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Myopathies vs Duchenne/Becker for MRCP Part 1

TL;DR

For MRCP Part 1, distinguishing Neuro: Myopathies vs. Dystrophies (Duchenne/Becker) is a common exam theme. Myopathies are a broad category of primary muscle diseases, whereas Duchenne and Becker muscular dystrophies are specific X-linked genetic disorders caused by mutations in the dystrophin gene. Exam questions typically focus on age of onset, inheritance, CK elevation, and cardiac involvement. Understanding these patterns allows candidates to rapidly identify the correct diagnosis in clinical scenarios.


Why this matters for MRCP Part 1

Neuromuscular questions in MRCP often present a short clinical vignette with a few decisive clues. Candidates must quickly recognise patterns.

Typical exam cues include:

  • Age at onset

  • Family history

  • Pattern of muscle weakness

  • Creatine kinase elevation

  • Cardiac involvement

Recognising these patterns allows candidates to differentiate inflammatory myopathies, metabolic myopathies, and muscular dystrophies within seconds.


Understanding Myopathies

A myopathy is a disorder primarily affecting skeletal muscle fibres. Unlike neuropathies, the pathology lies within the muscle rather than the nerve.

Common categories include:

  • Inflammatory myopathies – polymyositis, dermatomyositis

  • Metabolic myopathies – mitochondrial disease, glycogen storage disorders

  • Drug-induced myopathies – particularly statins

  • Genetic myopathies – muscular dystrophies

Clinical features of myopathy

Patients typically present with:

  • Symmetrical proximal muscle weakness

  • Difficulty climbing stairs

  • Difficulty rising from a chair

  • Difficulty lifting objects overhead

  • Normal sensation

Reflexes may be normal or reduced, and CK levels are usually elevated.


Muscular Dystrophies: A Subgroup of Genetic Myopathies

Muscular dystrophies are inherited disorders characterised by progressive muscle degeneration due to defects in structural proteins.

The most clinically important dystrophinopathies are:

  • Duchenne muscular dystrophy

  • Becker muscular dystrophy

Both conditions arise from mutations in the dystrophin gene (DMD) located on the X chromosome.

Authoritative clinical descriptions are available from NHS guidance on muscular dystrophy:https://www.nhs.uk/conditions/muscular-dystrophy/


The Role of Dystrophin

Dystrophin is a structural protein that links the cytoskeleton of muscle cells to the extracellular matrix.

Without dystrophin:

  • Muscle fibres become fragile

  • Repeated contraction leads to damage

  • Progressive muscle degeneration occurs

In exam questions:

  • Duchenne: dystrophin absent

  • Becker: dystrophin reduced but present


Duchenne vs Becker Muscular Dystrophy

The following comparison summarises the most tested MRCP differences.

Feature

Duchenne Muscular Dystrophy

Becker Muscular Dystrophy

Genetics

X-linked recessive

X-linked recessive

Mutation type

Frameshift deletion

Non-frameshift mutation

Dystrophin

Absent

Reduced

Onset

Early childhood (2–5 years)

Adolescence or adulthood

Severity

Severe

Milder

CK level

Markedly elevated

Elevated

Ambulation

Lost by early teens

Often preserved into adulthood

Cardiac involvement

Common

Common but later

These distinctions frequently appear in MRCP Part 1 single-best-answer questions.


Classic Duchenne Muscular Dystrophy Features

Duchenne muscular dystrophy is the most common childhood muscular dystrophy.

Typical exam clues include:

  • Delayed walking

  • Frequent falls

  • Difficulty climbing stairs

  • Gowers’ sign

  • Calf pseudohypertrophy

Gowers’ sign occurs when the child uses their hands to push against their thighs in order to stand up.

According to Gene Reviews (NIH), CK levels in Duchenne are often 10–100 times the normal range.https://www.ncbi.nlm.nih.gov/books/NBK1119/

Without treatment, most patients lose the ability to walk by their early teens.


Becker Muscular Dystrophy

Becker muscular dystrophy is a milder dystrophinopathy.

Key features include:

  • Later onset (adolescence or early adulthood)

  • Slower progression

  • Residual dystrophin function

  • Longer life expectancy

Many patients remain ambulant into adulthood.

Interestingly, cardiomyopathy may be the first presentation, which is an important exam clue.

More details are summarised by MedlinePlus Genetics:https://medlineplus.gov/genetics/condition/becker-muscular-dystrophy/


Diagnostic Approach

MRCP questions often test laboratory interpretation.

Typical investigations include:

Creatine kinase

CK levels are markedly elevated due to muscle breakdown.

Genetic testing

Modern diagnosis is confirmed by identifying mutations in the DMD gene.

Muscle biopsy

Historically used but now less common. Findings include:

  • Muscle fibre degeneration

  • Absence or reduction of dystrophin on immunostaining

Cardiac evaluation

Patients require monitoring for:

  • Dilated cardiomyopathy

  • Arrhythmias


Mini Clinical Case (MRCP-style)

A 4-year-old boy is brought to clinic because of frequent falls. His parents report difficulty climbing stairs. On examination, he uses his hands to push himself upright from the floor. Calf muscles appear enlarged.

Blood tests show markedly elevated creatine kinase.

What is the most likely diagnosis?

A. Becker muscular dystrophyB. Duchenne muscular dystrophyC. PolymyositisD. Myasthenia gravisE. Motor neurone disease

Answer: B. Duchenne muscular dystrophy

Explanation

Early childhood onset, Gowers’ sign, calf pseudohypertrophy, and very high CK levels strongly indicate Duchenne muscular dystrophy. Becker muscular dystrophy typically presents later with milder symptoms.


Five Most Tested Subtopics in MRCP Part 1

Focus revision on these key exam themes:

  1. X-linked inheritance of dystrophinopathies

  2. Gowers’ sign and proximal muscle weakness

  3. CK elevation patterns

  4. Frameshift vs non-frameshift mutations

  5. Dilated cardiomyopathy in muscular dystrophy


Study Tip Checklist for Revision

Use the following checklist when revising neuromuscular conditions.

✔ Identify pattern of weakness (proximal vs distal)✔ Check age of onset✔ Consider inheritance pattern✔ Compare CK levels✔ Assess cardiac involvement

Practising clinical scenarios helps consolidate these patterns. You can attempt exam-style questions in the Free MRCP MCQs or simulate exam conditions using Start a mock test.

For structured teaching sessions, explore MRCP revision lectures.


MRCP Part 1 neurology revision with study notes on muscular dystrophy and neuromuscular disorders.

Common Pitfalls (Exam Traps)

  • Confusing Becker muscular dystrophy with Duchenne when onset age is not considered

  • Missing cardiac involvement in Becker disease

  • Misclassifying proximal weakness as neuropathy

  • Forgetting the X-linked inheritance pattern

  • Assuming all muscular dystrophies present in childhood


FAQs

What is the difference between Duchenne and Becker muscular dystrophy?

Duchenne muscular dystrophy results from a frameshift mutation causing absent dystrophin, leading to severe early-onset disease. Becker muscular dystrophy involves non-frameshift mutations, allowing partially functional dystrophin and a milder course.

Why is creatine kinase elevated in muscular dystrophy?

Creatine kinase leaks into the bloodstream when muscle fibres break down. In Duchenne muscular dystrophy, CK can rise to 10–100 times normal levels.

What is Gowers’ sign?

Gowers’ sign occurs when a child uses their hands to “climb up” their legs to stand. It reflects proximal muscle weakness and is strongly associated with Duchenne muscular dystrophy.

Can Becker muscular dystrophy present with heart disease first?

Yes. Some patients with Becker muscular dystrophy initially present with dilated cardiomyopathy before significant skeletal muscle weakness develops.

Are muscular dystrophies inherited?

Most muscular dystrophies are genetic disorders. Duchenne and Becker are X-linked recessive, meaning males are affected while females usually act as carriers.


Ready to start?

Success in MRCP Part 1 depends on recognising high-yield clinical patterns across multiple specialties. Strengthen your neurology revision by reviewing the MRCP Part 1 overview and practising questions with the Free MRCP MCQs.

You can also test your readiness using a timed MRCP mock test or attend structured teaching sessions through the MRCP revision lectures.


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