Case Presentation: Anti-melanoma differentiation-associated gene 5 dermatomyositis (MDA5-DM) is a subset of amyopathic dermatomyositis that may present with oral ulcerations, painful palmar papules, arthritis, and panniculitis.1 Unique characteristics of MDA5-DM versus other types of dermatomyositis include a higher incidence of interstitial lung disease (ILD), lower incidence of myositis, and a higher rate of morality. MDA5-DM can be difficult to diagnose and can be easily missed if it is not high on the differential. 25 year old female with a history of Raynaud’s syndrome and cutaneous lupus who initially presented to the emergency department (ED) for bilateral hand ulcerations and facial edema. The patient had multiple recent hospitalizations for infected skin ulcerations and also had a recent debridement and bursectomy of bilateral elbows, requiring IV antibiotics for four weeks. She also reported joint pain, weakness, and significant weight loss. These symptoms had all been progressively worsening since 2019 after her diagnosis of cutaneous lupus. In the ED, the patient was slightly tachycardic to 119, and initial labs were significant for erythrocyte sedimentation rate of 71 mm/hr. Physical exam showed periorbital swelling but no joint swelling. She also had hyperkeratotic dry nodules on the dorsal surfaces of her arms near the elbows. She was started on prednisone 7.5 mg, and rheumatology was consulted. Initial rheumatologic workup was positive for ANA multiplex with an IFA of < 1:80. Negative labs included anti Jo-1 antibody, RNP antibody, anti-Scl 70 antibody, anti-Sm antibody and anti-RNA polymerase III antibody. Anti-myeloperoxidase and anti-proteinase 3 were negative. Hepatitis C, B and HIV were all negative. X-rays of bilateral hands were negative for osteomyelitis. The patient was subsequently started on IV vancomycin and cefepime for a total of four weeks to cover for possible infection. The patient was discharged home shortly afterwards on prednisone 10 mg twice daily. A myositis panel was also collected.Patient was re-hospitalized a few weeks later for worsening upper extremity lesions. A CTA chest was performed which revealed a pleural effusion but no ILD. She was started on IVIG, and steroids were continued. After discharge, the patient’s anti-MDA-5 antibody returned elevated to 49 units. She was continued on monthly IVIG, daily prednisone, and was also started on mycophenolate mofetil (MMF) with subsequent improvement in her hand ulcerations.
Discussion: This case represents the challenge of diagnosing MDA5-DM. It took almost two years to arrive at an accurate diagnosis, after the patient was initially diagnosed with cutaneous lupus. Due to the difficulty of diagnosis, the disease prevalence is most likely underestimated.4 In a case report by Pacot et al., they found that there was a diagnostic delay of four months ultimately leading to death in some patients.4 MDA5-DM can be a devastating disease process given its rapid progression to ILD. A standard treatment for MDA5-DM has not been established, and most of the studies focus primarily on MDA5-DM with ILD. In this case, the patient was treated with MMF, resulting in clinical benefit.
Conclusions: This case emphasizes the difficulty in diagnosing MDA5-DM. However, it is imperative it is promptly diagnosed because the disease can quickly progress to ILD, possibly leading to death. Additionally, there needs to be standardization of care for MDA5-DM in patients without ILD.