Anti-PM/Scl-Positive Antibody with Dermatomyositis-Associated Interstitial Lung Disease: a Case Report

The objective of this case is to report on dermatomyositis-associated interstitial lung disease, and a rarely encountered antibody, anti-PM/Scl. We present clinical context, laboratory findings, and treatment related to this case, as well as, review of relevant literature. A 45-year-old female with a past medical history of hypertension who was being treated for suspected psoriasis was referred to out-patient rheumatology after being found to be strongly positive for antinuclear antibody and noted to have clubbing of her fingers. The patient reported some soreness of her proximal and distal interphalangeal joints with difficulty moving her fingers and mild dyspnea when climbing stairs. The patient had imaging and testing suggestive of interstitial lung disease, and lab work significant for normal creatinine phosphokinase and serology revealing elevated rheumatoid factor with myositis panel significant for positive anti-PM/Scl 70 antibody at 100 units, and further antibody testing negative for RNA polymerase 3, anti-cyclic citrullinated peptide, anti-RNP, anti-Sm, anti-SS-A (Ro), anti-SS-B (La), anti-Jo-1, anti-TIF1, Mi2, NXPs, SAE, and MDA5. The patient underwent a skin biopsy that was positive for interface dermatitis, consistent with dermatomyositis. The patient was started on mycophenolate mofetil with improvement in her rash and dyspnea. This case report reviews a common manifestation of dermatomyositis, interstitial lung disease, and the importance of screening dermatomyositis for the presence of interstitial lung disease. It also reviews the significance of a rarely encountered antibody, anti-PM/Scl. Dermatomyositis and polymyositis carry an increased risk of various malignancies; however, interestingly, a meta-analysis found that the presence of the anti-PM/Scl antibody was associated with the absence of cancer.