Cervicobrachial polymyositis.

OBJECTIVES: To characterize and analyze a subgroup of patients with polymyositis presented with predominant or isolated proximal upper limb and neck weakness.

METHODS: Patients with polymyositis, presenting with predominant or isolated weakness of upper limbs and the neck, were included. Bohan and Peter and Targoff criteria were used for the diagnosis of polymyositis. The study period was of 14 years (from 1999 to 2013). Detailed clinical, laboratory, histopathological, and/or radiological profiles were evaluated and analyzed in all patients.

RESULTS: The mean age of presentation was 37 years (23-58 years), and 86% (12/14) patients were female. All patients developed progressive symmetrical weakness predominantly affecting upper limbs, and 50% (7/14) had weakness only in upper limbs. The referring diagnoses in all 14 patients were other than polymyositis, for example, motor neuron disease, cervical radiculopathy, brachial neuritis, chronic inflammatory demyelinating polyradiculoneuropathy, anti-MuSK myasthenia gravis, and facioscapulohumeral muscular dystrophy. Weakness in the neck and shoulder region was the most common presenting complaints, presenting in 71.4% (10/14) and 64.3% (9/14) of patients, respectively, followed by neck and shoulder pain in 57.14% (8/14) patients. The most severely affected muscles were neck flexors, neck extensors, the trapezius, and the deltoid. Less severe but preferential involvement of wrist and finger extensors was present. Serum creatine kinase was elevated (median CK, 1275 IU/L). Of note, 42.8% (6/14) had associated systemic autoimmune antibodies such as ANA, RA, and anti-Ro antibodies, whereas 36% (5/14) patients had associated interstitial lung disease (ILD). Active irritative myopathy was found in 93% (13/14) patients on needle electromyography studies, and all patients had evidence of inflammatory myopathy (polymyositis) on muscle biopsy. MRI of the cervicobrachial region was performed in the first 6 patients showing T2 hyper intensities (6/6) and contrast enhancement (4/4) of clinically affected muscles. Eighty-six percent (12/14) of patients responded to corticosteroids with an average response initiation time of 7.4 weeks (1-12 weeks). Subsequently used steroid sparing agents were azathioprine (6/14) and methotrexate (6/14). Intravenous immunoglobulin (IVIG) was used in 2 patients and plasmapharesis in 1 patient.

CONCLUSIONS: Cervicobrachial polymyositis presents with predominant or isolated proximal upper limb and neck weakness. It has marked female preponderance and affects neck flexors and extensors and trapezius and deltoid muscles severely. Wrist and finger extensors are also weakened. In a proportion of patients, it is associated with serological markers of autoimmune disorders and interstitial lung disease. In addition to serum creatine kinase, electromyography, and muscle biopsy, magnetic resonance imaging forms a noninvasive adjunct test in the diagnostic process. Because of the pattern of weakness, cervicobrachial polymyositis tends to be confused with other common neurological conditions having upper girdle weakness, leading to delay in the diagnosis of this potentially treatable condition.