High diagnostic yield and novel variants in very late-onset spasticity

Primary Lateral Sclerosis: An Overview

Primary lateral sclerosis (PLS) is a rare neurodegenerative disorder which causes the selective deterioration of the upper motor neurons (UMNs), sparing the lower motor neuron (LMN) system. The clinical course is defined by a progressive motor disability due to muscle spasticity which typically involves lower extremities and bulbar muscles. Although classically considered a sporadic disease, some familiar cases and possible causative genes have been reported. Despite it having been recognized as a rare but distinct entity, whether it actually represents an extreme end of the motor neuron diseases continuum is still an open issue. The main knowledge gap is the lack of specific biomarkers to improve the clinical diagnostic accuracy. Indeed, the diagnostic imprecision, together with some uncertainty about overlap with UMN-predominant ALS and Hereditary Spastic Paraplegia (HSP), has become an obstacle to the development of specific therapeutic trials. In this study, we provided a comprehensive analysis of the existing literature, including neuropathological, clinical, neuroimaging, and neurophysiological features of the disease, and highlighting the controversies still unsolved in the differential diagnoses and the current diagnostic criteria. We also discussed the current knowledge gaps still present in both diagnostic and therapeutic fields when approaching this rare condition.

Power of NGS-based tests in HSP diagnosis: analysis of massively parallel sequencing in clinical practice

Hereditary spastic paraplegia (HSP) refers to a group of heterogeneous neurological disorders mainly characterized by corticospinal degeneration (pure forms), but sometimes associated with additional neurological and extrapyramidal features (complex HSP). The advent of next-generation sequencing (NGS) has led to huge improvements in knowledge of HSP genetics and made it possible to clarify the genetic etiology of hundreds of "cold cases," accelerating the process of reaching a molecular diagnosis. The different NGS-based strategies currently employed as first-tier approaches most commonly involve the use of targeted resequencing panels and exome sequencing, whereas genome sequencing remains a second-tier approach because of its high costs. The question of which approach is the best is still widely debated, and many factors affect the choice. Here, we aim to analyze the diagnostic power of different NGS techniques applied in HSP, by reviewing 38 selected studies in which different strategies were applied in different-sized cohorts of patients with genetically uncharacterized HSP.

Primary lateral sclerosis

Like motor neuron diseases (MNDs) refer to a constellation of primarily sporadic neurodegenerative diseases characterized by a progressive loss of upper and/or lower motor neurons. Primary lateral sclerosis (PLS) is considered a neurodegenerative disorder that is characterized by a gradually progressive course affecting the central motor systems, designated by the phrase "upper motor neurons." Despite significant development in neuroimaging, neurophysiology, and molecular biology, there is a growing consensus that PLS is of unknown etiology. Currently there is no disease-modifying treatment for PLS, or prospective randomized trials being carried out, partly due to the rarity of the disease and lack of significant understanding of the underlying pathophysiology. Consequently, the approach to treatment remains largely symptomatic. In this chapter we provide an overview of primary lateral sclerosis including clinical and electrodiagnostic considerations, differential diagnosis, updates in genetics and pathophysiology, and future directions for research.

The Cure VCP Scientific Conference 2021: Molecular and clinical insights into neurodegeneration and myopathy linked to multisystem proteinopathy-1 (MSP-1)

The 2021 VCP Scientific Conference took place virtually from September 9–10, 2021. This conference, planned and organized by the nonprofit patient advocacy group Cure VCP Disease, Inc. (https://www.curevcp.org), was the first VCP focused meeting since the 215th ENMC International Workshop VCP-related multi-system proteinopathy in 2016 (Evangelista et al., 2016). Mutations in VCP cause a complex and heterogenous disease termed inclusion body myopathy (IBM) with Paget’s disease of the bone (PDB) and frontotemporal dementia (FTD) (IBMPFD), or multisystem proteinopathy 1 (MSP-1) Kimonis (n.d.), Kovach et al. (2001), Kimonis et al. (2000). In addition, VCP mutations also cause other age-related neurodegenerative disorders including amyptrophic lateral sclerosis (ALS), Parkinsonism, Charcot-Marie type II-B, vacuolar tauopathy among others (Korb et al., 2022). The objectives of this conference were as follows: (1) to provide a forum that facilitates sharing of published and unpublished information on physiological roles of p97/VCP, and on how mutations of VCP lead to diseases; (2) to bolster understanding of mechanisms involved in p97/VCP-relevant diseases and to enable identification of therapeutics to treat these conditions; (3) to identify gaps and barriers of further discoveries and translational research in the p97/VCP field; (4) to set a concrete basic and translational research agenda for future studies including crucial discussions on biomarker discoveries and patient longitudinal studies to facilitate near-term clinical trials; (5) to accelerate cross-disciplinary research collaborations among p97/VCP researchers; (6) to enable attendees to learn about new tools and reagents with the potential to facilitate p97/VCP research; (7) to assist trainees in propelling their research and to foster mentorship from leaders in the field; and (8) to promote diversity and inclusion of under-represented minorities in p97/VCP research as diversity is critically important for strong scientific research. Given the range of topics, the VCP Scientific Conference brought together over one hundred and forty individuals representing a diverse group of research scientists, trainees, medical practitioners, industry representatives, and patient advocates. Twenty-five institutions with individuals from thirteen countries attended this virtual meeting. In this report, we summarize the major topics presented at this conference by a range of experts.

Anticipation Can Be More Common in Hereditary Spastic Paraplegia with SPAST Mutations Than It Appears

BACKGROUND AND OBJECTIVE

Hereditary spastic paraplegia (HSP) is a heterogeneous neurodegenerative disorder with lower-limb spasticity and weakness. Different patterns of inheritance have been identified in HSP. Most autosomal-dominant HSPs (AD-HSPs) are associated with mutations of the SPAST gene (SPG4), leading to a pure form of HSP with variable age-at-onset (AAO). Anticipation, an earlier onset of disease, as well as aggravation of symptoms in successive generations, may be correlated to SPG4. Herein, we suggested that anticipation might be a relatively common finding in SPG4 families.

METHODS

Whole-exome sequencing was done on DNA of 14 unrelated Iranian AD-HSP probands. Data were analyzed, and candidate variants were PCR-amplified and sequenced by the Sanger method, subsequently checked in family members to co-segregation analysis. Multiplex ligation-dependent probe amplification (MLPA) was done for seven probands. Clinical features of the probands were recorded, and the probable anticipation was checked in these families. Other previous reported SPG4 families were investigated to anticipation.

RESULTS

Our findings showed that SPG4 was the common subtype of HSP; three families carried variants in the KIF5A, ATL1, and MFN2 genes, while five families harbored mutations in the SPAST gene. Clinical features of only SPG4 families indicated decreasing AAO in affected individuals of the successive generations, and this difference was significant (p-value <0.05).

CONCLUSION

It seems SPAST will be the first candidate gene in families that manifests a pure form of AD-HSP and anticipation. Therefore, it may be a powerful situation of genotype-phenotype correlation. However, the underlying mechanism of anticipation in these families is not clear yet.

Case Report: Calpainopathy Presenting After Bone Marrow Transplantation, With Studies of Donor Genetic Content in Various Tissue Types

We present a patient who had two allogeneic bone marrow transplantations for acute lymphocytic leukemia. She developed slowly progressive limb-girdle weakness in the context of other symptoms of graft-vs.-host disease (GVHD). Her myopathy symptoms had been initially attributed to GVHD, but when she progressed despite immunotherapy, genetic testing was requested. Initial testing was performed on a blood sample, identifying a variant of unknown significance in DMD. Subsequent testing of DNA from the patient's muscle tissue identified two pathogenic variants in CAPN3, with absence of the DMD variant (this latter variant presumed to have been received from the donor). Allele-specific digital droplet qPCR permitted the quantification of the donor variant in various tissues from the patient (whole skin, isolated fibroblasts, whole blood, saliva, buccal cells, urine sediment, and two muscle biopsies taken at a 2 year interval). This report emphasizes that genetic disease should still be considered in the context of presumably acquired disease, and also demonstrates the extent of transdifferentiation of donor cells into other tissues.