Myopathy secondary to intravascular large B-cell lymphoma

Abstract We report a case of a 78-year-old woman presenting with progressive proximal muscle weakness mainly to lower limbs and myopathic EMG associated with intravascular large B-cell lymphoma. Muscle biopsy showed myopathic changes, intravascular large B-cell lymphoma but no inflammation or fibre necrosis; the patient’s serum cross-reacted with an unidentified nuclear antigen of approximately 45 kDa present in muscle and lymphoma cells. Our case illustrates a myopathy associated with intravascular large B-cell lymphoma probably mediated by antibodies cross-reacting with a nuclear protein expressed by neoplastic cells and normal muscle. The nature of this nuclear antigen remains unidentified.