Inflammatory myopathies are a group of inflammatory disorders involving the skeletal muscles and include dermatomyositis, polymyositis and inclusion body myositis. Dermatomyositis affects the skin and characteristic findings include Gottron's papules, per orbital oedema and heliotrope rash of the eyelids. It has a well-known association with malignant tumours, in particular lung, breast, ovary and gastrointestinal tumours and non-Hodgkin lymphoma. The occult neoplasm is usually detected 2 years after the onset of myositis.4
However, in our patient, the gastric tumour was detected only a few days after he had been evaluated for myositis. Unusually, he had no gastrointestinal related symptoms and the inflammatory myopathy was the first clinical manifestation of an occult poorly differentiated gastric carcinoma.
Myositis associated with malignancy behaves differently from idiopathic disease and may be resistant to immunosuppressive drugs. As a result, tumour resection and targeted cancer therapy are sometimes the only effective measures. Response depends on whether the myositis runs its course as a paraneoplastic disorder or progresses as an independent disease. In our case, our patient's symptoms responded significantly to prednisolone 1 mg/kg. It is not uncommon for an idiopathic inflammatory myopathy to recur after a lengthy quiescent period, an inherent feature of autoimmune disorders. However, myositis flare-up in a known cancer patient might herald tumour relapse.5–9
There are also recent reports of prostate cancer, bladder cancer and testicular tumours in association with myositis, so the role of increased physician awareness and improved diagnostic modalities cannot be overemphasised.10–12
As the underlying malignancy determines prognosis and influences treatment, it is strongly recommended that patients with inflammatory myopathy are investigated for an occult neoplasm; the value of cancer antigens such as 19-9 is still in doubt.3 13
In conclusion, we believe this report may help to remind us to screen our patients thoroughly for underlying disease before diagnosing an idiopathic disorder.
- Uncommon presentation of gastric cancer should be considered.
- An occult neoplasm should be considered in a patient presenting with myositis.
- The patient's clinical findings should be evaluated as a whole.