Dermatomyositis

Dermatomyositis is an autoimmune inflammatory myositis, which like its closely-related condition polymyositis, carries an increased risk of malignancy.

Epidemiology

There is a recognized female predilection. It has a bimodal age of presentation depending on the variant:

• juvenile dermatomyositis (JDM): affects children and tends to be more severe
• adult dermatomyositis (ADM): typically affects adults around the age of 50

Associations

• interstitial lung disease : typically gives a patchy and subpleural consolidation with parenchymal bands
• internal malignancy : can occur as part of a paraneoplastic syndrome (e.g. lung cancer)

Clinical presentation

The classic presentation is that of a symmetrical proximal myopathy with associated dermatological changes which includes a dusky-red rash over the face, arms, hands, legs and other features (e.g. Gottron papules). Dysphagia, myalgia, fever and weight loss are other features .

Complications

Malignancy

There is a sixfold increased risk of malignancy in dermatomyositis (cf. twofold in polymyositis) . Multiple risk factors for the development of malignancy have been identified :

• >60 years old
• male
• dysphagia
• necrosis of the skin
• cutaneous vasculitis
• accelerated onset of disease
• increased creatine kinase (CK) levels
• increased ESR and C-reactive protein (CRP) levels

Several factors decrease the risk of malignancy :

• interstitial lung disease (ILD)
• inflammatory arthropathy
• Raynaud syndrome
• anti-Jo-1 antibody 

Pathology

There is cell-mediated injury targeted at striated muscle with resultant atrophy, edema, coagulation necrosis, fibrosis and calcification.

Markers

• elevated muscle enzymes (e.g. CK)
• elevated muscle specific antibodies
  • anti-RNA
  • anti-Mi2

Subtypes

• hypomyopathic dermatomyositis
• clinically amyopathic dermatomyositis (CADM) / amyopathic dermatomyositis
  • anti-melanoma differentiation-associated gene 5 (MDA5) antibody-positive clinically amyopathic dermatomyositis (CADM) 

Radiographic features

Plain radiograph

• typically shows dystrophic calcification in muscles and soft tissues (calcinosis universalis)
  • sheet-like although at least four patterns have been described with childhood dermatomyositis
  • classically seen affecting the thigh regions
• chest radiograph may show diaphragmatic elevation
• acro-osteolysis

Fluoroscopy

Barium swallow

• may show disordered peristalsis involving the upper esophagus i.e. the portion supplied by skeletal muscle

MRI

• T2: generally hyperintense signal throughout the affected muscles; calcific areas may be low signal; perimuscular edema may additionally appear as high signal; signal intensity may return to normal after treatment

Differential diagnosis

General imaging differential considerations include:

• polymyositis: does not affect the skin

Practical points

MRI T2-weighted sequences are useful to guide muscle biopsy:

• areas of edema related to the active inflammatory process
• non-specific end-stage fatty atrophic muscle should be avoided 

Further imaging in the form of a contrast-enhanced CT of the chest, abdomen and pelvis may be undertaken to exclude an associated primary malignancy.

Siehe auch:

• Lungenkarzinom
• Akroosteolyse
• Interstitielle Lungenerkrankung
• Calcinosis cutis
• muskuloskelettale Manifestationen Dermatomyositis

und weiter:

• Sklerodermie Ösophagus
• inflammatorischer Pseudotumor der Orbita
• Systemische Sklerodermie
• Amyloidose
• subkutane Verkalkungen
• causes of pulmonary arterial hypertension
• bilaterale axilläre Lymphadenopathie
• gluteal injection site granuloma
• interstitial pneumonia
• calcinosis circumscripta
• retikuläres Muster
• Fibrodysplasia ossificans progressiva
• Myositis
• Muskelödem
• dystrophic calcification within the breast
• Rheuma Differentialdiagnose
• Bazex-Syndrom
• differential diagnosis of intramuscular high STIR signal on MRI
• radiologisches muskuloskelettales Curriculum
• dystrophic soft-tissue calcification
• dracunculiasis
• juvenile Dermatomyositis
• Merkspruch Weichteilverkalkungen