Quercetin, an over-the-counter supplement, causes neuroblastoma-like elevation of plasma homovanillic acid.

A 22-month-old boy, who regularly consumed the oral dietary supplement, quercetin, was suspected erroneously of having a catecholamine-producing tumor, based on elevated serum and urine levels of the dopamine metabolite, homovanillic acid (HVA). Subsequent studies of healthy adult volunteers showed that significant elevations in plasma HVA are a consequence of quercetin ingestion.