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Rheumatology > Myositis - polymyositis + dermatomyositis > Flashcards

Myositis - polymyositis + dermatomyositis Flashcards

1
Q

What is myositis?

A

CTDs characterised by inflammation of muscles

Includes polymyositis and dermatomyositis (most common types)

Other types = necrotising autoimmune myopathy and sporadic inclusion body myositis (IBM)

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2
Q

TRUE OR FALSE
Dermatomyositis mainly affects the skin

A

FALSE

It can affect other body parts e.g., joints, oesophagus, lungs and heart

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3
Q

Which viral infections have been implicated in poly- + dermatomyositis?

A

HIV

Human T-cell lymphotropic virus type I (HTLV-I)

Simian retroviruses

Cocksackievirus B

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4
Q

What is the incidence of dermatomyositis?

A

1.4 cases per 100,000

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5
Q

What is the prevalence of dermatomyositis?

A

5.8 cases per 100,000

Higher prevalence amongst older age group

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6
Q

TRUE OR FALSE

Women are more likely to be affected by dermatomyositis than men

A

TRUE

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7
Q

What is the incidence of polymyositis?

A

3.8 cases per 100,000

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8
Q

What is the prevalence of polymyositis?

A

9.7 cases per 100,000

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9
Q

Is the onset of polymyositis slow or fast?

A

Gradual

Onset over weeks or months

Steady progression

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10
Q

In which muscle groups does muscle weakness develop?

A

Proximal muscles

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11
Q

Which actions does proximal myopathy make more difficult?

A

Rising from a chair

Climbing stairs

Lifting objects

Combing hair

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12
Q

Apart from diffuse weakness, what other symptoms may be present in polymyositis?

A

Fatigue

Myalgia

Muscle cramps

Dysphagia - caused by pharyngeal weakness

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13
Q

Which muscle groups are spared in polymyositis? Hence what are patients still able to do?

A

Distal muscles spared

Patients can still do fine motor movements of hand e.g., :
- buttoning a shirt
- writing
- operating a keyboard
- playing the piano

Affected only late in the disease

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14
Q

Is the weakness in polymyositis always at a constant level?

A

No

May vary from week to week or month to month

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15
Q

What proportion of patients with polymyositis have pain?

A

1/3

Hence not usually painful in most patients

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16
Q

Is there a skin rash in polymyositis?

A

No

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17
Q

What would there be no FHx of in polymyositis?

A

Neuromuscular disease

Also no evidence of endocrine disorder or Hx of exposure to possible toxins

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18
Q

What may you see on examination of a patient with polymyositis?

A

Proximal muscle weakness, sparing of distal muscles until disease is well advanced

External ocular muscles unaffected

Facial muscles affected only in severe disease

Weak forced flexion of neck - there could be difficulty holding the neck up

Muscular atrophy with preservation of tendon reflexes, flexor plantar response and normal sensation

Muscles may be tender on palpation with a nodular grainy feel

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19
Q

What investigations would you do for polymyositis and what would you expect to find?

A

Creatine kinase - up to 50 times normal (rarely normal in active disease - good indication of disease activity)

Anti-Jo-1 antibodies - in 20%

Other enzymes = aldolase, serum glutamic-oxaloacetic transaminase (SOGT), serum glutamic-pyruvic transaminase (SGPT) and LDH

EMG + confirmed by muscle biopsy - definitive test for polymyositis

CA 125, CA 19-9 - useful markers for malignancy

Myositis-specific antibody (MSA) and myositis-associated autoantibodies (MMA) - useful for differentiating patients with underlying malignancy

20
Q

If a patient with polymyositis have anti-Jo-1 antibodies, is this a good or bad prognosis?

A

Poor prognosis, with interstitial lung disease which occurs in about 1/3

21
Q

In polymyositis if SGOT is higher than SGPT what type of cause should be suspected?

A

Myogenic cause

22
Q

What are the other DDx for polymyositis?

A

Hereditary neuromuscular diseases

Endocrine disease inc. thyrotoxicosis and Cushing’s disease

Malabsorption syndromes e.g., alcoholism, cancer, vasculitis, granulomatous disease, sarcoidosis or exposure to drugs or toxins that affect the muscles

23
Q

TRUE OR FALSE
Dermatomyositis affects both children and adults

A

TRUE

24
Q

What pattern of muscle weakness does dermatomyositis have?

A

Same as polymyositis

25
Q

Which condition can dermatomyositis resemble?

A

Scleroderma with Raynaud’s phenomenon and dysphagia

As it also has systemic upset with fever, arthralgia, malaise and weight loss

26
Q

What possible cardiac diseases can occur in dermatomyositis?

A

AV conduction defections

Tachyarrhythmias

Dilated cardiomyopathy

27
Q

What possible GI diseases can occur in dermatomyositis?

A

GI ulcers and infections

28
Q

What possible lung diseases can occur in dermatomyositis?

A

Interstitial lung diseases in 30-50%

Thoracic muscles may be weak

29
Q

Which features of dermatomyositis do children tend to have more?

A

Non-muscular features esp GI ulcers and infections

30
Q

What % of new diagnosis of dermatomyositis have an underlying malignancy?

A

25%

More strongly associated with malignancy than polymyositis

31
Q

What are the signs/symptoms on the face of dermatomyositis?

A

Heliotrope rash
- bilateral peri-orbital violaceous colouration with associated swelling

32
Q

What are the signs/symptoms in the eyes of dermatomyositis?

A

Retinopathy
- haemorrhages & cotton-wool spots

33
Q

What are the signs/symptoms on the hands of dermatomyositis?

A

Gottron’s papules
- roughened erythematous regions on the hands, elbows and knees

Loss of cuticles

Subcutaneous calcinosis

Nailfold redness

Raynaud’s sign

Mechanics hands
- hyperkeratotic changes leading to painful rough skin cracking of the fingertips

Photosensitivity

34
Q

What are the signs/symptoms in the thorax of dermatomyositis?

A

Shawl sign
- fixed erythema on photosensitive areas of the back, shoulders, chest and neck

35
Q

Name other e signs/symptoms eyes of dermatomyositis

A

Bibasal pulmonary fibrosis

Pyrexia

Myocarditis, arrythmias

Arthritis

36
Q

What bedside Ix would you do for dermatomyositis?

A

EMG - abnormal spontaneous and voluntary activity

37
Q

What bloods would you do for dermatomyositis?

A

LDH = elevated

LFTs (ALT, AST) = elevated

Creatine kinase = elevated (in the 1,000s)

Serum aldolase = elevated

38
Q

What imaging would you do for dermatomyositis?

A

High-resolution CT - shows pulmonary fibrosis in anti-synthase syndrome

39
Q

What special Ix would you do for dermatomyositis?

A

Biopsy of skin and muscle = definitive Ix

Malignancy screening = tumour markers, CXR, mammogram, USS, CT

40
Q

What antibodies Ix would you do for dermatomyositis?

A

ANA = 80% sensitive

Anti-Jo-1 = anti-synthase syndrome

Anti-SRP = polymyositis&raquo_space;> dermatomyositis

Anti-M2 = dermatomyositis (25%) > polymyositis

41
Q

What are the DDx for dermatomyositis?

A

SLE in which the skin over the phalanges is involved and the skin of the MCP join is spared - reverse is true in dermatomyositis

Systemic sclerosis

Rheumatoid arthritis

Sjogren’s syndrome

42
Q

Which other autoimmune diseases can poly- and dermatomyositis be associated with?

A

Myasthenia gravis

Hashimoto’s thyroiditis

Systemic sclerosis

Waldenstrom’s macroglobulinaemia

43
Q

Which cancers are particularly increased in dermatomyositis?

A

Ovarian

Lung

Breast

Pancreatic

44
Q

Which cancers are particularly increased in polymyositis?

A

Lymphatic and haematopoietic malignancies e.g., :
- non-Hodgkin’s disease

45
Q

Sources

A

https://patient.info/doctor/myositis-polymyositis-and-dermatomyositis

https://zerotofinals.com/medicine/rheumatology/myositis/

Rheumatology (6 decks)

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