Bridging the Gap: Gene Therapy in a Patient With Spinal Muscular Atrophy Type 1.

Molecular therapies exploit the understanding of pathogenic mechanisms to reconstitute impaired gene function or manipulate flawed RNA expression. These therapies include (1) RNA interference by antisense oligonucleotides, (2) mRNA modification using small molecules, and (3) gene replacement therapy, the viral-mediated intracellular delivery of exogenous nucleic acids to reverse a genetic defect. Several molecular therapies are approved for treating spinal muscular atrophy (SMA), a recessive genetic disorder caused by survival motor neuron (SMN)1 gene alterations. SMA involves degeneration of lower motor neurons, which leads to progressive muscle weakness, hypotonia, and hypotrophy. Onasemnogene abeparvovec is a gene replacement therapy for SMA that uses adeno-associated virus delivery of functional SMN1 cDNA to motor neurons. Two other molecular therapies modulate SMN2 transcription: nusinersen, an antisense oligonucleotide, and risdiplam, a small molecule designed to modify faulty mRNA expression. The most suitable individualized treatment for SMA is not established. Here, we describe remarkable clinical improvement in a 4-month-old patient with SMA type 1 who received onasemnogene abeparvovec therapy. This case represents an explanatory bridge from bench to bedside with regard to therapeutic approaches for genetic disorders in neurology. Knowledge of the detailed mechanisms underlying genetic neurologic disorders, particularly monogenic conditions, is paramount for developing tailored therapies. When multiple disease-modifying therapies are available, early genetic diagnosis is crucial for appropriate therapy selection, highlighting the importance of early identification and intervention. A combination of drugs, each targeting unique genetic pathomechanisms, may provide additional clinical benefits.

Refractory Seizures Secondary to Vitamin B6 Deficiency in Parkinson Disease: The Role of Carbidopa-Levodopa.

Carbidopa-levodopa has been used for more than 50 years in the treatment of Parkinson disease (PD) and other movement disorders. Pyridoxal 5'-phosphate (PLP), an active form of vitamin B6 (pyridoxine), is involved in the decarboxylation of levodopa to dopamine; carbidopa, which is combined with levodopa to reduce peripheral levodopa conversion and minimize peripheral dopamine side effects, binds irreversibly with PLP. As a result, carbidopa-levodopa may cause vitamin B6 deficiency and associated sequelae, including seizures, especially in high doses. A 78-year-old gentleman with a 6-year history of PD on carbidopa-levodopa therapy and recent weight loss presented with new-onset myoclonus and focal to bilateral tonic-clonic seizures. Workup for vascular, infectious, malignant, metabolic, and autoimmune causes of seizure was unrevealing. The folate level was critically low at <2.20 ng/dL. Video EEG studies showed moderate cerebral dysfunction and seizures with diffuse onsets. Several anti-seizure medications (ASMs) were unsuccessfully tried, so empiric treatment with high-dose steroids was initiated eventually alongside intravenous vitamin B6 therapy. Following introduction of these interventions, the patient had no further epileptic events. The vitamin B6 level came back as undetectable at <1 µg/dL. The patient was discharged to a rehabilitation center for improved strength and function. At the time of writing, he remained on two ASMs as well as IV B6 supplementation. Vitamin B6 is a required cofactor in the decarboxylation of levodopa to dopamine, and high levodopa dosages may cause B6 deficiency; in addition, carbidopa binds B6 irreversibly. We recommend screening of vitamin B6 levels in PD patients, especially those requiring high or increasing doses of carbidopa-levodopa and those with poor nutrition.

Genetics of cognitive dysfunction in Parkinson's disease.

Presentation and progression of cognitive symptoms in Parkinson's disease are highly variable. PD is a genetically complex disorder with multiple genetic risk factors and understanding the role that genes play in cognitive outcomes is important for patient counseling and treatment. Currently, there are seven well-described genes that increase the risk for PD, with variable levels of penetrance: SNCA, LRRK2, VPS35, PRKN, PINK1, DJ1 and GBA. In addition, large, genome-wide association studies have identified multiple loci in our DNA which increase PD risk. In this chapter, we summarize what is currently known about each of the seven strongly-associated PD genes and select PD risk variants, including PITX3, TMEM106B, SNCA Rep1, APOɛ4, COMT and MAPT H1/H1, along with their respective relationships to cognition.

Parkinson's disease prevalence in Fabry disease: A survey study.

Recent research has suggested a possible link between Parkinson's disease (PD) and Fabry disease. To test this relationship, we administered a self-report and family history questionnaire to determine the prevalence of PD in Fabry disease patients and family members with likely pathogenic alpha-galactosidase A (GLA) mutations. A total of 90 Fabry patients (77 from the online survey and 13 from the Icahn School of Medicine at Mount Sinai (ISMMS)) were included in the analysis. Two of the Fabry disease patients who completed the online survey were diagnosed with PD (2/90, 2.2%). Among probands older than 60, 8.3% (2/24) were diagnosed with PD. Using Kaplan Meier survival analysis, the age-specific risk of PD by age 70 was 11.1%. Family history was available on 72 Fabry families from the online study and 9 Fabry families from ISMMS. Among these 81 families, 6 (7.4%) had one first degree relative who fit the criteria for a conservative diagnosis of PD. The results of this study suggest that there may be an increased risk of developing PD in individuals with GLA mutations, but these findings should be interpreted with caution given the limitations of the study design.

Essential tremor-Parkinson's disease: A double whammy.

BACKGROUND: Surprisingly little has been written about the combined clinical entity, essential tremor-Parkinson's disease (ET-PD), which is the result of a double disease hit. We carefully quantified tremor burden using a wide range of measures (tremor severity, tremor-related disability, tremor-related quality of life) and furthermore, studied additional motor and non-motor features in ET-PD. METHODS: In this prospective, clinical-epidemiological study, we performed a standardized, structured clinical evaluation of 27 ET-PD patients, comparing them to age-matched samples of 35 PD and 109 ET patients. RESULTS: The number of hours/day shaking was lowest in PD (median=3.0), intermediate in ET (median=10.0) and highest in ET-PD (median=14.0) (p<0.001). All measures of mobility and balance (Berg Balance test, Activities-specific Balance Confidence Scale, Timed Up and Go test) worsened across groups in a stepwise manner from ET to PD to ET-PD (p<0.05). Mini-mental state test scores worsened (p=0.002) and daytime sleepiness increased (p=0.002) across groups from ET to PD to ET-PD. CONCLUSIONS: The ET-PD patient seems to be more than just a PD patient with a little more kinetic tremor. Aside from a significantly greater tremor burden, ET-PD patients exhibited more cognitive and sleep problems and more mobility and balance problems than patients with isolated PD.