The Differences Between ALS And Muscular Dystrophy

In this blog post we will compare two conditions affecting our muscles. One is a neurodegenerative condition called Amyotrophic Lateral Scleorisis (ALS) and the other one is Muscular Dystrophy (MD). We will explore their differences, pathology, genetics and potential treatment.
Frederika Malichová

Frederika Malichová

Neuroscientist at the University Of Cambridge.

A blue image with text saying "ALS vs Muscular Dystrophy"

Differences Between ALS And Muscular Dystrophy

Although both ALS and MD are conditions affecting the neuromuscular system they differ in several ways. ALS affects primarily adults, while MD is a group of inherited diseases causing progressive muscle loss begining in childhood. The progression, symptoms, and treatment options for these two conditions also vary.

What Is ALS?

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease affecting the central nervous system.

The pathology of ALS is marked by a progressive buildup of protein aggregates. These protein inclusions are formed from proteins like TDP-43, FUS, or SOD1 proteins [1, 2]. As the accumulation progresses these builtups lead to the loss of motor neurons in the cortex, brain stem and spinal cord.

In addition to protein aggregation, ALS patients shows signs of axonal degeneration and destruction of nerve terminals [3].

Symptoms of ALS are devastating. The patients quickly lose their ability to control muscle movement and are often wheel-chair dependent or bed-bound. Unfortunately, the patients usually die after 3-5 years of the symptom onset [4, 5].

ALS can come in different forms. One form of amyotrophic lateral sclerosis is bulbar onset ALS, where the symptoms begin with muscles around the face and neck.

What Is The Pathology Of ALS?

Another important aspect of ALS pathology is the role of RNA processing. Dysfunctional RNA processing, caused by mutations in RNA modulating genes such as TARDBP/TDP-43, FUS/TLS, or C9ORF72, is a significant contributor to disease pathogenesis [6].

Furthermore, recent studies suggest a prion-like propagation mechanism in ALS, where misfolded proteins spread from cell to cell, contributing to the progression of the disease [4].

What Is Muscular Dystrophy?

Muscular dystrophy (MD) refers to a group of conditions that progressively weaken and damage muscles over time.

MD is caused by mutations in the genes responsible for the structure and proper functioning of muscles. The gene mutations vary depending on the type of MD and even individuals with the same type of MD can have different gene mutation [7].

Duchenne MD, is on eof the most common type of MD and also the most severe one. It is caused by a mutation in the dystrophin gene. Interestingly, this type of MD occurs exclusively in males [8].

Another example of MD is adult onset MD. This one is caused by expanded number of trinucleotide repeats in the DMPK gene [9].

Clinical MD symptoms are muscle wekness, due to the loss of muscle tissue and strength.

There are different types of severity of MD and these types can vary for instance in the muscles that are being affected and the extent to which they are affected. In som etypes of MD, muscle sussed for breathing can be affected which can significantly impact life expectancy of the individual [10, 11, 12, 13].

What Is The Cause Of Muscular Dystrophy?

Muscular dystrophy is caused by mutations or alterations in the genes responsible for the structure and functioning of muscles. These genetic changes affect proteins that strengthen and protect muscles, leading to the symptoms of MD. The specific gene changes can vary for each type of MD, and even individuals with the same type of MD can have different gene mutations [7].

In addition, certain types of autosomal recessive limb-girdle muscular dystrophies are caused by a deficiency of sarcoglycan, a protein of the muscular membrane [13].

What Is The Genetics Of ALS And Muscular Dystrophy ?

ALS

ALS is usually a sporadic disease. Around 90% of all the cases are sporadic, meaning, they occur randomly, while 10% are being familial. These 10% of the cases indicate a clear genetic inheritance and usually occur due to transmitted mutations on genes SOD1 or C9orf72, GLT8D1 and others[14, 15].

Mutations in these genes can also cause other neurodegenerative diseases, such as genetically inherited frontotemporal dementia (FTD)

Muscular Dystrophy

MD is highly genetic disease. All types of MD are caused by genetic mutation on one of the major genes responsible for proper functioning and structure of muscles.

Let’s use medisearch to explore this more:

What Are The Possible Treatments For ALS And Muscular Dystrophy?

Both ALS and MD are incurable diseases, which typically consist of multidisciplinary approach in order to help manage the symptoms. All together, the treatments aim to manage symptoms, slow disease progression, and improve the patient's quality of life [16, 17].

ALS

The treatment options for ALS typically inculde psychological support, physical rehabilitation and Food and Drug Administration (FDA) approved pharmaceutical interventions.

Physical rehabilitation may consists of physical therapy but also speech therapy [16, 18, 19].

Medications helping to alleviate the symptoms of ALS are Riluzole and Edaravone [16, 18, 19].

Currently researched potential treatment options are gene therapy or cellular therapy, however these are yet to be considered [16, 18, 19].

Muscular Dystrophy

SImilarly to ALS, the treatment of MD consists of physical therapy, and pharmaceutical interventions.

There are several medications approved by the FDA for MD: Nusinersen (Spinraza), Onasemnogene abeparvovec-xioi (Zolgensma), Risdiplam (Evrysdi), Golodirsen (Vyondys 53), Viltolarsen (Viltepso), and Casimersen (Amondys 45)[17, 20, 21]..

In addition, corticosteroids and immunosuppressive drugs appear to slow muscle damage and drugs like phenytoin and mexiletine helping with muscle weakness can also be recommended [17, 20, 21].

What Are The Differences Between ALS And Muscular Dystrophy?

ALS and MD are both diseases affecting the ability to move. They are similar in the clinical manifestation and treatment options, however compeltely different when considering genetic factors, pathology and even disease progression.

While in ALS, we observe a progressive loss of motor neurons leading to muscle weakness, spasticity and muscle control, MD affects specific muscle groups in the body by improper structure and functioning of the muscles on molecular level resulting in muscle weakening and shrinking [17, 22].

ALS progressive rapidly after the disease onset, resulting in a death of the affected individual after 3-5 years of the start of the symptoms. On the other hand, MD gradually worsens and include more muscle groups being affected by the disease.

Genetically, ALS is considered as sporadic, while MD is highly genetic [23, 22].

In contrast, Muscular Dystrophy is a group of inherited diseases characterized by progressive weakness and loss of muscle mass. The genetic mutations interfere with the production of proteins needed to form healthy muscle [22].

In terms of diagnosis, a muscle biopsy or electromyography (EMG) is often used to distinguish between ALS and other conditions [24].

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Frederika Malichová

Frederika Malichová

Frederika is a postgraduate researcher at the University of Cambridge, where she investigates new biomarkers for Frontotemporal Dementia and other tauopathies. Her research has been published at prestigious conferences such as the Alzheimer’s Association International Conference 2023. She obtained her BSc in Biomedical Sciences from UCL, where she worked closely with the UK Dementia Research Institute.