Embracing Monogenic Parkinson's Disease: The MJFF Global Genetic PD Cohort

BACKGROUND

As gene-targeted therapies are increasingly being developed for Parkinson's disease (PD), identifying and characterizing carriers of specific genetic pathogenic variants is imperative. Only a small fraction of the estimated number of subjects with monogenic PD worldwide are currently represented in the literature and availability of clinical data and clinical trial-ready cohorts is limited.

OBJECTIVE

The objectives are to (1) establish an international cohort of affected and unaffected individuals with PD-linked variants; (2) provide harmonized and quality-controlled clinical characterization data for each included individual; and (3) further promote collaboration of researchers in the field of monogenic PD.

METHODS

We conducted a worldwide, systematic online survey to collect individual-level data on individuals with PD-linked variants in SNCA, LRRK2, VPS35, PRKN, PINK1, DJ-1, as well as selected pathogenic and risk variants in GBA and corresponding demographic, clinical, and genetic data. All registered cases underwent thorough quality checks, and pathogenicity scoring of the variants and genotype-phenotype relationships were analyzed.

RESULTS

We collected 3888 variant carriers for our analyses, reported by 92 centers (42 countries) worldwide. Of the included individuals, 3185 had a diagnosis of PD (ie, 1306 LRRK2, 115 SNCA, 23 VPS35, 429 PRKN, 75 PINK1, 13 DJ-1, and 1224 GBA) and 703 were unaffected (ie, 328 LRRK2, 32 SNCA, 3 VPS35, 1 PRKN, 1 PINK1, and 338 GBA). In total, we identified 269 different pathogenic variants; 1322 individuals in our cohort (34%) were indicated as not previously published.

CONCLUSIONS

Within the MJFF Global Genetic PD Study Group, we (1) established the largest international cohort of affected and unaffected individuals carrying PD-linked variants; (2) provide harmonized and quality-controlled clinical and genetic data for each included individual; (3) promote collaboration in the field of genetic PD with a view toward clinical and genetic stratification of patients for gene-targeted clinical trials. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Neurophysiological study in a Spanish family with recessive spastic ataxia of Charlevoix-Saguenay

In order to characterize the electrodiagnostic features of autosomal-recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) more fully, we report the clinical and neurophysiological findings in two patients from a Spanish pedigree with a homozygous missense point mutation in the SACS gene. Nerve conduction studies showed signs of both axonal and demyelinating neuropathy. In the upper-limb nerves, motor conduction velocity was intermediately slowed. Sensory nerve action potentials were attenuated or absent. In addition, slowed conduction in the central motor, somatosensory, and auditory brainstem pathways was observed, and masseter and blink reflexes were abnormal. As a whole, this constellation of electrophysiological findings helps in the diagnosis of ARSACS.

Stability of erythropoietin repackaging in polypropylene syringes for clinical use

Introduction: Epoetin alfa (Eprex®) is a subcutaneous, injectable formulation of short half-life recombinant human erythropoietin (rHuEPO). To current knowledge there are no published studies regarding the stability of rHuEPO once repackaging occurs (r-EPO) for clinical trial purposes. Materials and methods: We assessed EPO concentration in Eprex® and r-EPO syringes at 0, 60, 90, and 120 days after repackaging in polypropylene syringes. R-EPO was administered to 56 patients taking part in a clinical trial in Friedreich Ataxia. Serum EPO levels were measured at baseline and 48 h after r-EPO administration. Results: No differences were found between r-EPO and Eprex® syringes, but both globally decreased in total EPO content during storage at 4 °C. Patients receiving r-EPO had similar levels in EPO content as expected from previous trials in Friedreich Ataxia and from pharmacokinetics studies in healthy volunteers. Discussion: We demonstrate that repackaging of EPO does not alter its concentration if compared to the original product (Eprex®). This is true both for repackaging procedures and for the stability in polypropylene tubes. The expiration date of r-EPO can be extended from 1 to 4 months after repackaging, in accordance with pharmacopeia rules.

Measuring cognitive impairment and monitoring cognitive decline in Huntington's disease: a comparison of assessment instruments

BACKGROUND

Progressive cognitive decline is an inevitable feature of Huntington's disease (HD) but specific criteria and instruments are still insufficiently developed to reliably classify patients into categories of cognitive severity and to monitor the progression of cognitive impairment.

METHODS

We collected data from a cohort of 180 positive gene-carriers: 33 with premanifest HD and 147 with manifest HD. Using a specifically developed gold-standard for cognitive status we classified participants into those with normal cognition, those with mild cognitive impairment, and those with dementia. We administered the Parkinson's Disease-Cognitive Rating Scale (PD-CRS), the MMSE and the UHDRS cogscore at baseline, and at 6-month and 12-month follow-up visits. Cutoff scores discriminating between the three cognitive categories were calculated for each instrument. For each cognitive group and instrument we addressed cognitive progression, sensitivity to change, and the minimally clinical important difference corresponding to conversion from one category to another.

RESULTS

The PD-CRS cutoff scores for MCI and dementia showed excellent sensitivity and specificity ratios that were not achieved with the other instruments. Throughout follow-up, in all cognitive groups, PD-CRS captured the rate of conversion from one cognitive category to another and also the different patterns in terms of cognitive trajectories.

CONCLUSION

The PD-CRS is a valid and reliable instrument to capture MCI and dementia syndromes in HD. It captures the different trajectories of cognitive progression as a function of cognitive status and shows sensitivity to change in MCI and dementia.