Transient elevation of the tumor markers CA 15-3 and CASA as markers of interstitial lung disease rather than underlying malignancy in dermatomyositis sine myositis

A 37-year-old woman with severe interstitial lung disease associated with dermatomyositis sine myositis is reported. A thoracoscopic lung biopsy revealed organizing diffuse alveolar damage. Significantly elevated serum levels of the tumor markers CA 15-3 and CASA (cancer-associated serum antigen) were detected, but no evidence of an underlying malignancy (including breast and ovarian) was found on serial clinical and radiologic examinations. These levels gradually normalized as the interstitial lung disease responded to a combination of cyclophosphamide and corticosteroids. The use of the CA 15-3 and CASA assays to measure serum levels of the highly glycosylated, high-molecular-weight mucin MUC1 in interstitial lung disease has not been previously described. Clinicians should therefore be aware that elevation of these tumor markers may reflect the presence of interstitial lung disease rather than an underlying malignancy in patients with dermatomyositis, especially if the levels normalize after successful treatment of the lung disease.