Polymyositis and Dermatomyositis

Question 1

What is polymyositis?

Answer 1

An idiopathic inflammatory myopathy causing symmetrical, proximal muscle weakness

Question 2

How does dermatomyositis differ from polymyositis?

Answer 2

Dermatomyositis includes cutaneous manifestations in addition to muscle weakness

Question 3

What is the common age and gender affected by polymyositis/dermatomyositis?

Answer 3

Females (2:1 ratio)

Peak incidence ages 40-50

Question 4

What is the key autoimmune mechanism in polymyositis?

Answer 4

T cell-mediated attack on muscle antigens, involving CD8+ T cells and macrophages

Question 5

What are the main clinical features of polymyositis?

Answer 5

(1) Symmetrical
(2) proximal muscle weakness with gradual onset

Question 6

What is Gottron’s sign?

Answer 6

A rash over the knuckles

= characteristic of dermatomyositis

Question 7

Name an antibody associated with interstitial lung disease in myositis patients

Answer 7

Anti-Jo-1 antibody

Question 8

First-line investigation for polymyositis and dermatomyositis?

Answer 8

Blood test for creatine kinase (CK)
= typically elevated

Question 9

What is the gold standard diagnostic test for polymyositis/dermatomyositis and why?

Answer 9

Muscle biopsy

= shows perivascular inflammation and necrosis

Question 10

What is the primary treatment for polymyositis/dermatomyositis?

Answer 10

Prednisolone (first-line)

with the possible addition of methotrexate or rituximab if unresponsive

Question 11

What are common cutaneous signs in dermatomyositis?

Answer 11

Gottron’s papules
Heliotrope rash
Shawl sign

Question 12

What are the first and second-line treatments for polymyositis and dermatomyositis?

Answer 12

First-line
= Prednisolone +/- methotrexate

Second-line
= Rituximab or other immunosuppressive therapies

Question 13

Name a syndrome associated with myositis and its key features

Answer 13

Anti-synthetase syndrome

= includes
(1) mechanic’s hands
(2) raynaud’s phenomenon
(3) myositis
(4) interstitial lung disease
(5) polyarthritis

Question 14

What symptom may suggest early dermatomyositis involvement?

Answer 14

Difficulty with activities like brushing hair or climbing stairs due to proximal muscle weakness

Question 15

What physical tests assess muscle strength in myositis?

Answer 15

(1) Confrontational testing
(direct power)

(2) Isotonic testing
(eg, 30-second sit-to-stand)

Question 16

What is the “shawl sign” in dermatomyositis?

Answer 16

A reddish-purple rash over the shoulders and upper back

Question 17

Which muscle enzyme is a key indicator of disease activity in polymyositis and dermatomyositis?

Answer 17

Creatine kinase (CK)

Question 18

How can dermatomyositis be present on the hands?

Answer 18

Gottron’s papules (scaly, erythematous knuckle lesions)

Question 19

Name two myositis-specific autoantibodies.

Answer 19

Anti-Jo-1 and anti-SRP

Question 20

What is the significance of a high creatine kinase (CK) level in myositis?

Answer 20

Diagnostic for muscle inflammation, often 10x the normal limit

Question 21

Which antibodies are characteristically associated with dermatomyositis?

Answer 21

Anti Mi-2 and ANA (more common)

Question 22

What is the antibody associated with the extra-muscular features of dermatomyositis?

Answer 22

anti-Jo1

Question 23

Which antibodies are characteristically associated with polymyositis?

Answer 23

anti-Jo1

Question 24

What are the features of polymyositis?

Answer 24

Diffuse proximal muscle weakness.

Question 25

Second-line investigation for polymyositis and dermatomyositis?

Answer 25

Autoantibodies: = Myositis specific - Anti-Jo-1, anti-SRP = Non-specific - ANA, anti-RNP

Question 26

2nd line test after muscle biopsy

Answer 26

MRI

Question 27

Dermatomyositis causes the same muscular symptoms as in polymyositis, but also causes characteristic rashes to develop, most notably what?

Answer 27

1. Gottron's papules 2. Heliotrope rash

Question 28

A 43-year-old female presents with a 3-week history of worsening weakness in her upper arms and legs. As a result, she struggles to stand up from a chair and brush her hair. However, she still has good fine motor skills in her hands. Examination reveals bilateral proximal (hip and shoulder girdle) muscle weakness. She denies skin changes but does report some muscle aches over the same period. Given the likely diagnosis, what test is unlikely to be significantly raised?

Answer 28

Alkaline phosphatase (ALP)

Question 29

A 57-year-old woman presents with fatigue and worsening shoulder weakness. She has noticed a slight change in her voice over time and feels it is hoarser. She reports muscle and joint aches and an occasional fever. Due to breathlessness, she has taken sick leave and can no longer complete her daily runs. She has been taking vitamin D supplements, suspecting deficiency as the cause of her symptoms. On examination, she has roughened skin on her knuckles and elbows, a red rash on her eyes, and puffiness. Blood tests show elevated lactate dehydrogenase, AST, ALT, and creatine kinase. EMG and muscle biopsy confirm the diagnosis. Given the likely diagnosis, what is the most important complication to be screened for?

Answer 29

Underlying malignancy

Question 30

A 50-year-old woman presents to the GP feeling weak. She describes difficulty getting up when sitting on a chair and struggles with steps and lifting objects. She hasn't had any pain, fever, or weight loss. Her medical history is insignificant; the only medication she takes is a multivitamin. On examination, you note power 4/5 in proximal muscle groups. She has no skin changes. Given the most likely diagnosis, which test would you order for first line?

Answer 30

Creatine kinase (CK)

Question 31

Which investigation would reveal the diagnosis for those with polymyositis and dermatomyositis?

Answer 31

Muscle biopsy

Question 31

A 50-year-old man presents with gradually worsening symmetrical muscle weakness, predominantly in the proximal limbs, and a recent increase in creatine kinase levels. Given the most likely diagnosis, what clinical features is most likely to also be present?

Answer 31

Interstitial lung disease

Question 32

What are the cutaneous features of dermatomyositis?

Answer 32

(1) Gottron’s papules = red papules on the dorsal aspect of the finger joints (2) Shawl rash = erythema across the upper back and shoulders (3) Nailfold erythema (4) Heliotrope rash = a purple rash on the eyelids (5) bilateral proximal muscle weakness

Question 32

What are the lesions found on the finger joints of an individual with dermatomyositis known as?

Answer 32

Gottron's papules

Question 33

Which myopathy is associated with underlying malignancy?

Answer 33

Dermatomyositis

Question 34

What is the rash found on the eyes of people with dermatomyositis known as?

Answer 34

Heliotrope rash

Question 35

Anti-Mi-2 antibodies are specific for what disease?

Answer 35

Dermatomyositis

Question 36

A 55-year-old woman has progressive weakness and fatigue. She can no longer stand for a long time and has difficulty getting up out of a chair. On examination, her hands are extremely dry and cracked, and there are rough erythematous papules and plaques over the extensor surfaces of the fingers There is reduced power in her hips and shoulders. She has a past medical history of anxiety and admits to regularly washing her hands out of fear of 'spreading germs' in light of the COVID-19 pandemic and she has smoked 40 cigarettes a day for the last 35 years. What is the next best step in her management?

Answer 36

Urgent referral to rheumatology as the Patient is presenting with Gottron's papules = roughened red papules over the knuckles

Question 37

How to investigate for malignancy?

Answer 37

CT scan

Question 38

A 54-year-old woman complains of pain and weakness in her muscles, especially when going upstairs. She also has a rash on the back of her hands and purple discolouration around the eyes. Examination reveals pain on muscle palpation and 4/5 power of her quadriceps and biceps muscles What investigation finding is most specific for the underlying diagnosis?

Answer 38

Anti-Mi-2 antibodies as specific for dermatomyositis ANA is mainly positive not specific

Question 39

How can polymyositis lead to type 2 respiratory failure?

Answer 39

Respiratory muscle weakness in polymyositis can impair ventilation = leading to hypoventilation, which causes low oxygen levels and high carbon dioxide levels

Question 40

A 65-year-old farmer presents with rough red papules over his knuckles. This has developed over a number of weeks and he cannot identify a specific cause. He describes the rash as itchy and painful. Recently, he has had difficulty in work with heavy lifting and climbing up steps. Which condition best explains this patient's symptoms?

Answer 40

Gottron's papules, roughened red papules over the knuckles mainly, are seen in dermatomyositis