Poly myositis and dermatomyositis · Polymyositis: differential diagnosis Polymyositis and...

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Poly myositis and dermatomyositis

Are acquired . chronic , inflammatory muscle condition of

unknown cause

-Age : most cases are in 5th and 6th decades of life.

-Incidence:0.5 per 100,000 population


Polymyositis (PM) and dermatomyositis (DM)

-adult polymyositis

-adult dermatomyositis

-adult polymyositis, dermatomyositis with malignancies

-PM/DM in association with other connective tissue diseases

-childhood DM.

-inclusion body myositis


-Mascular weakness is the dominant feature of

myositis syndromes

-Symmetryical

-Proximal muscle of extremities,trunk and neck


-Lower extremities characterized by

.An inability to climb stairs

.To arise from low seat

.Walking may be limited and gait may become poorly coordinated

and waddling

-Upper extremities

.Limits lifting

.Handing up clothes and combing the hair

-Weakness of the anterior neck flexor muscles interferes with

lifting the head from the supine position and arising from bed

become difficult


Adult polymysitis (PM)

- Women: men 3:1

The onset can be insidious, over month’s, but can be acute


-Malaise- weight loss and fever can develop during the

acute phase

-The major feature of PM is proximal muscle weakness

which is progressive

-There is wasting of the shoulder and pelvic girdle

muscles with weakness

-Pain and tenderness are uncommon

-Patients have difficulty squatting going upstairs,

raising from a chair raising their hands above the

head and holding their head up.


-Involvement of pharyngeal, laryngeal and respiratory

muscles can lead to dysphagia , dysphonia and

respiratory failure.

-Interstitial lung fibrosis

-Arthrlgia 50%

-Raynaud’s phenomenon

-cardiac abnormalities (heart block

,myocarditis,congestive heart failure)


Adult dermatomyositis

-more in women

-heliotrope rash and perorbital oedema

-gottron rash

-ulcerative vascuilitis

-subcutaneous calcinosis 25%


Dermatomyositis: heliotrope rash


Dermatomyositis: diffuse facial erythema


Dermatomyositis: rash, chest


Dermatomyositis: edema and rash, hand


Dermatomyositis: erythematous lesions, hands


Dermatomyosistis: rash, hands


Dermatomyositis: “mechanic’s hands”


Dermatomyosistis: periungual involvement


Dermatomyositis: rash, knees


Dermatomyositis: subcutaneous calcification, knees


Dermatomyositis: calcinosis, thigh (radiograph)


Associated with malignancies

-The associated cancer may not become apparent for 2-3 years.

-Recurrent or refractory dermatomyositis should prompt a search

for occult malignancy

-Lung, ovary, breast, stomach cancer can predate the onset of

myositis particularly in males with dematomyositis


Childhood dermatomyositis

-Age : 4-10 years

-Subcutaneous calcification maybe widespread and

severe

-Recurrent abdominal pain due to vascuilitis


Inclusion Body Myositis

General Features

Most common acquired muscle disease over the age of 50

Prevalence of 5-10/million

Affects men > women at 2-3:1

Average time from symptom onset to diagnosis is ~ 6 years


Clinical Features of IBM

• Consider IBM when confronted with refractory

polymyositis patient

• Insidious onset of painless muscle weakness with slow

progression

• Tendency to distal (away from the trunk muscles) and

asymmetric muscle involvement (“foot drop”)

• Difficulty swallowing

• Characteristic pattern of muscle atrophy (forearm

flexors, muscles of hands, thigh)


Inclusion body myositis

Males affected more than females

Age of onset usually greater than 50

Slowly progressive

Distal and asymmetric muscle weakness

Myopathic and neuropathic changes on EMG

Mononuclear cell infiltrates and vacuoles containing amyloid on

muscle biopsy

Responds poorly to corticosteroids


Polymyositis: differential diagnosis

Polymyositis and dermatomyositis

Hypothyroidism

Drug-induced myopathies

Corticosteroids, colchicine, HMG-CoA reductase inhibitors, zidovudine,

hydroxychloroquine, alcohol

Infections

Viral, toxoplasmosis, trichinosis, bacterial pyomyositis

Connective tissue disorders

Lupus, scleroderma, MCTD

Systemic vasculitis

PAN, Wegener’s granulomatosis


Polymyositis: differential diagnosis, cont’d

Metabolic myopathies

Disorders of carbohydrate and lipid metabolism

Electrolyte disturbances

Hypernatremia, hyponatremia, hypokalemia, hypophosphatemia,

hypocalcemia

Inclusion body myositis

Sarcoid myopathy

Amyloid myopathy

Neurologic disorders

Myasthenia gravis, motor neuron disease, muscular dystrophy


Neurological disease

-Asymmetrical weakness

-distal extremety inovlvement

-altered sesorium or abnormal cranialnerve function

-myopathies cause proximal and symmetrical weakness except

(IBM, Mitochondrial myopathies, antiSRP antibody)


-Limb-girdle dystrophy

positive family history

upper and lower extremity proximal muscle weakness may begin

in the first through third decades of life.

muscle wasting

-Duchenn`es musclar dystrophy

The age of 5 years

Muscle weakness and wasting

Hyperlordotic gait

Psuedo hypertrophy of the calf muscle


-Becker`s muscular dystrophy

Similar but milder

Patient able to walk beyond the age 16

-Facioscapulo humeral

Autosomal dominant

Weakness begin in the facial muscle


Don’t Forget

Patients with hypothyroidism can

present with diffuse and nonspecific

arthralgias and myalgias. CKs may be

elevated


Think About Toxic Drug Reactions That Can Cause

Musculoskeletal Pain

Hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase

inhibitor

Zidovudine (AZT)

Ethanol

Clofibrate

Cyclosporin A

Penicillamine


Soft-Tissue Pain Syndromes:

Fibromyalgia

Widespread musculoskeletal pain

Decreased pain threshold and tolerance

May have tenderness in specific regions

(tender points)

Associated fatigue, sleep, somatic complaints

No objective inflammation seen on physical

examination

Normal laboratory findings


Common Causes of Proximal Muscle Weakness With

Elevated CK

Inflammatory myositis

Noninflammatory myopathies

Hypothyroidism

Hypokalemia

Alcoholism

Drugs

AZT

HMG-CoA reductase inhibitors

(the “statins”)


Myositis-specific antibodies

ANTIBODY DISEASE ASSOCIATION PREVALENCE

Anti-tRNA synthetases

(Jo-1)

Dermatomyositis,

interstitial lung disease,

“mechanic’s hands”

20%

Anti-SRP (signal

recognition protein)

African-American women,

poor prognosis

Rare

Anti-Mi-2

Older women, “shawl

sign,” good prognosis

5%

PM/SCL

Polymyositis/scleroderma

overlap

Rare


-EMG

-Needle muscle biopsy

-MRI

-screening for malignancy


Proposed diagnostic criteria for polymyositis and

dermatomyositis

PM diagnosed as definite with 4 out of 5 of the below criteria or probable

with 3 out of 5

DM diagnosed as definite with rash plus 3 out of 4 of the below criteria or

probable with rash plus 2 out of 4 criteria

Symmetric proximal muscle weakness

Elevated muscle enzymes (CPK, aldolase, transaminases, LDH)

Myopathic EMG abnormalities

Typical changes on muscle biopsy

Typical rash of dermatomyositis


Polymyositis/Dermatomyositis

-Therapy

Prednisone 1–2 mg/kg, as initial therapy

Methotrexate or azathioprine is often added

Intravenous immunoglobulin in rapidly progressive or refractory

cases


Treatment Options in Myositis

Corticosteroids (prednisone)

Immunosuppressive agents

Methotrexate cyclosporine

Azathioprine cyclophosphamide

leflunomide chlorambucil

mycophenolate mofetil

IVIg

Anti-TNF agents (etanercept, infliximab)

“Biologic” response modifiers

rituximab

Oxandrolone (IBM)

Other (stem cell transplant)

Poly myositis and dermatomyositis · Polymyositis: differential diagnosis Polymyositis and...

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