Dopa-responsive dystonia, DRD-plus and DRD look-alike: a pragmatic review

Chloroprocaine 3% for anesthesia during cesarean section in a patient with dopa-responsive dystonia: A case report

RATIONALE

Dopa-responsive dystonia (DRD) is a rare autosomal dominant hereditary disorder with a prevalence of 0.5 per million population. The disease is characterized by onset of dystonia in childhood, progressive aggravation of the dystonia with diurnal fluctuation, and complete or near complete alleviation of symptoms with low-dose oral levodopa. The incidence of DRD is low, and only a few publications have described this disorder connected with anesthesia.

PATIENT CONCERNS

We present a case involving a pregnant woman with DRD who continued levodopa/benserazide throughout the pregnancy. The perioperative anesthesia management was described. We used chloroprocaine 3% for epidural anesthesia during cesarean section.

DIAGNOSES

Dopa-responsive dystonia.

INTERVENTIONS

Levodopa/benserazide.

OUTCOMES

In summary, levodopa/benserazide was continued throughout our patient's pregnancy with a good obstetric outcome, and chloroprocaine was safely used in epidural anesthesia without deterioration of her dystonic symptoms.

LESSONS

Chloroprocaine was safely used in epidural anesthesia without deterioration of her dystonic symptoms.

Establishment of a non-integrated iPSC (SDQLCHi066-A) line derived from Segawa syndrome patients harboring heterozygous mutations in the TH gene (p.G247S and p.D491H)

Segawa syndrome, an autosomal recessive genetic disorder, arises from homozygous or compound heterozygous mutations in the TH gene. We established an induced pluripotent stem cell (iPSC) line from peripheral blood mononuclear cells (PBMCs) of an 4-month-old girl with Segawa syndrome, who carried compound heterozygous mutations of c.739G > A/chr11:2188714 and c.1471G > C/chr11:2185579 in TH. The iPSCs displayed a normal karyotype, expressed pluripotency markers, were devoid of genomically integrated episomal plasmids, and demonstrated trilineage differentiation potential in vitro.

The C886T Mutation in the Th Gene Reduces the Activity of Tyrosine Hydroxylase in the Mouse Brain

Tyrosine hydroxylase (TH) catalyzes hydroxylation of L-tyrosine to L-3,4-dihydroxyphenylalanine, the initial and rate-limiting step in the synthesis of dopamine, noradrenaline, and adrenaline. Mutations in the human TH gene are associated with hereditary motor disorders. The common C886T mutation identified in the mouse Th gene results in the R278H substitution in the enzyme molecule. We investigated the impact of this mutation on the TH activity in the mouse midbrain. The TH activity in the midbrain of Mus musculus castaneus (CAST) mice homozygous for the 886C allele was higher compared to C57BL/6 and DBA/2 mice homozygous for the 886T allele. Notably, this difference in the enzyme activity was not associated with changes in the Th gene mRNA levels and TH protein content. Analysis of the TH activity in the midbrain in mice from the F2 population obtained by crossbreeding of C57BL/6 and CAST mice revealed that the 886C allele is associated with a high TH activity. Moreover, this allele showed complete dominance over the 886T allele. However, the C886T mutation did not affect the levels of TH protein in the midbrain. These findings demonstrate that the C886T mutation is a major genetic factor determining the activity of TH in the midbrain of common laboratory mouse strains. Moreover, it represents the first common spontaneous mutation in the mouse Th gene whose influence on the enzyme activity has been demonstrated. These results will help to understand the role of TH in the development of adaptive and pathological behavior, elucidate molecular mechanisms regulating the activity of TH, and explore pharmacological agents for modulating its function.

The apparent paradox of phenotypic diversity and shared mechanisms across dystonia syndromes

PURPOSE OF REVIEW

We describe here how such mechanisms shared by different genetic forms can give rise to motor performance dysfunctions with a clinical aspect of dystonia.

RECENT FINDINGS

The continuing discoveries of genetic causes for dystonia syndromes are transforming our view of these disorders. They share unexpectedly common underlying mechanisms, including dysregulation in neurotransmitter signaling, gene transcription, and quality control machinery. The field has further expanded to include forms recently associated with endolysosomal dysfunction.

SUMMARY

The discovery of biological pathways shared between different monogenic dystonias is an important conceptual advance in the understanding of the underlying mechanisms, with a significant impact on the pathophysiological understanding of clinical phenomenology. The functional relationship between dystonia genes could revolutionize current dystonia classification systems, classifying patients with different monogenic forms based on common pathways. The most promising effect of these advances is on future mechanism-based therapeutic approaches.

Mitofusin 2: The missing link between mtDNA maintenance defects and neurotransmitter disorders

Mitofusin (MFN) 2 belongs to the large family of mitochondrial transmembrane GTPases and has a role in dynamic mitochondrial remodeling process governed by fusion and fission. MFN2 pathogenic variants classically cause Charcot-Marie-Tooth disease type 2A (CMT2A), the most common axonal form of CMT, but patients with complex and unusual phenotypes involving the central and peripheral nervous system have been described, with mitochondrial dysfunction proposed as the underlying pathogenic mechanism. Here, we report the first description of a neurochemical pattern of secondary alterations in the metabolism of biogenic amines linked to the de novo presence of the hotspot MFN2 pathogenic variant p.Arg104Trp. The infant presented a very early onset choreic movement disorder associated with severe axial hypotonia and fluctuating dystonia of limbs. The relationship between mitochondrial DNA (mtDNA) maintenance defects and dopaminergic neurotransmitter disorders, governed by MFN2, is discussed.