PACES PATHFINDERS LEARNING LIBRARY

Approach to Progressive Proximal Muscle Weakness

Dermatomyositis • Polymyositis • Inflammatory Myopathies • MRCP (UK) PACES

A structured MRCP (UK) PACES approach to patients presenting with progressive proximal muscle weakness. Learn to recognise inflammatory myopathies, identify the characteristic skin manifestations of dermatomyositis and investigate associated systemic disease and malignancy.

12 min read Presenting Complaint Extremely High Yield

At a Glance

Presentation Progressive Proximal Muscle Weakness
Must Not Miss Dermatomyositis
Important Alternative Polymyositis
Key Clinical Clue Characteristic Skin Rash
Important Association Underlying Malignancy
Clinical Priority Assess Muscle Power & Swallowing

Red Flags

Rapidly progressive weakness Frequent falls Dysphagia Weight loss Heliotrope rash Gottron papules Breathlessness (ILD) Possible malignancy

PACES Approach

① Confirm true proximal weakness ② Look for skin manifestations ③ Screen for systemic involvement ④ Exclude mimics ⑤ Search for associated malignancy

Proximal Muscle Weakness Framework

Difficulty Rising
Chair test
Difficulty Climbing Stairs
Hip girdle weakness
Difficulty Combing Hair
Shoulder girdle weakness
Heliotrope Rash
Dermatomyositis
Gottron Papules
Pathognomonic clue
Weight Loss
Think malignancy

Overview

Progressive proximal muscle weakness is a classic MRCP (UK) PACES presentation. Dermatomyositis should be suspected when symmetrical proximal muscle weakness is accompanied by characteristic cutaneous manifestations such as heliotrope rash, Gottron papules, mechanic's hands, V-sign or shawl sign. Because adult-onset dermatomyositis may be associated with an underlying malignancy, every patient requires a systematic assessment for occult cancer in addition to evaluation of muscle, skin, pulmonary and oesophageal involvement. :contentReference[oaicite:1]{index=1}

Structured History

Characterising the Weakness

Skin Symptoms

Systemic Features

Screen for Organ Involvement

Screen for Associated Malignancy

Drug & Past History

Examination

Differential Diagnosis

Dermatomyositis Polymyositis Inclusion Body Myositis Steroid Myopathy Statin Myopathy Hypothyroid Myopathy Myasthenia Gravis Motor Neurone Disease Muscular Dystrophy Osteomalacia

Investigations

Baseline Blood Tests

Autoimmune Profile

Specialised Investigations

Assessment for Systemic Disease

Malignancy Screening

Diagnosis

Progressive Proximal Muscle Weakness due to Dermatomyositis

Dermatomyositis is an idiopathic inflammatory myopathy characterised by symmetrical proximal muscle weakness and distinctive cutaneous manifestations, including heliotrope rash and Gottron papules. Adults require careful assessment for associated malignancy, while systemic involvement may include dysphagia, interstitial lung disease and myocarditis. :contentReference[oaicite:1]{index=1}

Management

Control Inflammation High-dose corticosteroids are first-line therapy. Steroid-sparing immunosuppressive agents such as methotrexate, azathioprine or mycophenolate mofetil are commonly introduced for long-term disease control.
Treat Systemic Disease Manage dysphagia, interstitial lung disease, cardiac involvement and skin disease with a multidisciplinary team including rheumatology, dermatology, respiratory medicine and physiotherapy.
Search for Malignancy Adults should undergo appropriate malignancy screening based on age, symptoms and risk factors, as dermatomyositis may be a paraneoplastic condition.

Explaining to the Patient

"Your symptoms suggest inflammation affecting both your muscles and your skin. This explains the weakness, difficulty climbing stairs and the characteristic rash. We will arrange blood tests, muscle investigations and imaging to confirm the diagnosis, and we will also perform appropriate screening for any associated conditions, including certain cancers, because early detection is important. Treatment aims to reduce the inflammation, improve muscle strength and prevent long-term complications."

Examiner's Corner

How do you differentiate Dermatomyositis from Polymyositis?
  • Dermatomyositis: Symmetrical proximal muscle weakness accompanied by characteristic skin manifestations such as heliotrope rash, Gottron papules, V-sign, Shawl sign and mechanic's hands.
  • Polymyositis: Symmetrical proximal muscle weakness without the characteristic cutaneous features.
  • Both conditions may present with dysphagia, interstitial lung disease and elevated muscle enzymes.
What is Antisynthetase Syndrome?
  • Autoimmune inflammatory myopathy associated with anti-Jo-1 antibodies.
  • Characterised by inflammatory myopathy, interstitial lung disease, arthritis, Raynaud's phenomenon and mechanic's hands.
  • Pulmonary involvement is a major determinant of prognosis.
Why is malignancy screening important?
  • Adult-onset dermatomyositis has a recognised association with underlying malignancy.
  • The highest risk is during the first few years after diagnosis.
  • Common associated cancers include ovarian, lung, breast, colorectal, pancreatic and gastric malignancies.
  • All adult patients should undergo age-appropriate malignancy screening and further investigation when clinically indicated.
How do you differentiate Dermatomyositis from Inclusion Body Myositis?
  • Dermatomyositis: Symmetrical proximal weakness with characteristic skin rash.
  • Inclusion Body Myositis: Older age, slowly progressive weakness, involvement of finger flexors and quadriceps, often asymmetrical, poor response to immunosuppression.
Common Viva Questions
  • What are the causes of proximal muscle weakness?
  • What are the characteristic skin signs of dermatomyositis?
  • Which antibody is associated with antisynthetase syndrome?
  • Why does dysphagia occur?
  • Which investigation confirms inflammatory myopathy?
  • When should muscle biopsy be performed?
  • How would you screen for malignancy?
Important Clinical Pearls
  • Always examine the eyelids, knuckles, nailfolds and hands before testing muscle power.
  • Progressive symmetrical proximal weakness strongly suggests inflammatory myopathy.
  • Interstitial lung disease may be the presenting feature.
  • Creatine kinase is usually markedly elevated but may be normal in selected patients.
  • Muscle biopsy remains the diagnostic gold standard when uncertainty persists.

Pathfinder Pearls

Difficulty climbing stairs = proximal weakness Difficulty combing hair = shoulder girdle weakness Heliotrope rash is highly characteristic Gottron papules are pathognomonic Always ask about dysphagia Listen for ILD with bibasal crackles Screen every adult for malignancy Think antisynthetase syndrome with ILD + mechanic's hands

Common Pitfalls

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