Concurrent Treatment With Rituximab and Plasma Exchange for Rapidly Progressive Interstitial Lung Disease Complicating Anti-MDA5 Antibody-Positive Juvenile Dermatomyositis.

A 2-year-old Japanese girl with a 2-month history of progressive muscle weakness of the limbs, dysphasia, and erythema on both cheeks presented with fever and respiratory distress with dry cough. Physical examination revealed respiratory sound attenuation with fine crackles bilaterally in the basilar lung area, mild muscular weakness of the proximal lower limbs, and typical skin symptoms including erythema on the nail circumference, heliotrope rash, and Gottron's papules. The laboratory findings were as follows: creatine kinase level of 48 U/L (reference range, 43–230), aldolase level of 10.1 IU/L (reference range, 2–6), C-reactive protein level of 0.16 mg/dL (reference range, <0.15), ferritin level of 130 ng/mL (reference range, 6.23–138), Krebs von den Lungen-6 level of 2703 U/mL (reference range, 105–435), and lactate dehydrogenase level of 480 U/L (reference range, 120–230). Antinuclear antibody and antiaminoacyl tRNA synthetase antibodies were not detected, but a high titer of antimelanoma differentiation-associated gene 5 antibody (anti-MDA5Ab)was observed (>1270 indexes; reference, <32). Chest computed tomography revealed reticular shadows and ground-glass opacity in the middle to the inferior fields of the bilateral lung with pleural effusion (Fig. A). Magnetic resonance imaging revealed that muscles in the lower limbs have increased signal intensity. She was diagnosed with rapidly progressive interstitial lung disease (RP-ILD) complicating anti-MDA5 Ab– positive juvenile dermatomyositis (JDM). The patient's disease was refractory to steroids including 2 courses of methylprednisolone pulse (30 mg/kg per day for 3 consecutive days) and dexamethasone palmitate, oral tacrolimus, intravenous cyclosporine, intravenous cyclophosphamide, and intravenous immunoglobulin (Fig. B, Supplement Figure, http:// links.lww.com/RHU/A195). After the additional combination treatment of rituximab (RTX) and plasma exchange (PE), ILD