Focal Myositis of the Sternocleidomastoid Muscle: A Rare and Uncommon Cause of Cervical Mass

We report on a 70-year-old male patient admitted to the internal medicine department for evaluation of a right cervical mass. He had been treated with antibiotics as an outpatient by his primary care doctor. Upon admission the patient was asymptomatic, but within a few hours his cervical mass enlarged; this enlargement was confined to the right sternocleidomastoid muscle. Complete blood investigations including serology and autoimmunity were negative. The neck scan and MRI were in favour of myositis. No other lesions were found either in the nasal fibre-optic exam or in the thoracic-abdominal-pelvic scan. The biopsy of the muscle showed a lymphoplasmacytic inflammatory infiltrate of the perimysium. The diagnosis of focal myositis was made. The patient clinically improved during hospitalisation with complete resolution of symptoms without any specific intervention. LEARNING POINTS: A thorough clinical examination is essential in the evaluation and characterisation of cervical masses. The diagnostic approach must be rigorous in order not to ignore potentially serious diseases. A high level of clinical suspicion is needed in the diagnosis of focal myositis.