Title: Rapid Respiratory Failure – A Rare Rheumatologic Emergency
Introduction: Clinically amyopathic dermatomyositis (CAMD) is a rare and underdiagnosed subset of the polymyositis/dermatomyositis spectrum. Several myositis-specific autoantibodies (MSAs) have been identified in recent years with significant clinical implications. The anti-MDA-5 positive group has been associated with rapidly progressive interstitial lung disease (RP-ILD) that is often aggressive and fatal. Several methods have been proposed to identify patients at increased risk for poor prognosis, but there is currently no consensus on testing or treatment.
Description: A 55-year-old Spanish speaking female presented to the ED with one month of progressive muscle aches, paresthesia, oral ulcers, and rash. Initial investigation revealed a significant transaminitis and a mildly elevated CK. She was admitted to the hospital and subsequent testing revealed a positive ANA and low C3 levels. Serum ferritin was elevated to >3000. She was started on high-dose corticosteroids with significant improvement in her symptoms, and she was discharged in stable condition. Further outpatient evaluation revealed positive anti-MDA-5 antibodies. Several weeks after discharge she presented with increasing shortness of breath and was found to be hypoxic and hypotensive. She was intubated and admitted to the ICU. She was initially started on IVIG and IV corticosteroids. Rituximab was added as an adjunct as she failed to improve. Despite aggressive intervention, her pulmonary function continued to deteriorate, and she was placed on comfort cares. From onset of her initial symptoms to her time of death was approximately 6 weeks.
Discussion: Elevated ferritin ( >500-1200) and anti-MDA-5 antibody levels have been proposed as surrogate markers for disease severity and risk of developing RP-ILD. However, current practice has relied on presence or absence of MSAs instead of measuring levels to guide treatment. Once present, survival rates in RP-ILD are extremely low so timely identification and initiation of therapy is vital. Existing research suggests that a combination of corticosteroids with another immunosuppressant should be implemented early in these patients. In this case, there was a failure to identify risk factors and initiate treatment which could have altered the disease course.