Review Question - QID 105037

This patient initially received corticosteroid therapy for management of giant cell (temporal) arteritis. Her subsequent presentation of worsening proximal muscle weakness is consistent with corticosteroid-induced myopathy.

Steroid-induced myopathy is thought to occur more frequently with fluorinated steroids, such as dexamethasone or triamcinolone, over nonfluorinated agents such as prednisone or hydrocortisone. Reducing or discontinuing the dose of steroids will lead to spontaneous recovery; however, this may take weeks to months. In patients suffering from polymylagia rheumatica (PMR) being treated with steroids, it may be difficult to differentiate between recurrence of the disease (and need for an increased dose of steroids) versus development of steroid-induced myopathy (and need for a reduction in steroid dose). The critical difference is that steroid-induced myopathy, unlike PMR or inflammatory myositis, is associated with normal ESR and CK respectively.

Unwin et al. discuss the management of polymyalgia rheumatica and giant cell arteritis, focusing on the complications that may develop either from the disease itself or from chronic steroid therapy. Corticosteroid myopathy commonly presents with falls and/or weakness in rising from a chair. The only known effective therapy to improve the myopathy is reduction in the steroid dose. Additional precautions should also be taken in these patients, including fall prevention, physical therapy, and ambulatory assistive devices.

Kohsaka discusses steroid-induced myopathy. The pathogenesis of this condition is steroid-mediated induction and suppression of key enzymes, leading to an imbalance between the anabolism and catabolism of muscle proteins, manifesting as muscle atrophy. The diagnosis is difficult because it is not associated with significant alterations in any muscle enzymes, such as creatine kinase, LDH, or aldolase, and is therefore usually based primarily on patient history.

Illustration A summarizes the numerous side effects associated with chronic topical or systemic steroid therapy. Illustration B shows the histology of steroid-induced myopathy (right pane); note the black type 2 muscle fibers are significantly atrophied compared to a normal muscle section (left pane).

Incorrect Answers:
Answer 1: Mononeuritis multiplex is commonly coincident with arteritis; it is a painful and asymmetrical peripheral neuropathy leading to nerve damage in 2 separate areas of the body. Focal neurologic deficits are often noted, such as foot drop and sensory disturbances.
Answer 2: Polymyalgia rheumatica (PMR) presents with pain, stiffness, and weakness in the neck, pelvic girdle, and shoulder girdle. Although PMR and temporal arteritis commonly occur together, this patient's normal ESR and worsening symptoms on steroid therapy make PMR a less likely diagnosis. Additionally, pain is a more predominant symptom in PMR, whereas myopathy is more characterized by weakness.
Answers 4,5: Inflammatory myositis, including polymyositis and dermatomyositis, would be expected to present with an elevation in creatine kinase.