Objective:

This review describes the clinical, laboratory, and electrodiagnostic characteristics of a cohort of patients with anti-Ku myositis.  

Background:

Inflammatory myopathies are a heterogeneous group of autoimmune diseases.¹ Autoantibodies predict associated systemic involvement and response to treatment. Anti-Ku myositis has a unique phenotype presenting with distal weakness, respiratory, skin, and gastrointestinal involvement^1–3.  It is responsive to steroids and carries a favorable prognosis⁴.

Design/Methods:

We tested the sera of patients presenting with systemic connective tissue disorders and symmetric muscle weakness with the myositis antibody panel through Washington University Neuromuscular Clinical Laboratory. Demographic, clinical, laboratory, and treatment data were obtained from medical records. 

Results:

All sera were positive for anti-Ku by Western Blot. Two patients concurrently tested positive for Anti-RO 52, one patient tested positive for anti-MDA5, PMSCL 125, and anti-OJ, in addition to borderline Anti-Ku. Mean age 57.5 years. There were two males and two females. Serum creatine kinase (CK) was elevated in all four (mean value 1367U/L, range 372-1556U/L), with the lowest CK in the patient positive for four other antibodies. No malignancy was identified in any patient. Two patients experienced proximal muscle pain, one patient had unilateral limb swelling, two patients had an erythematous rash on the extensor surfaces of the hands, one patient exhibited esophageal dysmotility. Muscle biopsy was obtained in three patients, was normal in one, and showed evidence of inflammatory myopathy in the others. Nerve conduction (NCS) and electromyography (EMG) were obtained which demonstrated evidence of a chronic myopathic process with evidence of muscle membrane irritability. Two patients were treated with both IVIg and oral prednisone (10-20mg once a day) and demonstrated mild improvement in MRC grading of muscle strength.

 

  

Conclusions: