Biomarkers in young individuals with 22q11.2 deletion syndrome, a population at high risk for dopaminergic neuropsychiatric disease

Purpose Individuals with 22q11.2 deletion syndrome (22q11.2DS) show a wide range of somatic features. The syndrome also leads to increased risk of neuropsychiatric disorders including schizophrenia, attention deficit hyperactivity disorder and early-onset Parkinson’s disease, presumably mediated by alterations in dopaminergic neurotransmission. Potential biomarkers of these conditions are an increased size of the echogenic area of the substantia nigra (SN+) and reduced olfactory function. The aim of the study was to test potential biomarkers for the mentioned neuropsychiatric disorders in patients with 22q11.2DS. Methods Olfactory function (sensitivity and discrimination) was assessed with the Sniffin’ Sticks test. The maximal size of the echogenic area of the SN (SNmax in mm²) was evaluated by two blind raters. Findings of patients with 22q11.2DS and controls were compared in analyses of covariance. Results The sample for assessment of olfactory function comprised N = 60 patients (n = 37 males, m = 17.3 ± 8.8 years) and N = 60 controls. The sample for assessment of SN echogenicity comprised N = 50 patients (n = 30 males, m = 16.02 ± 7.8 years) and N = 50 controls. The group with 22q11.2DS showed impaired olfactory sensitivity (F _1,105 = 36.109, p  < .001, partial eta² = .256) and discrimination (F _1,109 = 51.248, p  < .001, partial eta² = .320) compared to controls. No significant group differences could be observed with regard to the SNmax ( p  = 0.167). Conclusions In this young sample previous findings were replicated demonstrating reduced olfactory function in 22q11.2DS, whereas no significant changes in SN were detected.