Paraneoplastic Dermatomyositis Preceding Gastroesophageal Junction Adenocarcinoma: A Case Emphasizing the Importance of Early Malignancy Screening

Dermatomyositis (DM) is an idiopathic inflammatory myopathy marked by proximal muscle weakness and pathognomonic rashes such as heliotrope rash and Gottron papules. DM is associated with an increased risk of malignancy compared to the general population, with 15-30% of cases being paraneoplastic. DM-associated malignancies are often diagnosed at late stages, resulting in cancer being a leading cause of death in this condition. Additionally, DM can mask malignancy by presenting with similar symptoms as the inciting cancer, further emphasizing the importance of early, disease-specific cancer screening. We report a 51-year-old woman with refractory DM presenting with muscle weakness, cutaneous lesions, and dysphagia. Lab tests showed elevated creatine kinase, positive ANA, and negative anti-Jo-1; muscle biopsy confirmed DM. Despite treatment for DM, her symptoms persisted. After complaints of worsening dysphagia, subsequent imaging, endoscopy, and biopsy revealed gastroesophageal junction (GEJ) adenocarcinoma. After receiving immunosuppressive treatment, the patient developed Pseudomonas pneumonia. Unable to recover, she rapidly declined and died in mid-April 2025. This case emphasizes the need for early myositis-specific malignancy screening in new-onset DM, particularly when systemic or gastrointestinal symptoms are present. This will enable timely diagnosis and improve patient outcomes. Paraneoplastic DM often carries a more aggressive course, and while gastrointestinal (GI) cancers are highly associated with the disease, association with GEJ adenocarcinoma is rare. A high index of suspicion for malignancy should be maintained in new-onset DM, especially when systemic symptoms are present. Early malignancy screening tailored to myositis-associated malignancies at the time of diagnosis is critical to improve prognosis and facilitate timely intervention in this life-threatening paraneoplastic syndrome.