A 57-year-old female college counselor living in the northeastern United States with no PMH presented for evaluation of rash, joint pain, and dyspnea for the past three weeks. The patient first noticed the rash on her upper back, describing it as being itchy. The rash then spread to her face, scalp, and thighs. Two weeks ago, she noticed swelling in her hands and had a gradual onset of dyspnea on exertion. The patient has pain in her hands and when moving her fingers. She denied fever, cough, chills, chest pain, headache, vision changes, focal weakness, abdominal pain, nausea, vomiting, and diarrhea. She denied recent travel, sick contacts, significant time spent outdoors, known tick bites, new medications, and changes in her diet. She has never had a rash like this before.
Amyopathic dermatomyositis – specifically anti-melanoma differentiation-associated gene 5 (anti-MDA5) positive dermatomyositis as determined by subsequent inpatient auto-immunological workup. Compared to other dermatomyositides, anti-MDA5 positive dermatomyositis is characterized by an absence of traditional muscular involvement. Additionally, patients can present with respiratory symptoms related to interstitial lung disease (ILD). One phenotype of this condition is associated with a rapidly progressive ILD, but respiratory involvement may be delayed years after the initial symptoms are noticed. The patient’s clinical images demonstrate a macular, violaceous rash in the “shawl sign” and “holster sign” distribution patterns typical of dermatomyositides. Palmar papules (not to be confused with Gottron’s papules which are found on the dorsal surface of the metacarpophalangeal and interphalangeal joints) are fairly specific for anti-MDA5 positive dermatomyositis
There are no specific guidelines for treating anti-MDA5 positive dermatomyositis. Patients are typically started on a high-dose steroid regimen. A rheumatology consult should be obtained to determine if the patient would benefit from treatment with immunosuppressants. Given her complaints of dyspnea, the patient should undergo a non-contrast CT of the chest to evaluate for evidence of scarring or pulmonary fibrosis.
Anti-MDA5 positive dermatomyositis is associated with rapidly progressive ILD has a poor prognosis.
This rare form of dermatomyositis should be suspected if the patient has respiratory complaints in addition to the hallmark cutaneous findings commonly observed in all types of dermatomyositides. Palmar papules are fairly specific for anti-MDA5 positive dermatomyositis. It often lacks typical historical and physical features of muscular weakness.
Treatment involves high-dose corticosteroids and consideration of immunomodulator therapy.
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