A 67-year-old man with lung cancer notices symptoms of weakness in his arms and legs. He describes difficulty in rising out of chair or going upstairs, but no pain or discomfort. On examination, proximal muscle strength is four out of five in the upper and lower limbs, but the reflexes, tone, and sensation are normal. He has a colored rash on his eyelids, and raised papules on his knuckles.For the above patient with muscle weakness, select the most likely anatomic site for the disorder
Dermatomyositis is one of the inflammatory myopathies that has a characteristic rash on the eyelids (heliotrope) and knuckles (Gottron's papules). It is associated with certain cancers as a paraneoplastic syndrome. The muscle enzyme creatine kinase (CK) is elevated is most cases, but the condition is painless. Symptoms are those of proximal muscle weakness, with normal reflexes and tone on examination.
anterior horn cell
peripheral nerve
neuromuscular junction
muscle
C.N.S.