Colon cancer presenting with polymyositis-A case report

Colorectal cancer most often presents with a change in bowel habit, weight loss or with bleeding per rectum. Much less commonly, colorectal cancer may present as part of a paraneoplastic syndrome. Polymyositis is a rare disease most often considered a complement-mediated idiopathic inflammatory myopathy manifested by proximal muscle weakness. However, polymyositis may also be part of a paraneoplastic syndrome associated with an underlying malignancy. The relationship between polymyositis and malignancy is well known, but it has been suggested that tumours of the large bowel are rarely complicated by myositis.

The authors describe a case report of an 82-year-old gentleman with a presumed musculoskeletal or neurological deficit who was subsequently diagnosed with metastatic colon cancer in the setting of progressive fatigue and muscle weakness. Concurrently, we review the current literature looking at the relationship between cancer and polymyositis.

Colorectal cancer rarely presents with symptoms such as muscle weakness, however it is important to be aware of the possibility of an underlying malignancy when seeing patients with symptoms which are suggestive of polymyositis.

The diagnosis of polymyositis in the elderly population should raise suspicion of an underlying malignancy.