criteria. Cases from case studies/series of patients with suspected secondary obsessive-compulsive syndromes and/or secondary obsessive-compulsive symptoms were included. Cases of obsessive-compulsive symptoms due to pediatric acute-onset neuropsychiatric syndrome (PANS) and pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS) were excluded. Overall, 228 cases of suspected secondary obsessive-compulsive syndromes were identified from 189 publications. Causal factors included brain lesions (25.4%), genetic syndromes (24.1%), head trauma (12.3%), autoimmune-inflammatory processes (11.8%), tumors (8.3%), neurodegeneration (7.5%), seizures (4.8%), pathogens (3.9%), metabolic processes (1.3%), or other reasons (0.4%). The age of the affected patients varied considerably (mean 37.3 ± 21.2 years, range 4-94 years, n = 226). Diagnostic abnormalities were identified through brain imaging (magnetic resonance imaging/computer tomography) in 66.2% of the sample and via blood analysis in 23.9%. In cases reporting the regions of the brain involvement, frontal lobe (34.3%) and the basal ganglia (26.5%) were mostly affected. The findings highlight a variety of suspected causes of secondary obsessive-compulsive syndromes, most frequently brain lesions, genetic syndromes, head trauma, and autoimmune-inflammatory processes. Identifying secondary obsessive-compulsive symptoms informed personalized therapies in a subgroup of published cases.