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Acute oedematous dermatomyositis
  1. A E SMYTH,
  2. A L BELL
  1. Department of Rheumatology
  2. Musgrave Park Hospital
  3. Stockman's Lane
  4. Belfast BT9 7JB
  5. Northern Ireland
  6. Department of Radiology
  7. Musgrave Park Hospital
    1. M CRONE
    1. Department of Rheumatology
    2. Musgrave Park Hospital
    3. Stockman's Lane
    4. Belfast BT9 7JB
    5. Northern Ireland
    6. Department of Radiology
    7. Musgrave Park Hospital

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      There are many published reports of limb oedema occurring in various rheumatic diseases.1 It may be present in patients with dermatomyositis oedema, especially where the subcutaneous tissue is loose, such as the upper eyelids.2

      A 27 year old woman presented with an eight week history of a progressive increase in girth of both forearms and tightening of the overlying skin. Four weeks from onset she had developed a triad of cutaneous features: a periorbital heliotrope rash, an erythematous malar rash affecting the nasolabial folds, and a ‘V’ sign rash on her neck. Two weeks later proximal muscle weakness developed. Physical examination showed markedly oedematous forearms, the overlying skin was tense, and elbow extension limited. Nailfold capillary microscopy was abnormal showing disorganisation and dilatation. Neurological assessment showed grade 4 muscle power in hip flexors and shoulder abductors; other systems were normal.

      Investigations included a normal full blood picture, differential white cell count, C reactive protein, and erythrocyte sedimentation rate. Muscle enzymes were raised: creatinine kinase 1454 U/l (normal 0–195), serum aspartate aminotransferase 106 IU/l (7–40), serum alanine aminotransferase 77 IU/l (10–60), aldolase 6.1 U/l (0.5–3.1). Thyroid function was normal. Antinuclear antibody was negative, as were antibodies to extractable nuclear antigens and Jo-1. Virology for coxsackievirus, Epstein-Barr virus, cytomegalovirus, picornavirus, echovirus, parvovirus-19, influenza, and rubella and serology for trichinella and toxoplasma were all negative. Chest radiograph, electrocardiography, pulmonary function tests (lung volumes and transfer factor) were normal. An ultrasound scan of the abdomen and pelvis was normal. Tumour markers CEA and CA-125 were within normal limits. Electromyography of the right deltoid and biceps muscles showed a myopathic abnormality. A forearm muscle biopsy specimen showed perivascular inflammation, and a second full thickness biopsy specimen showed only patchy inflammation, with the deep fascia unaffected. A magnetic resonance (MR) scan of the forearm was performed on the arm that was not biopsied (fig 1). A T-2 weighted inversion recovery scan showed an extensive collection of fluid lying in the subcutaneous space adjacent to both extensor and flexor muscles (arrow A) with increased signal in the extensor digitorum muscles in keeping with myositis (arrow B).

      Figure 1

      Magnetic resonance scan of the forearm showing fluid in the subcutaneous space adjacent to extensor and flexor muscles (arrow A) and increased signal in the extensor digitorum muscles (arrow B).

      The diagnosis of dermatomyositis, suggested initially by the cutaneous stigmata and proximal myopathy, was confirmed by raised muscle enzymes, classical histological findings on muscle biopsy, and myopathic features on electromyography. Investigations to exclude other causes of an inflammatory myopathy or any associated malignancy were normal. There was a dramatic clinical response after the start of treatment with daily prednisolone (1 mg/kg) and azathioprine (2 mg/kg). Within 48 hours muscle power was completely restored and muscle enzymes returned to normal. Within 10 days both arms were normal in size and had a normal skin texture. Steroid treatment was cautiously reduced and discontinued six months from presentation; one month later azathioprine was stopped. This patient remains under review and has not had further symptoms at two years' follow up.

      Gross peripheral oedema represents an unusual presenting feature of dermatomyositis. Indeed the atypia of this additional physical sign in a case of otherwise classical dermatomyositis made the authors consider and exclude eosinophilic fasciitis as part of the differential diagnosis.

      Recently, the use of MR imaging has proved to be a useful adjunctive test for assessing disease activity, guiding therapeutic decisions, and aiding the selection of a site for muscle biopsy in inflammatory myopathies.3 In this case MR imaging provided radiological evidence as to the cause of the increase in forearm girth. The aetiopathogenesis of the free fluid seen is likely to be due to an increase in capillary permeability, a result of the intense inflammatory process in the underlying muscle. In acute polymyositis and dermatomyositis, MR imaging is known to show focally or inhomogeneously increased signal intensities on T-2 weighted images in affected muscles, which has been shown to correlate with disease activity, and returns to normal after successful treatment.3-6 Additionally, perimuscular oedema, which probably represents oedema of the fascia or adjacent tissue, and increased signal intensity in a reticular distribution in the subcutaneous fat, have been described.7

      Early diagnosis of polymyositis and dermatomyositis is often missed. This case thus illustrates a possible early clinical sign and furthermore, shows the use of MR imaging in this condition.

      References

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