Case Report: breast cancer presenting as dermatomyositis

Cancer-associated dermatomyositis (CADM) is a rare paraneoplastic syndrome characterized by inflammatory myopathy and distinctive cutaneous manifestations. Early recognition of an underlying malignancy is essential for improving patient outcomes.

We report the case of a 48-year-old woman who initially presented with dermatomyositis as the first manifestation of breast cancer. She was admitted with progressive dysphagia, violaceous edematous erythema involving the face and neck, and proximal muscle weakness of the extremities. The patient had previously been diagnosed with idiopathic dermatomyositis at another institution and treated with glucocorticoids; however, her symptoms showed no significant improvement. Further evaluation at our hospital revealed markedly elevated muscle enzyme levels. Autoantibody testing demonstrated weak positivity for anti-Jo-1 antibodies and positivity for anti-Ro-52 antibodies. Both skin and muscle biopsies supported the diagnosis of dermatomyositis. Comprehensive malignancy screening subsequently identified invasive carcinoma of the right breast with axillary lymph node metastasis. Following treatment with glucocorticoids combined with two cycles of neoadjuvant chemotherapy consisting of paclitaxel and platinum-based agents, the patient's skin lesions markedly regressed, muscle strength improved, and dysphagia was significantly alleviated. She subsequently underwent radical breast surgery followed by adjuvant radiotherapy, and her condition has remained stable during follow-up.

A review of the literature indicates that age >40 years, dysphagia, rapid disease progression, and positivity for anti-transcription intermediary factor 1-gamma anti-TIF1-γ antibodies are important risk factors for CADM. Thorough malignancy screening should be performed in all newly diagnosed patients with dermatomyositis, particularly for common associated malignancies such as breast cancer, lung cancer, ovarian cancer, and nasopharyngeal carcinoma. Clinicians should maintain a high index of suspicion for occult malignancy in patients who respond poorly to conventional dermatomyositis therapy. Early identification and effective treatment of the underlying malignancy are critical for improving the prognosis of CADM.