Primary lateral sclerosis and hereditary spastic paraplegia in sporadic patients. An important distinction in descriptive studies

Presenilin-1 Mutations Are a Cause of Primary Lateral Sclerosis-Like Syndrome

Background and Purpose

Primary lateral sclerosis (PLS) is a progressive upper motor neuron (UMN) disorder. It is debated whether PLS is part of the amyotrophic lateral sclerosis (ALS) spectrum, or a syndrome encompassing different neurodegenerative diseases. Recently, new diagnostic criteria for PLS have been proposed. We describe four patients of two pedigrees, meeting definite PLS criteria and harboring two different mutations in presenilin 1 (PSEN1).

Methods

Patients underwent neurological and neuropsychological examination, MRI, 18F-fluorodeoxyglucose positron emission tomography (FDG-PET), amyloid-related biomarkers, and next-generation sequencing (NGS) testing.

Results

Four patients, aged 25–45 years old, presented with a progressive UMN syndrome meeting clinical criteria of definite PLS. Cognitive symptoms and signs were mild or absent during the first year of the disease but appeared or progressed later in the disease course. Brain MRI showed microbleeds in two siblings, but iron-related hypointensities in the motor cortex were absent. Brain FDG-PET showed variable areas of hypometabolism, including the motor cortex and frontotemporal lobes. Amyloid deposition was confirmed with either cerebrospinal fluid (CSF) or imaging biomarkers. Two heterozygous likely pathogenic mutations in PSEN1 (p.Pro88Leu and p.Leu166Pro) were found in the NGS testing.

Conclusion

Clinically defined PLS is a syndrome encompassing different neurodegenerative diseases. The NGS testing should be part of the diagnostic workup in patients with PLS, at least in those with red flags, such as early-onset, cognitive impairment, and/or family history of neurodegenerative diseases.

Challenges and Controversies in the Genetic Diagnosis of Hereditary Spastic Paraplegia

Purpose of Review

The hereditary spastic paraplegias (HSPs) are a group of disorders characterised by progressive lower limb weakness and spasticity. We address the challenges and controversies involved in the genetic diagnosis of HSP.

Recent Findings

There is a large and rapidly expanding list of genes implicated in HSP, making it difficult to keep gene testing panels updated. There is also a high degree of phenotypic overlap between HSP and other disorders, leading to problems in choosing the right panel to analyse. We discuss genetic testing strategies for overcoming these diagnostic hurdles, including the use of targeted sequencing gene panels, whole-exome sequencing and whole-genome sequencing. Personalised treatments for HSP are on the horizon, and a genetic diagnosis may hold the key to access these treatments.

Summary

Developing strategies to overcome the challenges and controversies in HSP may hold the key to a rapid and accurate genetic diagnosis.

What's in the Literature?

The Guillain-Barré syndrome (GBS) is one of the few neuropathies well known to the general public, in part because of its association with swine flu vaccinations in 1976. GBS has again reached the general public with its possible association with Zika virus. The virus, borne by infected Aedes aegypti mosquitos, is being linked to birth defects when pregnant women are bitten and infected. There are early reports also linking GBS to Zika infection, which could expose a wider range of infected people to the neuropathy. This summer infected Aedes mosquitos will likely reach southern portions of the United States, and travelers to countries where Aedes is endemic will increase. It is important to appreciate that the neurologic consequences of Zika virus are being actively investigated, and firm associations and consequences are yet to be established. Small fiber neuropathies are common and can be due to a number of underlying diseases, and a recent review also indicates that many are idiopathic. One cause is Sjögren syndrome, and a case series reviews clinical features. The diagnosis and underlying features of primary lateral sclerosis are a clinical challenge. Similarities between primary lateral sclerosis and hereditary spastic paraparesis (HSP) have long been noted. With a wide spectrum of gene mutations associated with HSP, clinical distinction between the 2 disorders is problematic. A review covers the wide spectrum of HSP. With no cure, the progression of amyotrophic lateral sclerosis (ALS) to respiratory failure is predictable. This could easily result in marked depression among patients, and 2 studies have explored the frequency and severity of depression. The cause of ALS remains unknown, and when no hereditary factor is apparent, environmental questions arise as possible contributing factor(s). The most notable association is with military service, although specific occupational or environmental linkages are not well sorted out. Two recent reports address these issues. There is good news for ALS patients with muscle cramps with the results of a multicenter randomized and placebo-controlled trial showing that mexiletine is effective in reducing this common symptom. The treatment of myasthenia gravis with various agents, the use of patient-reported outcome measures in myasthenia gravis, and the occurrence of myocarditis in this disease are reviewed. Necrotizing autoimmune neuropathies, the co-occurrence of inclusion body myositis and a form of T-cell leukemia are discussed as are valosin-containing protein (VCP)-opathy and bone health in patients with dystrophinopathy.