High diagnostic value of plasma Niemann-Pick type C biomarkers in adults with selected neurological and/or psychiatric disorders.

Late-onset Niemann-Pick type C (NP-C) is a rare, underdiagnosed lysosomal disease with neurological manifestations. A specific treatment, miglustat, can stabilize the disease if given early. Recently, three plasma screening biomarkers (PSBs) were developed [cholestane3β,5α,6βtriol (C-triol), 7-ketocholesterol (7-KC), and lysosphingomyelin-509 (LSM-509)], allowing a simpler and quite robust screening of patients suitable for genetic testing. The objective of our study was to evaluate practical utility and feasibility of large-scale PSB screening for NP-C in selected adult patients. Patients were prospectively enrolled if they showed, starting from 12 years of age, at least one of the three initial neuro-psychiatric manifestations described in NP-C: (1) gait disorder (cerebellar and/or dystonic); (2) cognitive decline with frontal lobe syndrome; (3) atypical psychosis. PSBs were measured in plasma of all patients and, if positive (LSM-509 and/or C-triol + 7-KC elevated), sequencing of NPC1 and NPC2 genes was performed. A total of 251 patients [136 males, 115 females; median age 42.1 (range 12.2-85.6) years] were screened. Six patients had positive PSBs. Two were confirmed to have NP-C (0.8% diagnostic yield, both with all three PSBs highly increased, especially LSM-509). False-positive rate was 1.2%, which was identical if only considering LSM-509. By contrast, false-positive rates were 8.1% and 5.7% for 7-KC and C-triol, respectively. We showed that selecting patients with neurologic and/or psychiatric symptoms consistent with NP-C for large-scale PSB screening is a simple and valid strategy to identify new adult NP-C patients, and would probably lead to earlier diagnosis and treatment administration if widely applied.