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Idiopathic Inflammatory Myopathies (IIM)
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• Chronic inflammation of striated muscle (myositis)
• Characteristic cutaneous features
• Variety of systemic complications
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●The characteristic “heliotrope” rash of dermatomyositis was first described in 1875 (Paris).● Eleven years later Wagner coined the term polymyositis (PM) ●Gottron, in 1930, reported on the skin lesions of dermatomyositis .●1975, Bohan and Peter proposed five criteria or the diagnosis of PM and DM that are still used today
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Epidemiology Prevalence of DM and PM ~ 1/100,000
• The overall incidence of IIM ranges from 2 to 10 new cases per million persons at risk per year
• The prevalence of IBM in Western Australia is
high
Prevalence of IBM: 5-10/million (in> 50 y/o: 1-3/100,000)
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• IIM can occur at any age, includes both childhood and adult peaks.
• The mean age of myositis onset is increased when there is an associated malignancy.
• The overall female-to-male incidence ratio is 2.5:1.
• This ratio is lower(nearly 1:1) in childhood disease and with malignancy.
• (10:1)when there is a coexisting connective tissue disease.
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Association with other disorders
• PM-DM occurs in overlap with SSc more than any other CTD.
• Often associated with one of several serum autoantibodes such as anti-U1-RNP, anti-PM-Scl, or anti-U3-RNP.
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Environmental factors
• Disease onset is more frequent in the winter and spring months, especially in childhood cases
• Disease relapses were noted most frequently
during summer months, perhaps precipitated by infection or sun exposure.
• DM and PM have occurred in HIV-infected patients
• Myositis occurs in GVHD.
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Genetic and Environmental Risk Factors
Genetic
• Reports of familial occurrence
• Higher incidence of other autoimmune disorders in first degree relatives
• HLA DRB1
• DR3 in Anti Jo-1 Ab
Environmental Risk Factors
• Infectious Agents• Drugs• Ultraviolet radiation exposure• Other agents
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Genetic factors• (HLA-DRB1*03-DQA1*05-DQB1*02), are
important risk factors (anti-synthetase, antibody-positive patients)
• JDM associated with HLA-DQA1*0501.• Single nucleotide polymorphism have
identified associations in genes outside the MHC area.
• Genes regulating cytokines and their receptors including PTPN22, interleukin (IL)-1,and tumor necrosis factor (TNF)-a appear to play a role in the development and course of both childhood and adult onset myositis.
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Idiopathic Inflammatory Myopathies
• Polymyositis (PM)
• Dermatomyositis (DM)
• Inclusion body myositis (IBM)
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Clinical manifestations
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ماه6-3شروع تدریجی درعرض گرفتاری شدید کمربند شانه ایی ولگنی
درصد مواقع50گرفتاری گردن در عدم گرفتاری چشم وصورت
گرفتاری عضالت دیستال ناشایع استدیسفاژی ودیستونی داریم
در بچه ها و بالغان جوان شروع ممکن است سریعتر و با درد عضالنی همراه باشد
آتروفی در موارد شدید و طول کشیدهگرفتری دیافراگم می تواند باعث نارسایی
تنفسی شود
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• Other early findings included pitting edema of the extremities or eyelids as a combined result of hypoalbuminemia
• Capillary leakage, and lack of muscle tone needed to promote central venous return.
• Pharyngeal muscle weakness may contribute to hoarseness, dysphagia, nasal regurgitation of liquids, or aspiration pneumonia.
• Ventilatory muscle weakness may contribute to dyspnea
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• Unlike muscle weakness, which is a hallmark of PM-DM, muscle hypertrophy is more characteristic of muscular dystrophy.
• Muscle atrophy and joint
contractures are sequelae of disease damage; they are therefore late findings
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Constitutional• Fatigue is a prominent complaint and it
may persist even after adequate treatment of myositis.
• Fever is more commonly observed with JDM, and anti-synthetase syndrome.
• Weight loss may occur in myositis patients, but if persistent and severe, associated malignancy should be considered.
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Skin findings in DM
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• Gottron papules are scaly, erythematous or violaceous papules, and plaques located over bony prominences, particularly the MTP and proximal and DIP joints of the hands.
• Gottron sign is a macular erythema that occursn in the same distribution. One of these rashes is seen in 60% to 80%of patients with DM.
• Pruritus is common,particularly in the scalp and its presence differentiates DM from SLE, in which pruritus is uncommon.
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Gottron's sign
symmetric, roughened, erythematous skin changes over extensor surfaces of MCPs, IPs, elbows, and/or knees
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• Heliotrope rash is purplish in color, may be edematous or scaling in nature, and is located in the periorbital area, especially over the upper eyelids
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Heliotrope rash
a violaceous eruption on the upper eyelids, sometimes with edema
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Shawl sign, V signa diffuse flat erythema in a shawl-like distribution or in a V-shaped pattern over the anterior neck and chest
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Erythroderma
a generalized redness (at a variety of other skin sites: malar, forehead)
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Periungual abnormalities
erythematous capillary nailbeds with vascular changes (like other CTDs) Abnormal loops with areas of dilatation and dropout
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Calcinosis• Soft tissue calcification, which can be
disabling, occurs most commonly in chronic, childhood-onset DM and is less frequent in adult-onset disease.
• Calcinosis may appear in well-controlled myositis but more typically occurs in the setting of chronic, active disease or aftera prolonged delay in the initiation of corticosteroid treatment.
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• Calcinosis may be intracutaneous, subcutaneous, fascial, or intramuscular in location, with a predilection for sites of repeated microtrauma (elbows, knees, flexor surfaces of fingers, and buttocks).
• Medical therapy has been disappointing; however,bisphosphonates have led to rapid improvement in some cases,whereas probenecid and infliximab have been beneficial in othersituations.
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بالینی تظاهراتریه
• ILD important complication in approximately %10 of cases of DM and PM
• Respiratory failure may result from diaphragmatic and chest wall muscle weakness
• ILD in the inflammatory myopathies often occurs in the context of anti-synthetase antibodies and the anti-synthetase syndrome
• Amyopathic patients remain at risk for fatal ILD, malignancy,or even delayed-onset, full-blown DM.
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Antisynthetase (anti-Jo-1) syndrome
• ILD
• Raynaud
• Arthritis
• mechanic's hands
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• Pulmonary function testing (PFT) reveals restrictive physiology inmyositis-associated ILD.
• NSIP and the organizing pneumonias represent more favorable histopathology, usual interstitial pneumonitis (UIP) and diffuse alveolar damage (DAD) portend a more ominous course.
• the concomitant finding of anti-Ro/SSA in patients with anti-synthetase autoantibodies may be associated with more severe and progressive ILD.
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• Diffuse alveolar hemorrhage with pulmonary capillaritis is uncommon but can be lethal.
• Pneumomediastinum, on the other hand, is increasingly reported.
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بالینی تظاهراتمری
• Dysphagia: Weakness of the striated muscle of the upper one-third of the esophagus (and/or the oropharyngeal muscles)
• more common in elderly patients and may underlie the increased incidence of bacterial pneumonia
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بالینی تظاهراتقلب
• Heart failure is unusual ↑ CK-MB fraction due to involvement of the
myocardium by the myositis
Reason for ↑CK-MB levels is that the fraction of MB is increased in regenerating muscle
Cardiac troponin I, a more specific and
sensitive marker of cardiac damage
Conduction and ECG abnormality
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Joints
• Polyarthralgias or polyarthritis, if they occur, appear early in the disease course.
• The distribution is rheumatoid-like, and the symptoms are relatively mild.
• Joint findings are more common with overlap and the anti-synthetase syndromes but are frequently in childhood Dm.
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IBM• سال50گرفتاری باالی • شروع تدریجی وسیرکند• سال قبل از تشخیص6-5بروزعالیم • میتواند غیرقرینه ” دیستال ویا فوکال
باشد• میتواند تغییرات نوروپاتیک داشته باشد• می تواند باعث آتروفی عضله کوادری
سپس شود
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Immunopathogenesis
Histologic features:
• muscle fiber necrosis
• degeneration and regeneration
• inflammatory cell infiltration
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Muscle Anatomy
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Normal Muscle
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DM
Cellular infiltrate is predominantly perifascicular and often perivascular
B cells and plasmacytoid dendritic cells
perivascular and perimysial inflammation
perifascicular necrosis in DM
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PMcellular infiltrate is found predominantly within the fascicle
cytotoxic CD8+ T cells are dominant
intense interstitial mononuclear infiltrate
with some myocyte degeneration
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IBMfilamentous inclusions in electron microscopy
Rimmed vacuoles and eosinophilic muscle
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An autoimmune disease
Association with other autoimmune diseases (: Hashimoto's thyroiditis) and collagen vascular diseases (: scleroderma)
Autoantibody response in many patients
Lymphocyte infiltration:
• B cells and plasmacytoid dendritic cells in DM• cytotoxic CD8+ T cells
response to immunosuppressive therapies in some patients
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Dermatomyositis
Humoral immune process against vascular endothelium
activation of complement↓
C5b-9 deposition on endothelium↓
capillary necrosis ↓
ischemic muscle injuryperifascicular atrophy
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PM and IBM
MHC-1 expression on myocytes
Activation of CD8 T cells and lysis of muscle fibers by release of Perforin granules
Upregulation of cytokines, chemokines and adhesion molecules → ↑transmigration of T cells to muscle
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Initial injury ↓
muscle auto antigen release↓
Ag presentation by macrophages to CD4+ TH cells
↓Activated TH cells stimulate
macrophages (IFN-γ)↓
inflammatory mediator release
(: IL-1 and TNF-α)
↑expression of MHC proteins by myocytes
↓Auto-Ag is presented in association with MHC-I molecules on surface of
Myocytes↓
destruction of myocytes byCD8 cytotoxic T cells
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Role of non-immune processes
• marked structural changes in muscle fibers in the absence of any inflammatory cells
• lack of correlation between degree of inflammation and degree of muscle weakness
• Some, do not respond to anti-inflammatory therapy
• steroid treatment may eliminate inflammatory cells but may not improve clinical disease
• disease may progress when identifiable inflammation has subsided
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Iran Study
Manifestations at onset:
muscle weakness (45%) arthralgia (38%) myalgia (21%) specific rash (25%) fever (16%)
Manifestations during the disease course:
98%: proximal weakness
40-60%: arthralgia, arthritis, Fever, fatigue, weight loss, myalgia, heliotrope rash
20-40%: hair loss, dysphagia, articular rash, eyelids edema,malar rash, pulmonary involvement, Raynaud's phenomenon
<20%: muscular edema, cardiac manifestations, joint deformities, periungual erythema, calcinosis
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Diagnosis
clinical laboratory electromyography biopsy
exclusion of other disorders with similar features
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Laboratory evaluation
Serum muscle enzyme and Abs
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Serum muscle enzymes
↑in most patients
creatine kinase (CK) [early-late, DM/IBM-PM]
lactate dehydrogenase (LDH), Aldolase and aminotransferases
IBM: typically moderate CK↑ (< x10 normal)
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Autoantibodies
Present in a majority (~ 80% of PM/DM)
ANA: ↑↑ suggest presence of another CTD
Myositis-specific autoantibodies:
• anti-histidyl-tRNA synthase (: anti-Jo-1) • anti-signal recognition particle (anti SRP)• anti-Mi-2
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Electromyography (EMG)
evidence of muscle irritability
classic triad:• Increased insertional activity and spontaneous
fibrillations• Abnormal myopathic motor potential (low amplitude, short–duration polyphasic)• Complex repetitive discharges
Non-specific
Normal in ~ 10%
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Tissue biopsies
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Biopsy in DM
Skin and/or muscle biopsies may establish the diagnosis
Skin biopsy sufficient to confirm DM if: • typical weakness pattern (symmetric; proximal > distal) +• serum muscle enzymes↑ +• classic cutaneous findings
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Muscle biopsy in PM
Even in clinical scenarios highly consistent with PM, muscle biopsy is essential to establishing correct diagnosis and excluding other disorders
Open biopsy is preferred to needle biopsy
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Magnetic resonance imaging (MRI)
Useful in:
• identify biopsy site
• longitudinal follow-up (Tx response assessment, flares diagnosis)
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Classification Criteria
• 1. Symmetrical weakness Limb-girdle and neck flexors, with or without dysphagia/respiratory sx
• 2. Biopsy
• 3. Elevation of muscle enzymes in serum CK, aldolase, LDH, AST, ALT
• 4. EMG evidence
• 5. Dermatologic features Gottron’s sign, heliotrope rash, shawl sign, etc.
Polymyositis
4 criteria, no rash3 criteria, no rash2 criteria, no rash
Dermatomyositis
Rash + 3 criteriaRash + 2 criteriaRash + 1 criteria
DefiniteProbablePossible
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Differential Diagnosis
• Other myopathies
• Neuropathies
• Assosiations (collagen-vascular disease, malignancy)
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Malignancy
Can be diagnosed before, with, or after IIM diagnosis
Cancer site in 70% of cases:cervix, lung, ovaries, pancreas, bladder, and stomach
RISK FACTORS:
DM Capillary damage on muscle (especially with trunk cutaneous necrosis) biopsy
Cutaneous leukocytoclastic vasculitis Age >65 y at diagnosis
Evaluation:
• history, physical examination
• Age-appropriate cancer screening tests (: mammography and colonoscopy)
• CT of chest, abdomen and pelvis for high risk patients
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Initial therapy
• Prednisone: 1 mg/kg/day (≤ 80 mg/d)
• Severely ill patients→ methylprednisolone pulse
• taper to lowest effective dose over a total of 9 - 12 m
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Glucocorticoid-sparing agents
Initiate with GCs
First-line: azathioprine (AZT) or methotrexate (MTX)
Response: importance of muscle strength > muscle enzymes
Taper off GCs before tapering AZT/MTX (careful follow-up for possibility of disease recurrence )
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Resistant Disease
Consider several potential scenarios:
• Incorrect original diagnosis
• glucocorticoid-induced myopathy
• Underlying malignancy
Treatment
Rituximab Intravenous immune globulin Tacrolimus CyclosporineMycophenolate mofetil CyclophosphamideCombination therapy TNF inhibitors
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General treatment measures
• Early physical therapy and rehabilitation
• Aspiration precautions
• DM may be photosensitive → avoid UV
• Bisphosphonate from the start of treatment
• Sufficient Ca and Vitamin D intake
• high-dose prednisone + immunosuppressive → Pneumocystis jirovecii prophylaxis
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Outcome Predictors:
Type of myositis disease severitydelay in diagnosis autoantibody profile
Response to GCs alone: overlap myositis > DM > PM
Antisynthetase Ab: often associated with ILD and a worse prognosis
IBM: more resistance to treatment Progress gradually over a period of years By 15 y, most patients require assistance with basic daily activities
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