Unilateral Lower Limb Focal Myositis

Focal myositis is a rare inflammatory myopathy characterised by a localised swelling of skeletal muscle that is usually located in the lower extremities. It can be readily confused with tumours or other inflammatory diseases and around one hundred cases are described in the global literature.

Focal myositis presents as a mass localised to a single skeletal muscle that may be painless or tender to the touch and that appears after growing insidiously over several weeks to months. The mass is usually located in the lower extremities and the muscles most commonly affected include the adductor, vastus lateralis and gastrocnemius. It can rarely occur in muscles of the head and neck region.

We report a case of a 60 year old, female patient who developed swelling in calf muscle without the history of trauma. She came with a painful swelling appearing on the right lower limb, growing progressively in the last 10 days, followed by a spontaneous moderate local pain, getting worse on movement. MRI showed a diffuse high signal intensity in the right gastrocnemius muscle, images revealed oedematous changes in adjacent soft tissues and signs corresponding to myositis. The collective findings were consistent with a diagnosis of focal myositis. Appropriately, non-steroidal anti-inflammatory therapy with physical therapy was performed. A physical examination performed 14 days after initiation of the treatment, revealed improvement in tenderness and pain.