Idiopathic Inflammatory Myopathies PDF

Idiopathic Inflammatory Myopathies (IIM) Dr. Istabraq satam MBChB, F.I.B.M.S Rheum. &Med. Rehab.  Differential Diagnosis of Myopathies Idiopathic inflammatory myopathies (IIM) Miscellaneous  Neu...

Idiopathic Inflammatory Myopathies (IIM) Dr. Istabraq satam MBChB, F.I.B.M.S Rheum. &Med. Rehab.  Differential Diagnosis of Myopathies Idiopathic inflammatory myopathies (IIM) Miscellaneous  Neuromuscular disorders Infectious myositis  Sarcoidosis Organ failure (uremia, liver failure)  Muscular dystrophies (e.g., Duchenne’s)  Amyloidosis  Acute rhabdomyolysis  Neuromuscular junction disorders (e.g., Metabolic myopathies myasthenia gravis,)  Glycogen storage diseases (e.g., McArdle’s or  Bacterial (Staphylococcus, Streptococcus, myophosphorylase Borrelia burgdorferi) deficiency, acid maltase deficiency)  Nutritional disorders (malabsorption, vitamin D and E  Viral (e.g., HIV, adenovirus, influenza) deficiencies)  Parasitic (e.g., Toxoplasma, Trichinella, Taenia)  Electrolyte disorders (hypocalcemia and hypercalcemia, Endocrine disorders hypokalemia, hypophosphatemia)  Hypothyroidism (may see CK as high as 3000)  Hyperthyroidism  Acromegaly  Cushing’s disease  Addison’s disease  How are the idiopathic inflammatory myopathies (IIM) classified? 1. Adult-onset DM  DM  Amyotrophic DM 2. Adult-onset PM. 3.Overlap myositis  ASA  Myositis associated with other connective tissue diseases 4. Immune-mediated necrotizing myositis (IMNM) 5. IBM 6. Juvenile-onset DM (JDM)  Case scenario A 50-year-old woman is admitted by the medical team with muscle weakness. Her symptoms began insidiously over the last few weeks, but are now so severe she finds it hard to climb stairs or raise her arms above her head. Fine movements and grip strength are unaffected. She Otherwise she history of breast ca operated on and now on biological treatment ( Herceptin).  EPIDIMYOLOGY Annual incidence of 2–19 cases/million. Peak age of onset is bimodal in distribution for DM: one peak at 5 to 15 years of age, and the other at 45 to 65 years. PM in 50to 60 years. The female to male ratio is 2 to 3:1 overall. The female to male ratio in JDM is close to 1:1.  Clinical features Symmetrical proximal muscle weakness over a few weeks, usually affecting the lower limbs more than the upper. Ocular and facial motor weakness is strikingly unusual and should make one consider another diagnosis. Pain is typically absent or minimal pharyngeal muscles causing dysphonia and upper esophageal muscles causing dysphagia (sign of severity) Interstitial lung disease in up to 30% of patients and is strongly associated with the presence of antisynthetase (Jo-1) antibodies.  Dermatomyositis Presents similarly to PM ,but in combination with characteristic skin lesions. the skin lesions include:  Gottron’s papules, which are scaly, erythematous or violaceous, psoriasiform plaques occurring over the extensor surfaces of PIP and DIP joints  Heliotrope rash violaceous discoloration of the eyelid in combination with periorbital oedema  Shawl sign Shawl sign  V sign V sign  Dilatation of nail fold capillaries Periungual nail-fold capillaries are enlarged and tortuous  Threefold increased risk of malignancy in patients with dermatomyositis and polymyositis. This may be apparent at the time of presentation, but the risk remains increased for at least 5 years following diagnosis.  Investigations Serum levels of CK are usually raised and are a useful measure of disease activity. ALT ,AST ,and aldolase can be also elevated. EMG: myopathy and exclude neuropathy. MRI: areas of abnormal muscle for biopsy. Muscle biopsy: typical features of fiber necrosis, regeneration and inflammatory cell infiltrate. Screening for underlying malignancy should be undertaken routinely, and should include chest/abdomen/pelvis CT, gastrointestinal tract imaging and mammography (in women)  Management  Oral corticosteroids (e.g. prednisolone 40-60 mg daily)  High-dose intravenous methylprednisolone (1 g/day for 3 days) may be required in patients with respiratory or pharyngeal weakness.  Reduce steroids monthly to a maintenance dose of 5-7.5 mg.  Most Patients need additional immunosuppressive therapy: Azathioprine and methotrexate, ciclosporin, cyclophosphamide, tacrolimus or MMF.  Intravenous immunoglobulin in refractory cases.  Relapses may occur associated with a rising CK, and indicate the need for additional therapy. How do you separate steroid myopathy from a IIM exacerbation? Patients with IIM initially responding to prednisone may later complain of weakness while maintained on prednisone, especially when >20 mg/day. look at the CPK. Steroid myopathy does not cause an elevated CPK or aldolase because it causes muscle fiber atrophy, whereas IIM causes inflammation with muscle fiber injury causing release of muscle enzymes, including CPK. If still not certain, a muscle MRI will identify if active inflammation is still present.  What is amyopathic DM? Occasionally, the cutaneous manifestations of DM occur in the absence of clinically apparent muscle involvement, Perhaps half or more of such patients will develop muscle disease over time, but a significant proportion will manifest skin-limited disease only. Antisynthetase antibody (ASA) syndrome Proximal muscle weakness is typically the first manifestation Mechanic’s hand is common: characterized by cracking and fissuring of the skin of the finger pads, especially the radial side of the index finger. ILD, arthritis, Raynaud’s phenomenon, and fever can also occur  Immune-mediated necrotizing myositis (IMNM) Muscle disease predominates with acute or subacute onset of progressive proximal muscle weakness, myalgias, very high CPK >10 to 50 times upper limit of normal. No ILD or rash. Muscle histology: scattered necrotic fibers with macrophages. Minimal inflammatory infiltrate. Prognosis guarded. May be refractory to therapy  What is IBM? This is the most common IIM in patients aged >50 years  Juvenile dermatomyositis The most common inflammatory myopathy in children and adolescents, and typically does not require a search for malignancy. median age of onset of 7 years. Many clinical features are similar to those in the adult disease. JDM can be monocyclic, lasting up to 3 years (25–40%), or polycyclic, with periods of remission and relapse (60–75%). In some cases, polycyclic JDM can be chronic and life-long As in adults, calcinosis occurs in about 30%. Same lines of treatment. Case scenario  Case scenario INVESTIGATIONS Haemoglobin 14.2 g/dL( 13.3–17.7 g/dL) White cell count 8.2 ¥ 109/L( 3.9–10.6 ¥ 109/L) Platelets 342 ¥ 109/L (150–440 ¥ 109/L) Creatine kinase 3542 iU/L( 25–195 iU/L) ESR 73 mm/ /h  What is the diagnosis in this case? How would you further manage this patient?