Classification & external resources
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Polymyositis is a type of inflammatory myopathy, related to dermatomyositis and inclusion body myositis. Polymyositis means 'many muscle inflammation'.
Additional recommended knowledge
Polymyositis tends to become evident in adulthood, presenting with bilateral proximal muscle weakness, often noted in the upper legs due to early fatigue while walking. Sometimes the weakness presents itself by the person being unable to rise from a seated position without help, or inability to raise their arms above their head. The weakness is generally progressive, accompanied by lymphocytic inflammation (mainly cytotoxic T8 lymphocytes). The cause is unknown, but seems to be related to autoimmune factors, genetics, and perhaps viruses. In rare cases, the cause is known to be infectious, associated with the pathogens that cause Lyme disease, toxoplasmosis, and others.
Polymyositis, like dermatomyositis, strikes females with greater frequency than males. The skin involvement of dermatomyositis is absent in polymyositis.
Diagnosis is fourfold, including elevation of creatine kinase, signs and symptoms, electromyograph (EMG) alteration, and a positive muscle biopsy. Treatment generally involves glucocorticoids, especially prednisone. At present, a number of studies are underway to determine whether patients diagnosed with polymyositis will benefit from newer drugs inhibiting the biologic effects of TNF alpha, such as infliximab.
Sporadic inclusion body myositis (sIBM): IBM is often confused with (misdiagnosed as) polymyositis and polymyositis that does not respond to treatment is likely IBM. sIBM comes on over months to years, polymyositis comes on over weeks to months. It appears that sIBM and polymyositis share some common features, especially the initial sequence of immune system activation, however, polymyositis does not display the subsequent muscle degeneration and protein abnormalities as seen in IBM. As well, polymyositis tends to respond well to treatments, IBM does not. IBM and polymyositis apparently involve different disease mechanisms than are seen in dermatomyositis.
- Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL. Harrison's Principles of Internal Medicine. New York: McGraw-Hill, 2005. ISBN 0-07-139140-1
|Diseases of the musculoskeletal system and connective tissue (M, 710-739)|
|Arthropathies||Arthritis (Septic arthritis, Reactive arthritis, Rheumatoid arthritis, Psoriatic arthritis, Felty's syndrome, Juvenile idiopathic arthritis, Still's disease) - crystal (Gout, Chondrocalcinosis) - Osteoarthritis (Heberden's node, Bouchard's nodes)
acquired deformities of fingers and toes (Boutonniere deformity, Bunion, Hallux rigidus, Hallux varus, Hammer toe) - other acquired deformities of limbs (Valgus deformity, Varus deformity, Wrist drop, Foot drop, Flat feet, Club foot, Unequal leg length, Winged scapula)
patella (Luxating patella, Chondromalacia patellae)
Protrusio acetabuli - Hemarthrosis - Arthralgia - Osteophyte
|Polyarteritis nodosa - Churg-Strauss syndrome - Kawasaki disease - Hypersensitivity vasculitis - Goodpasture's syndrome - Wegener's granulomatosis - Arteritis (Takayasu's arteritis, Temporal arteritis) - Microscopic polyangiitis - Systemic lupus erythematosus (Drug-induced) - Dermatomyositis (Juvenile dermatomyositis) - Polymyositis - Scleroderma - Sjögren's syndrome - Behçet's disease - Polymyalgia rheumatica - Eosinophilic fasciitis - Hypermobility|
|Dorsopathies||Kyphosis - Lordosis - Scoliosis - Scheuermann's disease - Spondylolysis - Torticollis - Spondylolisthesis - Spondylopathies (Ankylosing spondylitis, Spondylosis, Spinal stenosis) - Schmorl's nodes - Degenerative disc disease - Coccydynia - Back pain (Radiculopathy, Neck pain, Sciatica, Low back pain)|
|Soft tissue disorders||muscle: Myositis - Myositis ossificans (Fibrodysplasia ossificans progressiva)
synovium and tendon: Synovitis - Tenosynovitis (Stenosing tenosynovitis, Trigger finger, DeQuervain's syndrome)
bursitis (Olecranon, Prepatellar, Trochanteric)
fibroblastic (Dupuytren's contracture, Plantar fasciitis, Nodular fasciitis, Necrotizing fasciitis, Fasciitis, Fibromatosis)
enthesopathies (Iliotibial band syndrome, Achilles tendinitis, Patellar tendinitis, Golfer's elbow, Tennis elbow, Metatarsalgia, Bone spur, Tendinitis)
other, NEC: Muscle weakness - Rheumatism - Myalgia - Neuralgia - Neuritis - Panniculitis - Fibromyalgia
|Osteopathies||disorders of bone density and structure: Osteoporosis - Osteomalacia - continuity of bone (Pseudarthrosis, Stress fracture) - Monostotic fibrous dysplasia - Skeletal fluorosis - Aneurysmal bone cyst - Hyperostosis - Osteosclerosis|
Osteomyelitis - Avascular necrosis - Paget's disease of bone - Algoneurodystrophy - Osteolysis - Infantile cortical hyperostosis
|Chondropathies||Juvenile osteochondrosis (Legg-Calvé-Perthes syndrome, Osgood-Schlatter disease, Köhler disease, Sever's disease) - Osteochondritis - Tietze's syndrome|
|See also congenital conditions (Q65-Q79, 754-756)|