A 14-year-old previously healthy boy presented with left periorbital swelling and redness for 1 year and muscle weakness and joint pain for 4 months.
On examination he had purple discoloration and swelling around the left eye (Figure 1(a) before therapy and Figure 1(b) after therapy), Gottron's papules over the metacarpophalangeal (MCP) joints bilaterally, and muscle weakness with a grade of 3/5 in the proximal group and 4/5 in the distal group. Workup revealed a normal CBC, ESR 33 mm/hr, and CRP 0.383 mg/L. Liver function test showed the following abnormalities: AST 281 U/L, ALT 95 U/L, GGT 24 U/L, ALP 149 U/L, and CK 4585 U/L. Antinuclear antibodies negative with ENA are all negative. Renal function test and thyroid function test were normal.
MRI muscle revealed diffuse muscle edema involving the muscles of the pelvis, thighs, legs, and upper extremities as well as the muscle of back suggestive of inflammatory myopathy.
CT orbital shows soft tissue swelling in the anteromedial and superior aspects of the left orbit which shows minimal enhancement in the postcontrast, there was an appearance of a left-sided preseptal periorbital cellulitis with no evidence of abscess formation. Biopsy from the lower lid revealed no malignant cells or acid fast bacilli with subsequent negative culture for tuberculosis after 8 weeks.
Muscle biopsy was performed and revealed mildly and focally increased endomysial and perimysial connective tissues. There was perivascular chronic inflammatory cells infiltration in the perimysial areas with few mononuclear inflammatory cells that were scattered in-between the muscle fibers. The muscle fibers showed mild to focally moderate variation of size and shapes and the majority had peripheral nuclei. Scattered foci of myofiber necrosis and regeneration were evident. Perifascicular atrophy was not a prominent feature, but it could be focally appreciated (Figure 1(c)). Ultrastructural examination revealed findings that were in keeping with light microscopy, including prominent myofibrillar disarray (Figure 1(d)). In addition, scattered rod-like structures and cytoplasmic bodies were detected. The overall features were in keeping with an inflammatory myopathy, with features suggestive of dermatomyositis.
Skin biopsy of the left lower lid showed evidence of mild hyperkeratosis in the epidermis. The dermis showed heavy chronic inflammation cell infiltration that consists mainly of lymphocytes and plasma cells, infiltrating the hair follicles. Adjacent mild dermal fibrosis, focal solar elastosis, and pigment incontinence are noted.
The patient was started on prednisolone 50 mg daily with an increasing dose of methotrexate 15 mg reaching 20 mg per week. At 6 months, the patient showed a dramatic improvement with normalization of muscle power, fading of the skin rashes, and reduction of muscle enzymes. As of April 2014, he is back to school with a normal performance on prednisolone 5 mg daily and methotrexate 20 mg weekly.