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Interstitial lung disease (ILD) is associated with several connective tissue diseases including dermatomyositis. Dermatomyositis typically presents with muscle weakness and various skin abnormalities such as Gottron papules and heliotrope rash. The link between dermatomyositis and ILD is seen most commonly in antisynthetase syndrome with anti-Jo-1 being the predominant antibody. However, melanoma differentiation-associated gene 5 (MDA5) amyopathic dermatomyositis portends an increased risk of ILD with rapid progression of disease. We present a patient with dermatomyositis and associated ILD that was found to have anti-MDA5 antibodies.CASE PRESENTATION: A 65-year-old woman with a history of chronic hepatitis B infection presented to our facility with progressively worsening necrotic skin lesions over bilateral hands, elbows, and forehead for six months. Two months prior to presentation, she underwent biopsy of a lesion on the palmar surface of the second digit which revealed superficial perivascular dermatitis with vascular ectasia and basement membrane thickening consistent with Gottron's papules. Based on these findings and absence of myositis, diagnosis of amyopathic dermatomyositis was suspected. Autoimmune serologies including antinuclear antibodies, anti-Scl-70 antibodies, and anti-Jo-1 antibodies were negative while anti-MDA5 antibodies were strongly positive, confirming the diagnosis of MDA5 amyopathic dermatomyositis. A screening chest CT without contrast showed diffuse reticular opacities in a peribronchovascular distribution consistent with nonspecific interstitial pneumonia pattern of ILD. She was started on prednisone and mycophenolate mofetil with close outpatient pulmonary follow up.DISCUSSION: MDA5 amyopathic dermatomyositis presents with characteristic cutaneous ulcerations, arthritis and arthralgias, and rapidly progressive ILD in the absence of other typical antibodies associated with dermatomyositis. Viral infection is thought to be a common trigger resulting in MDA5 driven production of type I interferons that leads to cell death. CT chest should be performed to screen for ILD as 42-100% patients have rapid progression of disease that is associated with high mortality. Treatment is usually aggressive immunosuppression with steroids and steroid sparing agents. For refractory cases, IVIG and rituximab have been used with success. Anti-MDA5 antibodies are reported in less than 10% of patients with dermatomyositis. As such, screening for these antibodies plays an important role in identifying patients at risk for ILD.CONCLUSIONS: This case highlights the importance of screening for MDA5 antibodies in patients with suspected dermatomyositis. ILD is associated with a high rate of mortality and requires prompt immunosuppression.

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