Older-onset levodopa-responsive parkinsonism with normal DAT-SPECT and pterin hypometabolism. Issue 5 (7th May 2021)

• Record Type: Journal Article
• Authors: Togo, Kazuyuki; Ishihara, Toshiya; Yamamoto, Kenji; Sawada, Hideyuki
• Is Part Of: BMJ case reports. Volume 14:Issue 5(2021)
• Publication Date: 2021-05-07
• Subjects: movement disorders (other than Parkinsons) -- drugs: CNS (not psychiatric) -- neuroimaging; Medicine -- Case studies -- Periodicals; 610.5
• DOI: 10.1136/bcr-2020-240067
• Languages: English
• ISSNs: 1757-790X

Abstract

Abstract : Pterin species participate in dopamine biosynthesis, and abnormal pteridine metabolism contributes to reduced dopamine. GTP cyclohydrolase 1 (GCH-1) deficiency, which triggers pteridine hypometabolism and normally develops in childhood, can mediate an adult-onset decrease in levodopa production and dopa-responsive dystonia (DRD), with normal dopamine transporter single-photon emission computed tomography (DAT-SPECT). A recent study described normal DAT-SPECT in adult-onset cases with GCH-1 mutations, clinically diagnosed with Parkinson's disease, which raises the possibility that the abnormal metabolism of pteridine may be a differential diagnosis for adult-onset parkinsonism. We report an older patient with levodopa-responsive parkinsonism with normal DAT-SPECT, or scans without evidence of dopamine deficit (SWEDD), whose biochemical analysis showed pterin hypometabolism, which occurs in GCH-1-deficient DRD. Surprisingly, this patient presented no dystonia or GCH-1 gene mutation or deletion. This case suggests that low pterin metabolism should be considered in older-onset levodopa-responsive parkinsonism with normal DAT-SPECT, even without GCH-1 mutations or deletions.