myositis

definition

a rare group of chronic, autoimmune conditions characterized by immune-mediated inflammation and progressive weakness of the skeletal muscles ()(symmetrical)

has a lot of systemic manifestation as well

general symptoms related to muscle weakness is : difficulty rising from a chair or combing their hair

rapid progressive

high CK, LDH

female 40-50 , but DM can be common in children , but inclusion body myositis common in men 50

subtypes of myositis

1. Dermatomyositis (DM)

2. Polymyositis (PM)

3. Immune-Mediated Necrotizing Myopathy (IMNM)

4. Antisynthetase Syndrome

5. Inclusion Body Myositis (IBM)

what’s the difference between myopathy and neuropathy ?

neuropathy : asymmetrical, more distal, sensory abnormalities

what’s the difference between myopathy and myositis ?

myopathy : not rapid, family history , no lab sing of muscle destruction like CK, LDH.

pathogenesis of DM

complement med vasculopathy

attacking muscular wall of capillaries: attacks the tiny blood vessels leading to inflammation

ab: anti M2 ( helicase )

pathogenesis of PM

directed T cell muscle injury

attacking then fascicles

dermatomyositis

distinct skin rashes and progressive, proximal muscle weakness

adults aged 40–60 or children aged 5–15 (known as Juvenile Dermatomyositis) , female

1. skin:

Gottron’s Papules: Scaly, symmetric, reddish-purple bumps found directly over the bony prominent surfaces of the knuckles, elbows, or knees

Heliotrope Rash: A symmetric, purplish-violaceous discoloration affecting the upper eyelids, often accompanied by mild swelling (edema) around the eyes.

Shawl Sign and V-Sign: Conspicuous, sun-sensitive rashes spreading over the upper back and shoulders (shawl configuration) or forming a V-shape on the lower neck and upper chest.

Mechanic’s Hands: Rough, cracked, hyperkeratotic skin on the lateral and palmar surfaces of the fingers

2. muscles

myalgia

progressive , symmetrical, painless, proximal muscle weakness ( hip and shoulder) ( mostly extensors )

diff rising from chair

dropped head

diff lifting and placing things

diff climbing stairs

Trendelenburg sign : drop of pelvis when they lift the leg

3. lung : interstitial lung disease , acute alveolitis, chronic progressive fibrosing alveolitis, respiratory failure. p. function test : Restrictive ventilatory defect with decrease diffusion capacity

CT: ground glass opacities: infiltrations : active / reticular opacities : fibrosis : chronic

asymptomatic , cough , dyspnea at rest , R failure

4. esophageal diseases: nasal regurgitation, dysphagia

5. myocarditis

6. malignancy

7. arthralgia, morning stiffness, non deforming , symmetrical arthritis in hands, wrist, feet and ankles

inclusion body myositis

most common one

it progresses slowly,

often affects distal muscles (like fingers and wrists) as well as the quadriceps,

is more common in men 50

is resistant to immunosuppressants.

asymmetric

atrophy

early in long finger flexors

no griping

foot drop

necrotizing autoimmune myositis

severe, acute

rapid muscle weakness

high rate of muscle cell death (necrosis)

paraneoplastic or induced by statins

ab: anti SRP

malignancy associated myositis

female 50

recurrent

high ESR

diagnosis

clinical

lab : high CK ( 50 , 100 : rhabdomyolysis ) , AST, ALT, LDH

US ( hyper echoic ) , MRI ( hyper intense , heterogenous )

Electromyography

needle biopsy ( from biceps, deltoid, v.lateralis ):

• PM: CD4+ infiltration surrounding each muscle fiber

• DM: CD4+ flirtation surrounding the fasciles and vessels

serology :

• antiRo/SSA, anti U1RNP

• anti synthetase ab ( tRNA stnthetase )

• Anti Mi 2 ( antihelicase )

• Anti SRP

• Anti MDA5 : interstitial lung D

• Anti TIF 1 gamma : paraneoplastic

Antisynthetase Syndrome

A systemic form

myositis

interstitial lung disease (ILD),

Raynaud’s phenomenon,

arthritis,

thickened, cracked skin on the hands ("mechanic's hands").

ab: anti tRNA synthetase

steroid dependent

relapsing

worse prognosis

therapy

1st line : steroids ( oral prednisolone )

incase of relapse : methotrexate, azathioprine

in case of severe and ILD and GI : IV methylprednisolone

other options : cyclophosphamide, MFM, tacrolimus, Rituximab

thromboembolism prophylaxis for immobility

gastric and jejunal tube / percutaneous endoscopic gastrostomy for dysphagia

respiratory dysfunction : muscle training, positioning , antibiotic, ventilation