Paraneoplastic syndrome-associated neuronal antibodies in adult ADHD

•No associations between ADHD and antibodies associated with PNS were found.•Some ADHD patient sera showed positive cytoplasmic staining of Purkinje cells (PCs).•The PC reactivity was probably due to the presence of uncharacterized antibodies.•Detection of antibodies with unclear significance should be interpreted with caution.

A high seroprevalence of Yo antibodies targeting cerebellar Purkinje cells was recently reported in children with attention deficit/hyperactivity disorder (ADHD). We investigated the presence of 8 paraneoplastic neurological syndrome (PNS)-associated antibodies including anti-Yo in 169 adult ADHD patients. No associations between ADHD and serum Yo antibodies or other antibodies associated with PNS were found. However, 10 out of 48 ADHD patient sera analyzed by immunofluorescence presented antibodies targeting cerebellar Purkinje cells. This reactivity probably represents the presence of low levels of antibodies against multiple cellular hitherto unknown antigens with little to no clinical significance.

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