**4.1.1 Soft tissue abnormalities**

**4.1.1.1** Soft tissue calcifications may be preceded by oedema of the subcutaneous tissue and muscle, causing increased muscular bulk and radiodensity, thickening of subcutaneous septa and poor definition of the subcutaneous tissue-muscle interface. These features may be detected on radiographs specifically exposed to show soft tissue to better advantage. Present day digital radiography generally shows the soft tissue far more optimally, as compared to film radiography, and even an incidental diagnosis of subtle changes of dermatomyositis may be established more readily with modern digital imaging (Fig. 3h). CT is more sensitive than MRI for demonstrating soft tissue calcifications, however, CT is rarely indicated.

**4.1.1.2** The changes are more prominent in the proximal musculature, axilla, chest wall, forearms, thighs and calves (Fig. 3b-e).

**4.1.1.3** Following on effective treatment, the soft tissue oedema may decrease or disappear entirely. However, fibrosis, muscle atrophy and contractures may develop later. There tends to be decreased soft tissue and muscular bulk, increased translucency of the soft tissue, osteopaenia, calcification and sometimes eventual contractures.

**4.1.1.4** Soft tissue calcification occurs in 30—70% of children and 10% of adults, and may occur within the first year of the illness (Moses, 2008). The extent of calcification, especially within the muscles, appears to increase with the severity of the illness. Small or large calcareous intramuscular fascial plane calcification is distinctive of dermatomyositis and polymyositis, though subcutaneous calcification is more common. The large muscles of the proximal parts of the extremities are more frequently affected. Sheetlike confluent calcifications especially occur in the thigh (particularly the vastus lateralis) (Fig. 2c), the pelvic girdle, the upper extremity (deltoid muscles, especially), and the flexor muscles of the neck. Further areas include the elbows, knees, hands, chest and abdominal wall, axillary and inguinal regions.

**4.1.1.5** There are four distinct patterns of soft tissue calcifications that occur in childhood dermatomyositis; deep calcareous masses, superficial calcareous masses, deep linear deposits and lacy, reticular, subcutaneous collections that encase the torso. The deep deposits are more commonly encountered (Resnick & Kransdorf, 2005).

**4.1.1.6** The amorphous calcifications of dermatomyositis should be differentiated from the bone formation in myositis ossificans, where native bone with immature trabecular bone centrally surrounded by compact bone may be seen.

**4.1.1.7.1** The term 'milk of calcium' has been used to describe calcium-laden fluid collections in the gall bladder and kidney and more recently by US, in the soft tissue of the

seen.

treatment.

pneumonia.

honeycomb pattern may form.

**4.3 Cardiac abnormalities** 

pericarditis (O'Brien & Kelleher, 2008).

**4.4 Gastrointestinal abnormalities** 

pathologically, are not detected radiographically.

thickening and irregularity was frequently encountered.

**4.2 Pulmonary involvement** 

however, may also be seen in isolation.

myositis may, furthermore, affect the diaphragm directly.

Dermatomyositis 141

**4.1.2.3** Arthralgias and arthritis are present in 20-50% of patients with the wrists, knees and small joints of the fingers affected symmetrically. Permanent joint changes are infrequently

**4.2.1** Lung changes will occur in up to 50% of patients, and aspiration pneumonia is probably the most common finding seen on chest X-rays (Fig. 1a). Aspiration is due to cough impairment, dysfunction of the pharynx and general weakness relating to body movement (Fig. 3a). Weakness of the respiratory muscles is associated with stiffness of the lungs, small lung volumes and diaphragmatic elevation with basal plate atelectasis. The

**4.2.2** Pulmonary arterial hypertension, with large main and proximal pulmonary arteries, may occur as a complication of interstitial lung disease, hypoventilation or vasculitis,

**4.2.3** Interstitial fibrosis was first described in 1956, is now well recognised and occurs in 5- 10% of patients (Hansell, et al., 2005). (It correlates strongly with the presence of anti-Jo-1, a myositis specific autoantibody.) The illness may be acute, rapidly fatal and resistant to therapy, or benign, indolent and asymptomatic, with favourable response to steroid

**4.2.4** The more acute patients may demonstrate airspace opacity or even widespread groundglass shadowing, with alveolar opacities earlier in the course and more likely to be steroid responsive. These changes are likely to be predominantly due to organising

**4.2.5** Radiographic changes often consist of symmetric reticulonodular changes, mostly in the base of the lungfields. In time the entire lungfields may be involved and a fine

**4.2.6** The chest X-ray may be normal, despite the presence of confirmed clinical disease. Multifocal dystrophic pulmonary ossifications, which have been demonstrated

**4.2.7** High-resolution CT changes consist principally of groundglass opacification, diffuse but patchy, mostly peripheral, and also parenchymal bands and consolidation. Bronchiectasis occurs in 40% of patients, though honeycombing was uncommon. Pleural

**4.3.1** The myocardium may be affected in a similar way to the involvement of skeletal striated muscle. Cardiac complications include arrhythmias, congestive cardiac failure, and

**4.4.1** Patients may complain of dysphagia and a barium swallow may reveal disordered peristalsis involving the upper oesophagus, that portion with striated muscle. [The lower

subcutaneous and intermuscular regions of the thigh and calf in two patients with childhood dermatomyositis (Hesla, et al., 1990). Case 2 (Fig. 2e) presents similar features except that fluid-calcium layering (the sedimentation sign) was also demonstrated with an unusually long level indicating the flattened elongated shape of the collection. There was also localized tenderness and this prompted aspiration, even though from a US point of view the fluid-calcium level militated against a soft-tissue abscess.

**4.1.1.7.2** Complications of diagnostic and therapeutic aspiration of such collections include introducing secondary infection and secondly the formation of a chronic sinus tract. The latter could result especially if a large bore needle was used to penetrate the frequently hard, brittle subcutaneous calcified tissues. If possible, formal surgical incision and drainage should therefore also be avoided.

**4.1.1.7.3** Most conventional radiographic studies fail to show the layering as they are not taken with a horizontal ray beam.

**4.1.1.7.4** The diagnosis of fluid-calcium layering can also be established by CT or MRI, when associated bony changes can also be assessed. However, in the absence of skeletal changes on conventional radiographs, US is thought to be more expeditious, less expensive, readily available and no ionizing radiation is involved, especially in childhood dermatomyositis. (Van Gelderen, 2007).

**4.1.1.8** Abnormal accumulation of technetium polyphosphate in affected muscle (nuclear medicine study) was a useful technique, however this has now been superceded by MRI, with MRI more accurate and not employing ionizing radiation. Signal intensity would alternate according to the activity of the disease, and therefore changes in the signal pattern were useful to monitor response to treatment. MRI may allow the correct diagnosis of dermatomyositis (or polymyositis) to be made where muscle involvement is not detected clinically (Resnick & Kransdorf, 2005). T2-weighted imaging may be used, but fatsuppressed imaging and STIR-MRI are particularly optimal (Fig. 3b-e). The calcific mass might be of low signal but the affected muscle and perimuscular oedema would be hyperintense, and return to normal after treatment. Follow-up STIR MRI had shown no improvement in Case 3. Phosphorus-31 MR spectroscopy may be used for quantitative characterisation of inflammatory disease. (Park, et al., 1990). MRI may also aid in the clinical dilemma of differentiation between myositis from persistent steroid dermatomyositis.

#### **4.1.2 Articular abnormalities**

**4.1.2.1** Transient radiographic features with soft tissue swelling and periarticular osteopaenia may be present, but bony erosive changes are uncommon and may involve the metacarpophalangeal and interphalangeal joints. Periosteal and soft tissue calcifications with flecks or small clumps of calcium may be detected on radiographs of the hands. (Fig. 2b). Rheumatoid-like changes are, however, uncommon. The 'floppy-thumb' sign may be detected with radial subluxation or dislocation of the interphalangeal joint of the thumb.

**4.1.2.2** Acroosteolysis with pointing and resorption of the terminal tufts of the fingers may occur uncommonly, but reduced soft tissue relating to the tips of the fingers is less infrequent. (Fig. 2b). Flexion contractures and soft tissue ulceration may involve the fingers, though larger joints may be involved.

subcutaneous and intermuscular regions of the thigh and calf in two patients with childhood dermatomyositis (Hesla, et al., 1990). Case 2 (Fig. 2e) presents similar features except that fluid-calcium layering (the sedimentation sign) was also demonstrated with an unusually long level indicating the flattened elongated shape of the collection. There was also localized tenderness and this prompted aspiration, even though from a US point of

**4.1.1.7.2** Complications of diagnostic and therapeutic aspiration of such collections include introducing secondary infection and secondly the formation of a chronic sinus tract. The latter could result especially if a large bore needle was used to penetrate the frequently hard, brittle subcutaneous calcified tissues. If possible, formal surgical incision and drainage

**4.1.1.7.3** Most conventional radiographic studies fail to show the layering as they are not

**4.1.1.7.4** The diagnosis of fluid-calcium layering can also be established by CT or MRI, when associated bony changes can also be assessed. However, in the absence of skeletal changes on conventional radiographs, US is thought to be more expeditious, less expensive, readily available and no ionizing radiation is involved, especially in childhood dermatomyositis.

**4.1.1.8** Abnormal accumulation of technetium polyphosphate in affected muscle (nuclear medicine study) was a useful technique, however this has now been superceded by MRI, with MRI more accurate and not employing ionizing radiation. Signal intensity would alternate according to the activity of the disease, and therefore changes in the signal pattern were useful to monitor response to treatment. MRI may allow the correct diagnosis of dermatomyositis (or polymyositis) to be made where muscle involvement is not detected clinically (Resnick & Kransdorf, 2005). T2-weighted imaging may be used, but fatsuppressed imaging and STIR-MRI are particularly optimal (Fig. 3b-e). The calcific mass might be of low signal but the affected muscle and perimuscular oedema would be hyperintense, and return to normal after treatment. Follow-up STIR MRI had shown no improvement in Case 3. Phosphorus-31 MR spectroscopy may be used for quantitative characterisation of inflammatory disease. (Park, et al., 1990). MRI may also aid in the clinical dilemma of differentiation between myositis from persistent steroid dermatomyositis.

**4.1.2.1** Transient radiographic features with soft tissue swelling and periarticular osteopaenia may be present, but bony erosive changes are uncommon and may involve the metacarpophalangeal and interphalangeal joints. Periosteal and soft tissue calcifications with flecks or small clumps of calcium may be detected on radiographs of the hands. (Fig. 2b). Rheumatoid-like changes are, however, uncommon. The 'floppy-thumb' sign may be detected with radial subluxation or dislocation of the interphalangeal joint of the thumb.

**4.1.2.2** Acroosteolysis with pointing and resorption of the terminal tufts of the fingers may occur uncommonly, but reduced soft tissue relating to the tips of the fingers is less infrequent. (Fig. 2b). Flexion contractures and soft tissue ulceration may involve the fingers,

view the fluid-calcium level militated against a soft-tissue abscess.

should therefore also be avoided.

taken with a horizontal ray beam.

(Van Gelderen, 2007).

**4.1.2 Articular abnormalities** 

though larger joints may be involved.

**4.1.2.3** Arthralgias and arthritis are present in 20-50% of patients with the wrists, knees and small joints of the fingers affected symmetrically. Permanent joint changes are infrequently seen.
