PA13: Two cases of amyopathic juvenile dermatomyositis associated with antitranscription intermediary factor 1 gamma autoantibodies

A. Dubois, S. Sampath, S. Natarajan and C. Goodhead

Royal Victoria Infirmary, Newcastle upon Tyne, UK

Juvenile dermatomyositis (JDM) is a rare chronic childhood-onset autoimmune condition characterized by proximal muscle weakness in conjunction with associated skin disease. In a subset of children, skin features predominate and there is no muscle involvement. We present two patients with this rare phenotype. A 12-year-old boy presented with a 2-year history of an erythematous rash around both eyes, and widespread calcified papules affecting the elbows, knees, external ears and right upper eyelid. He was otherwise well, with no weakness or systemic symptoms. A poikilodermatous rash was noted on the eyelids and upper cheeks. There was subtle bilateral infraorbital lipodystrophy. Examination of muscle strength was normal. He had an extensive workup. Skin biopsy confirmed the presence of calcinosis cutis, but other changes of dermatomyositis were not seen. Nailfold capillaroscopy showed grossly dilated loops and severe density loss, consistent with systemic inflammation. Blood tests, including an extended myositis panel, demonstrated positive transcription intermediary factor (TIF)-1γ, Ro-60 and striated muscle autoantibodies. Skeletal muscle enzymes and imaging (magnetic resonance imaging) was normal. A diagnosis of amyopathic JDM was made. The second patient, a 14-year-old boy, presented with long-standing erythematous plaques affecting his elbows, knees, knuckles, eyelids and cheeks, and facial lipodystrophy. He had no evidence of muscle weakness, but his muscle bulk was low, with a lean appearance to the limbs, and he had contractures to the elbows and knees. Skin biopsy showed acanthosis with a prominent subepidermal band of hyalinization and chronic perivascular inflammatory infiltrate. This patient also had positive TIF-1γ autoantibodies and normal skeletal muscle enzymes and imaging, leading to a diagnosis of amyopathic JDM. Interestingly, both patients had anti-TIF-1 autoantibodies, a similar age of presentation, no muscle involvement and the same facial features. TIF-1 antibodies are reported to occur most often in young white patients, and can be associated with cutaneous ulceration and greater muscle weakness, which our patients did not have. Extensive calcinosis, as seen in the first patient, is more likely to be associated with antinuclear matrix protein (NXP2) autoantibodies. Both patients have recently started treatment, initially with corticosteroids, followed by methotrexate and hydroxychloroquine. The first patient is also receiving monthly intravenous immunoglobulin for resistant disease. Depending on response to treatment we will continue to explore other differentials such as interferonopathies. Our two patients demonstrated a rare combination of anti-TIF-1 antibody, amyopathic JDM and lipodystrophy, with and without calcinosis.