Commentary: Juvenile Dystonia‐Parkinsonism due to <scp><i>DNAJC6</i></scp> Mutation

This interesting case report by Garza-Brambila et al1 describes an 11-year-old girl presenting delayed motor development as early as 16 months of age and parkinsonian signs from the age of 8 years, initially responding to dopaminergic therapy. The case video presents a patient with a clinical syndrome of dystonia-parkinsonism characterized by bilateral bradykinesia, reduced facial expression, resting tremor of the hands, and dystonia involving the neck, upper and lower limbs. The latter mainly consisted in the plantar flexion of the foot, which can resemble the so-called “cock-walk” seen in patients with acquired or inherited forms of manganism. However, this patient lacked the characteristic compensatory excessive hip flexion seen in cock-walk. In addition, this patient also showed significant cognitive impairment detected through neurocognitive assessment. Brain magnetic resonance imaging (MRI) and laboratory test results were normal. In our opinion, the most important features for establishing a diagnosis in this case include early-onset dystonia-parkinsonism syndrome, cognitive impairment, and response to levodopa treatment. In fact, given this patient's clinical presentation, there is a wide range of possible differential diagnoses that should be considered including several rare conditions such as pediatric neurotransmitter disorders (Table 1).2 However, she does not show oculogyric crisis and dysautonomia, which are very common manifestations in primary neurotransmitter disorders. When we mention forms of juvenile parkinsonism or dystonia-parkinsonism responsive to levodopa, we should also consider genetic causes of monogenic Parkinson's disease (PD). This group of disorders includes mutations of known genes such as PRKN and PINK1, and more recently described genes such as SYNJ1 and DNAJC6, which also feature a good response to levodopa. The definite diagnosis for this case was DNAJC6 gene mutation, an emerging cause of recessive juvenile dystonia-parkinsonism that should be considered in the differential diagnosis of pediatric neurotransmitter disorders, especially in those presenting with low levels of homovanilic acid.3, 4 (1) Research Project: A. Conception, B. Organization, C. Execution; (2) Statistical Analysis: A. Design, B. Execution, C. Review and Critique; (3) Manuscript Preparation: A. Writing of the First Draft, B. Review and Critique. O.G.P.B.: 1A, 1B, 1C, 3A D.G.B.: 1A, 1B, 1C C.N.E.H.: 1A, 1B, 1C J.R.Z.: 1A, 1B, 1C D.M.R.: 1A, 1B, 1C A.F.: 3A, 3B The authors confirm that neither informed patient consent nor the approval of an institutional review board was necessary for this work. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines. There are no funding sources or conflicts of interest related to this case. D.M.R. received support linked to consultancies from UCB Mexico and speaker honoraria from Abbott unrelated to this research. A.F. received honoraria from AbbVie, Abbott, Boston Scientific, Ceregate, Ipsen, Integra, Medtronic, and UCB and research support from AbbVie, Boston Scientific and Medtronic.

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