Physician Assistant Exam: The Polys and Proximal Muscles
With rheumatologic conditions, Physician Assistant Exam (PANCE) questions focus on discerning one proximal muscle condition from another. Two conditions that sound somewhat similar are polymyositis and polymyalgia rheumatica (PMR). Although both can affect the proximal muscles and have somewhat similar presentations, there are important differences between the two conditions.
Polymyositis is muscle damage caused by an overexcited immune system. The muscle damage is significant enough that you can see elevated creatine phosphokinase (CPK) levels, usually in the thousands; this condition is called rhabdomyolysis. The main presenting symptom of polymyositis is weakness that gets worse throughout the day.
Patients with polymyositis or any form of muscle weakness can have difficulty using their muscles when switching body positions. At its extreme, patients with any form of proximal muscle weakness may demonstrate a positive Gower’s sign, which means using the upper extremities to shift body positions. This is not specific to polymyositis — you see Gower’s sign from other causes as well.
The treatment for polymositis is immunosuppressive therapy, including steroids or other immunosuppressive medications. Exercise is crucial for maintaining strength and flexibility.
Polymyalgia rheumatica (PMR) is an inflammatory condition that, like polymyositis, affects the proximal muscles. Unlike polymyositis, the presenting complaint with polymyalgia rheumatica is pain and difficulty with range of motion, particularly in the shoulder area. The patient may have type B constitutional symptoms as well, including fever, chills, weight loss, and drenching night sweats.
With polymyalgia rheumatica, the lab assessment can show an elevated sed rate and elevated white cell and platelet counts. Anemia due to inflammation can be present as well.
The treatment for polymyalgia rheumatica is steroids. Serial sed rates are followed to monitor response to therapy, and the steroid dose is tapered accordingly.
The sed rate is also important when you’re comparing and contrasting polymyalgia rheumatica with fibromyalgia. Both can present similarly, with similar pain patterns, but polymyalgia rheumatica has an elevated sed rate, whereas fibromyalgia doesn’t.
Which one of the following medical conditions is associated with polymyalgia rheumatica?
(C) Systemic lupus erythematosus
(D) Temporal arteritis
(E) Rheumatoid arthritis
The answer is Choice (D). Polymyalgia rheumatica and temporal arteritis are connected. Temporal arteritis is associated with a headache and tenderness on the temporal artery. There can be ocular involvement, with eye pain and change in vision. The standard for the diagnosis of temporal arteritis is a temporal artery biopsy, although the biopsy is at risk of a sampling error and may not pick up the exact area of inflammation.
When the eye is affected, that’s an emergency, and a sed rate is ordered. If the sed rate is high, the patient is started on steroids. Isn’t this similar to the treatment of polymyalgia rheumatica?