Primary idiopathic polymyositis does not involve –
**Core Concept**
Primary idiopathic polymyositis is an autoimmune inflammatory muscle disease characterized by progressive muscle weakness and wasting, primarily affecting the proximal muscles. It is a type of inflammatory myopathy that involves the skeletal muscles and is often associated with the presence of autoantibodies.
**Why the Correct Answer is Right**
Primary idiopathic polymyositis is a muscular disease, not a neurogenic or neuromuscular junction disorder. The pathophysiology involves the activation of immune cells, such as T cells and macrophages, which cause muscle damage and inflammation. The disease is often associated with the presence of autoantibodies against muscle proteins, including the anti-Jo-1 antibody.
**Why Each Wrong Option is Incorrect**
**Option A:** This option may be incorrect, as polymyositis can occasionally involve the muscles of the tongue or extraocular muscles, but this is not a characteristic feature of the disease.
**Option B:** This option may be incorrect, as polymyositis can involve the muscles of the face or neck, but this is not a distinguishing feature of the disease.
**Option C:** This option is incorrect, as polymyositis is a disease of the skeletal muscles, not the peripheral nerves.
**Clinical Pearl / High-Yield Fact**
The presence of muscle enzymes, such as creatine kinase (CK), in the serum is a hallmark of polymyositis and can be used to diagnose the disease.
**Correct Answer: C. Peripheral nerves**