DNAJC12 Disease: Clinical Spectrum and Long-Term Outcomes

Background and ObjectivesAutosomal recessive DNAJC12 disease, the most recently identified disorder of biogenic amine synthesis, presents with a broad clinical spectrum and variable outcomes, ranging from asymptomatic patients to early-onset parkinsonism. This study aimed to better outline the clinical phenotype and outcomes of DNAJC12 disease, the prognostic value of the metabolic and genetic biomarkers, and the treatment response.MethodsWe systematically collected clinical, biochemical, and genetic data from 56 patients with DNAJC12 disease in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines: 51 from the literature since the disease was first described and 5 unpublished personal cases.ResultsThree prevalent clinical patterns of presentation and outcome were identified: (1) asymptomatic condition, (2) neurodevelopmental disorders (NDD) leading to intellectual disability with psychiatric issues and dystonia-parkinsonism (D-P) during the second decade of life in some patients, and (3) early-onset static l-dopa-responsive parkinsonism in previously asymptomatic adult patients. Hyperphenylalaninemia was the most consistent metabolic alteration. CSF depletion of homovanillic acid (HVA) and 5-HIAA was detected in 18 and 20 of 29 symptomatic patients, respectively. Three stepwise regression analyses identified significant predictors of clinical outcomes in patients with phenylketonuria (PKU). CSF HVA levels and phenylalanine levels at diagnosis predicted the occurrence of D-P, while 26% of intellectual disability variability was explained by CSF HVA at diagnosis, and 31% of psychiatric disorder variability by later age at diagnosis. The phenotype was consistently associated with only a few DNAJC12 pathogenic variants, primarily for phenotypes A and C.Movement disorders responded positively to the various therapies in all symptomatic patients. The preventive effects on NDD and psychiatric problems were less clear.ResultsThree prevalent clinical patterns of presentation and outcome were identified: (1) asymptomatic condition, (2) neurodevelopmental disorders (NDD) leading to intellectual disability with psychiatric issues and dystonia-parkinsonism (D-P) during the second decade of life in some patients, and (3) early-onset static l-dopa-responsive parkinsonism in previously asymptomatic adult patients. Hyperphenylalaninemia was the most consistent metabolic alteration. CSF depletion of homovanillic acid (HVA) and 5-HIAA was detected in 18 and 20 of 29 symptomatic patients, respectively. Three stepwise regression analyses identified significant predictors of clinical outcomes in patients with phenylketonuria (PKU). CSF HVA levels and phenylalanine levels at diagnosis predicted the occurrence of D-P, while 26% of intellectual disability variability was explained by CSF HVA at diagnosis, and 31% of psychiatric disorder variability by later age at diagnosis. The phenotype was consistently associated with only a few DNAJC12 pathogenic variants, primarily for phenotypes A and C.Movement disorders responded positively to the various therapies in all symptomatic patients. The preventive effects on NDD and psychiatric problems were less clear.DiscussionDNAJC12 disease is a new metabolic neurodevelopmental disorder linked to parkinsonism. The combined effects of neurotransmitter depletion and disrupted enzyme proteostasis in dopaminergic and serotoninergic neurons may underlie the early neurodevelopmental presentation and subsequent neurologic and psychiatric disorders.