Abstract
INTRODUCTION: Dermatomyositis (DM) is an idiopathic inflammatory myopathy characterised by skin involvement, with or without muscle disease. A known paraneoplastic entity, approximately one-third of DM cases are associated with malignancy, particularly within three years of diagnosis. Among the autoantibodies, anti-TIF1-γ is most strongly associated with cancer-associated DM. This case describes a middle-aged woman presenting with inflammatory myopathy and atypical ulcerative skin lesions, ultimately diagnosed as paraneoplastic DM linked to recurrent breast cancer. The case highlights an uncommon cutaneous presentation in a patient with a known cancer-associated myositis autoantibody, offering insight into diagnostic nuances and management challenges in paraneoplastic syndromes. CASE DESCRIPTION: A 42-year-old African female presented to the rheumatology outpatient clinic with a one-month history of difficulty standing from a squatting position and combing her hair. She had a prior history of hormone receptor–positive breast cancer, treated with lumpectomy eight months earlier in her home country. Clinical examination revealed symmetrical proximal muscle weakness (MMT-8 score: 117/150), Gottron’s papules, and calcinosis over the buttocks. Painful ulcerative skin lesions were noted, which are uncommon in TIF1-γ–associated DM. Cutaneous Dermatomyositis Severity Index (CDASI) scores were 19/100 (activity) and 2/32 (damage). Serum CPK was modestly elevated at 394 IU/L. The patient reported new-onset pain in the left axillary region, where lymphadenopathy was noted. PET-CT revealed multiple FDG-avid level I axillary lymph nodes and diffuse increased FDG uptake in skeletal muscles. Biopsy of the axillary nodes confirmed metastatic recurrence of invasive ductal carcinoma of the breast. Myositis line immunoassay (LIA) was positive for anti-TIF1-γ antibody. A diagnosis of paraneoplastic dermatomyositis associated with recurrent breast malignancy was established. She was initiated on systemic corticosteroids (oral prednisolone), topical corticosteroids, and sunscreen. Oncologists commenced adjuvant chemotherapy with doxorubicin and cyclophosphamide. She completed two cycles locally and opted to continue further treatment in her home country. DISCUSSION: This case illustrates the classical association of dermatomyositis with underlying malignancy, underscoring the diagnostic and management complexity in paraneoplastic presentations. TIF1-γ is one of the most common myositis-specific autoantibodies associated with cancer, particularly in adults over 40. Its presence warrants an extensive malignancy screen, even in patients with a known cancer history. Interestingly, our patient displayed ulcerative skin lesions—a feature more typical of anti-MDA5–associated DM. While ulceration is rarely associated with anti-TIF1-γ, it is still documented in the setting of paraneoplastic DM, reflecting a potentially overlapping phenotype or immune activation profile. The modest elevation of CPK despite significant muscle weakness and PET-CT muscle uptake emphasises the importance of correlating clinical, biochemical, and imaging data. While the standard treatment for idiopathic DM includes corticosteroids and immunosuppressants, in paraneoplastic DM, cancer control is central to managing myositis. Here, malignancy-targeted therapy was prioritised, alongside immunosuppression for symptom relief. This case raises important clinical questions: should skin ulceration in the context of TIF1-γ prompt clinicians to consider alternative or coexisting antibody profiles? How should treatment be tailored in patients with dual autoimmune and oncological pathology? Through this case, we advocate for vigilance in cancer surveillance in DM, especially in those with TIF1-γ antibodies, and for awareness of atypical cutaneous signs that may expand the known phenotype. KEY LEARNING POINTS: • TIF1-γ autoantibody is a key marker of cancer-associated dermatomyositis, especially in adults over 40. Its presence should prompt thorough malignancy screening, even in patients with a past history of cancer in remission. • Skin ulceration is uncommon but possible in anti-TIF1-γ–positive DM and should not exclude this diagnosis. It is more typically seen with anti-MDA5 but may also reflect severe immune activation in paraneoplastic contexts. • Clinical-imaging-biochemical discordance can occur, as seen with mildly elevated CPK despite significant clinical weakness and muscle FDG uptake on PET-CT. Comprehensive assessment is crucial. • Management of paraneoplastic DM focuses on malignancy control. Immunosuppression is supportive but less effective without oncological treatment. Early coordination with oncology is essential. • Case-based learning objectives for the conference: • To explore evolving phenotypes in antibody-associated myositis • To identify key features distinguishing idiopathic from paraneoplastic DM • To discuss practical approaches for malignancy screening and coordination between rheumatology and oncology • To reflect on treatment dilemmas in immunosuppression versus tumor-targeted therapy