A Case of a 50-Year-Old Female with Dermatomyositis Secondary to a Paraneoplasm (Infiltrating Ductal Carcinoma, Grade 2)

Introduction: Dermatomyositis is an autoimmune disorder with an incidence of 5 to 10 per 1 million per year. 10 to 20% of patients with adult-onset Dermatomyositis have an underlying malignancy. There are currently no specific cutaneous markers for Paraneoplastic Dermatomyositis. This case highlights a patient with uncommon features of paraneoplasm after breast malignancy. Case Report: A 50-year-old female with Infiltrating Ductal Carcinoma, presented with patches on the face, neck, chest, upper back, outer arms, dorsal hands, thighs, hair loss and weakness. Histopathology revealed widened basal layer vacuolization with widened spaces between collagen bundles filled with mucin deposition, and pigment incontinence in the papillary dermis. Direct immunofluorescence showed granular deposits of IgG, C3, IgM and IgA in the basement membrane zone, which are consistent with Dermatomyositis. The patient was prescribed with Clobetasol ointment mixed equally with petrolatum on the body and Mometasone cream on the face. She was subsequently started on Prednisone at 0.5 mkd with eventual tapering, Omeprazole, and Calcium + Vitamin D tablet daily. Hydroxychloroquine 200 mg/tab daily was added. Referral to Rheumatology for co-management and Surgery for management of the breast mass was also done. Conclusion: This case emphasizes the rare occurrence of a Paraneoplastic Dermatomyositis following a diagnosis of breast malignancy. A careful review upon diagnosis may detect occult malignancies especially in patients who present primarily with cutaneous Dermatomyositis. Clinicopathologic correlation and a multi-disciplinary approach, with Surgery, Oncology, Rheumatology and Dermatopathology are needed to identify the underlying cause and facilitate successful treatment of a neoplasm followed by improvement of Dermatomyositis.