Information about Dermatomyositis

Classification & external resources

X-Ray of the knee in a patient with dermatomyositis.
ICD-10	M33.0-M33.1
ICD-9	710.3
DiseasesDB	10343
MedlinePlus	000839
eMedicine	med/2608  derm/98
MeSH	D003882

Dermatomyositis is connective-tissue disease that is characterized by inflammation of the muscles and the skin. Its cause is unknown, but it may result from either a viral infection or an autoimmune reaction. Up to 50% of the cases may be a paraneoplastic phenomenon, indicating the presence of cancer.

X-ray findings include dystrophic calcifications in the muscles.

There is a form of this disorder that strikes children, known as juvenile dermatomyositis.

"Gottron's papules", pink patches on the knuckles, and priapism, are associated with this disorder.

Pathology

The diagnosis of dermatomyositis can be confirmed by muscle biopsy. There are two classic microscopic findings of dermatomyositis. They are:

• A mixed B- and T-cell perivascular inflammatory infiltrate
• Perifascicular muscle fiber atrophy

Microscopic findings

Cross sections of muscle reveal muscle fascicles with small, shrunken polygonal muscle fibers on the periphery of a fascicle surrounding central muscle fibers of normal, uniform size.

Aggregates of mature lymphocytes with small, dark nuclei and scant cytoplasm are seen surrounding vessels. Other inflammatory cells are distinctly uncommon. Immunohistochemistry can be used to demonstrate that both B- and T-cells are present in approximately equal numbers.

Mechanism

The mechanism is conjectured to be complement-mediated damage of microscopic vessels with muscle atrophy and lymphocytic inflammation secondary to tissue ischemia ^[1].

Differential diagnosis

Dermatomyositis must be differentiated from other common, lymphocyte predominant inflammatory myopathies. If present, the characteristic perifascicular atrophy makes this distinction trivial.

There is some overlap in the microscopic appearances of different inflammatory myopathies, but some helpful differences are often present.^[2] The rimmed vacuoles of inclusion body myositis (IBM) are absent in dermatomyositis. Polymyositis is characterised by diffuse or patchy inflammation of the muscle fascicles, a random pattern of muscle atrophy, and T-cell predominance with T-cells seen invading otherwise viable appearing muscle fibers.^[1]

Signs

Periorbital Heliotrope Rash (HELIOTROPE RASH: purple /erythematous rash affecting eyelids, malar, forehead and nasolabial folds), Gottron's papules at the knuckles (Purple /erythematous raised lesions over knuckles and extensor regions).

Treatment

• 1. High Dose Prednisolone
• 2. Methotrexate (complication: may cause Interstitial lung disease)
• 3. IVIG
• 4. Azathioprine
• 5. Cyclophosphamide

References

1. ^  Benveniste O, Squier W, Boyer O, Hilton-Jones D, Herson S. Presse Med. 2004 Nov 20;33(20):1444-50. PMID: 15611679
2. ^  Nirmalananthan N, Holton JL, Hanna MG. Is it really myositis? A consideration of the differential diagnosis. Curr Opin Rheumatol. 2004 Nov;16(6):684-91.

External links

• The American College of Rheumatology's patient education page on myopathy
• Illustration of Gottron's papules

•  • [ e] Muscular Dystrophy
The Nine Primary Muscular Dystrophies	Becker's • Congenital • Duchenne • Distal • Emery-Dreifuss • Facioscapulohumeral • Limb-girdle muscular dystrophy • Myotonic • Oculopharyngeal
Related topics
National/International Organizations	Muscular Dystrophy Association (USA) . Muscular Dystrophy Canada
US government Institutes and Legislation	NINDS • NIAMS • NICHD • MD CARE Act • Genetic Information Nondiscrimination Act • Americans with Disabilities Act of 1990
National/International Events	Jerry Lewis MDA Telethon (USA)
Recent or Ongoing Clinical Trials	Stamulumab (MYO-029)

•  • [ e] Diseases of the musculoskeletal system and connective tissue (, )
Arthropathies	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) - Chondromalacia patellae
Systemic connective tissue disorders	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 - Sjgren's syndrome - Behet's disease - Polymyalgia rheumatica - Eosinophilic fasciitis - Hypermobility
Dorsopathies	Kyphosis - Lordosis - Scoliosis - Scheuermann's disease - Spondylolysis - Spondylolisthesis - Spondylopathies (Ankylosing spondylitis, Spondylosis, Spinal stenosis) - Schmorl's nodes - Degenerative disc disease - Coccydynia - Back pain (Radiculopathy, Sciatica, Lumbago, Low back pain)
Soft tissue disorders	Myositis - Myositis ossificans (Fibrodysplasia ossificans progressiva) - 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, Golfer's elbow, Tennis elbow, Metatarsalgia, Bone spur, Tendinitis) - Myalgia
Osteopathies	Osteoporosis - Pseudarthrosis - Stress fracture - Monostotic fibrous dysplasia - Skeletal fluorosis - Aneurysmal bone cyst - Osteomyelitis - Avascular necrosis - Paget's disease of bone - Algoneurodystrophy - Osteolysis
Chondropathies	Juvenile osteochondrosis (Legg-Calv-Perthes syndrome, Osgood-Schlatter disease, Khler disease, Sever's disease) - Tietze's syndrome
See also conditions (Q65-Q79, )