eMedicine Specialties > Physical Medicine and Rehabilitation > Myopathy

Corticosteroid-Induced Myopathy

Author: Steve S Lim, MD, Consulting Staff, Department of Physical Medicine and Rehabilitation, St Clare's Hospital of Dover
Coauthor(s): Patrick M Foye, MD, FAAPMR, FAAEM, Associate Professor of Physical Medicine and Rehabilitation, Co-Director of Musculoskeletal Fellowship, Co-Director of Back Pain Clinic, Director of Coccyx Pain Service (Tailbone Pain Service: www.TailboneDoctor.com), University of Medicine and Dentistry of New Jersey, New Jersey Medical School
Contributor Information and Disclosures

Updated: Sep 28, 2009

Introduction

Background

Steroid myopathy is usually an insidious disease process that causes weakness mainly to the proximal muscles of the upper and lower limbs and to the neck flexors. Cushing originally described it in 1932, and Muller and Kugelberg first studied it systemically in 1959. An excess of either endogenous or exogenous corticosteroids is believed to cause the condition. Excess endogenous corticosteroid production can arise from adrenal tumors. An excess of exogenous corticosteroid can result from steroid treatment for asthma, chronic obstructive pulmonary disease, and inflammatory processes, such as polymyositis, connective tissue disorders, and rheumatoid arthritis.^1,2,3

Pathophysiology

Steroid myopathy may be more frequent with the use of fluorinated steroids, such as dexamethasone⁴ or triamcinolone, than with nonfluorinated ones, such as prednisone or hydrocortisone.^5,6 Although the exact mechanism of the muscle pathology is unclear, it may be related to decreased protein synthesis, increased protein degradation, alterations in carbohydrate metabolism, mitochondrial alterations, electrolyte disturbances, and/or decreased sarcolemmal excitability. Sedentary lifestyle may increase the risk of muscle weakness in a patient taking corticosteroids, since corticosteroids seem to affect less active muscles preferentially. Two distinct types of steroid myopathy exist, acute and chronic. The chronic (or classic) form occurs after prolonged use of corticosteroids and has a more insidious course. The acute form is less common, is associated with rhabdomyolysis, and occurs abruptly while the patient is receiving high-dose corticosteroids.

Frequency

United States

The exact incidence of steroid myopathy is unknown; sensitivity to particular medications varies among patients.

Mortality/Morbidity

The weakness seen with steroid myopathy typically resolves after the corticosteroid dose is reduced or discontinued, although recovery can take weeks or months. Case studies have reported a lack of full recovery, as well as difficulty weaning patients off of mechanical ventilation. Osteoporosis, which can occur as a comorbidity with steroid myopathy, can result from the corticosteroid or from decreased mobility and respiratory impairment.⁷ Other comorbidities include joint contractures, pressure ulcers, and deep vein thrombi, although these can occur in any condition causing weakness and immobility. Mortality has not been described. Some case studies have reported patient mortalities, but they provided no indication that steroid myopathy was the cause.

Sex

For a given dose of steroid, women appear to be twice as likely as men to develop muscle weakness, although the reason is unclear.

Clinical

History

• Chronic (classic) steroid myopathy
  • This form is the classic presentation of steroid myopathy.
  • This condition can develop after prolonged administration of prednisone at a dose of 40-60 mg/d.^5,6 Although there is no clear length of time, onset of weakness has been found to occur within weeks to years following initiation of corticosteroid administration.
  • Several studies have suggested that the risk for steroid-induced myopathy is greater in severely asthmatic patients who use oral steroids.⁸ One study, however, found no significant difference in the prevalence of myopathy in oral steroid users and inhaled steroid users.
  • A report by Stanton et al indicated that in 43 patients with asthma, a statistically significant association existed between inhaled corticosteroid dose and patient voice scores obtained using the GRBAS (grade-roughness-breathiness-asthenicity-strain) system.⁹ Despite this apparent relationship, however, evidence of steroid-induced myopathy was found in only 2 of the 43 patients.
  • Fluorinated steroids seem to produce weakness and myopathy more frequently than do nonfluorinated ones.
  • The insidious onset of proximal muscle weakness of the upper and lower limbs is a prominent clinical feature.
  • Progressive proximal muscle weakness of the upper and lower limbs is reported.
  • Patients typically complain of a progressive inability to rise from chairs, climb stairs, and perform overhead activities.
  • Patients initially note little difficulty with hand strength.
  • The facial and sphincter muscles usually are spared.
  • Myalgias can become a prominent feature with time.
  • Contrary to previous beliefs, several studies have shown involvement of the respiratory muscles (eg, the diaphragm); thus, pulmonary symptoms may be present.⁷
• Acute steroid myopathy
  • This form is encountered less frequently than is the chronic type.
  • Acute, generalized weakness, including weakness of the respiratory muscles, typically occurs 5-7 days after the onset of treatment with high-dose corticosteroids.⁷ Some case reports describe the development of muscle weakness after the administration of a single dose of corticosteroid.
  • One study indicates a possible correlation between the occurrence of acute steroid myopathy and the total dose of steroid administered; acute atrophy was encountered with total doses of greater than 5.4 g of hydrocortisone in 6 days, whereas no signs of myopathy were noted with total doses of less than 4 g.
  • Previous systemic corticosteroid use does not appear to contribute to the development of myopathy.

Physical

• Chronic (classic) steroid myopathy
  • Proximal muscle weakness is more pronounced than is distal muscle weakness; however, severe relative weakness of the anterior tibialis muscle can be found.
  • Pelvic girdle muscles usually are affected more severely and earlier than are pectoral girdle muscles.
  • Muscle bulk typically is normal, but muscle atrophy can occur.
  • Muscle stretch reflexes typically are normal.
  • Sensory examination should be normal.
• Acute steroid myopathy
  • Generalized muscle weakness, not limited to a more proximal distribution, is noted.
  • Muscle stretch reflexes typically are normal.
  • Sensory examination should be normal.

• Search for CME/CE on This Topic »