Distonías primarias respondedoras a levodopa (DRD): búsqueda sistemática en Latinoamérica / Dopa-responsive dystonia (DRD): systematic search in Latin America

RESUMEN Las distonías que responden a levodopa (DRD, siglas en inglés) abarcan un grupo de distonías primarias, causadas por deficiencias enzimáticas en la vía metabólica de las aminas y, por definición, comparten como característica principal su respuesta favorable y sostenida a levodopa. Existen hasta seis genes asociados a DRD, siendo el gen GCH1 el más frecuentemente involucrado. La presentación típica de esta entidad se caracteriza por su aparición en la niñez, distonía de inicio en miembros inferiores con fluctuación diurna, leve parkinsonismo y respuesta clara a dosis bajas de levodopa. Se incluye una búsqueda sistemática de la literatura con casos de DRD publicados en Latinoamérica.

SUMMARY Dopa-responsive dystonia (DRD) encompasses a heterogenous group of primary dystonias, caused by enzymatic deficiencies across the amines pathway and, by definition, show as their main characteristic a favorable and sustained response to levodopa. There are up to 6 genes associated with DRD, including pathogenic variants of the GCH1 gene as the most frequently involved. The typical presentation of DRD is characterized by start in childhood, lower limb-onset dystonia with daytime fluctuation, mild parkinsonism, and a sustained response to low doses of levodopa. A systematic literature search on DRD reported cases in Latin America is presented.

Expanding the Spectrum of Dopa-Responsive Dystonia (DRD) and Proposal for New Definition: DRD, DRD-plus, and DRD Look-alike

Previously, we defined DRD as a syndrome of selective nigrostriatal dopamine deficiency caused by genetic defects in the dopamine synthetic pathway without nigral cell loss. DRD-plus also has the same etiologic background with DRD, but DRD-plus patients have more severe features that are not seen in DRD because of the severity of the genetic defect. However, there have been many reports of dystonia responsive to dopaminergic drugs that do not fit into DRD or DRD-plus (genetic defects in the dopamine synthetic pathway without nigral cell loss). We reframed the concept of DRD/DRD-plus and proposed the concept of DRD look-alike to include the additional cases described above. Examples of dystonia that is responsive to dopaminergic drugs include the following: transportopathies (dopamine transporter deficiency; vesicular monoamine transporter 2 deficiency); SOX6 mutation resulting in a developmentally decreased number of nigral cells; degenerative disorders with progressive loss of nigral cells (juvenile Parkinson's disease; pallidopyramidal syndrome; spinocerebellar ataxia type 3), and disorders that are not known to affect the nigrostriatal dopaminergic system (DYT1; GLUT1 deficiency; myoclonus-dystonia; ataxia telangiectasia). This classification will help with an etiologic diagnosis as well as planning the work up and guiding the therapy.

A Case of Dopa-Responsive Dystonia, Segawa Disease / 대한소아신경학회지

Segawa disease, hereditary progressive dystonia with marked diurnal fluctuations or defined dopa-responsive dystonia has age-dependent clinical courses, which are characterized with marked progression in the first one and half decades, its subsiding in the third decade and almost stationary courses after the fourth decade. Also, it has characteristic diurnally fluctuating symptoms, aggravated towards the evening and alleviated after sleep. This autosomally dominantly inherited dystonia is caused by abnormalities of the gene of GTP cyclohydrolase I. The heterozygotic gene's abnormality induces partial decrement of tetrahydrobiopterin and affects synthesis of tyrosine hydroxylase(TH) rather selectively. The reduction of TH induces decrement of dopamine and disfacilitates the D1 receptor-striatal direct pathway. The pathognomonic finding in biochemical examination is the decrease of neopterin in the cerebrospinal fluid(CSF). Levodopa, by replacing dopamine contents at the terminal, alleviates motor symptoms completely and the effects sustain without any side effects. We experienced a girl diagnosed as Segawa disease with typical clinical courses and a decrease of neopterin in the CSF.