Myasthenia Gravis, Steroids, and Osteoporosis Prevention

Abstract & Commentary

Source: Lewis SJ, Smith PE. Acta Neurol Scand. 2001;103: 320-322.

Guidelines for osteoporosis prevention during long-term steroid use often go unheeded. Two recommendations are offered: 1) bone density measurements using dual energy X-ray absorptiometry (DEXA) scanning every 1-3 years for patients on > 7.5 mg/d prednisolone for > 6 months; and 2) bisphosphonate treatment for patients on > 15 mg/d prednisolone (prednisolone is dose equivalent to prednisone) for > 6 months, regardless of DEXA result (Eastell R, et al. J Intern Med. 1998;244:271-292). Patients older than age 65, or demonstrating abnormal DEXA, existing osteoporotic fractures, premature menopause, or slender build, are also advised to take bisphosphonate. Remarkably, few neurologists appear to follow these suggestions.

Among 80 confirmed myasthenia gravis (MG) patients (47 male, mean age 63.3 years), followed by 5 consultant neurologists in a catchment area of 1.2 million, 34 (42.5%) were on corticosteroids for MG, all for longer than 6 months. Of these, 16 (47%) were on < 7.5 mg/d and 18 on > 7.5 mg/d. Only 4 patients from each group had undergone DEXA scanning (22% of those indicated). Of the 18 taking > 7.5 mg/d, 13 fulfilled bisphosphonate-recommended criteria but only 7 (54%) were so prescribed. Two each of the remaining 6 were taking calcium supplements, vitamin D, or no prophylaxis.

Neurologists prescribe steroid medication for MG moreso than for any other indication and should be attentive to osteoporosis prevention.

Commentary

Osteoporotic fracture risk is best predicted by bone mineral density measurements. Each standard deviation of reduction in bone density augurs a > 2-fold increase in fracture (Marshall D, et al. BMJ. 1996;312: 1254-1259). For fracture prevention, hormone replacement—the gold standard for women—or bisphosphonates are indicated. Bisphosphonates, including alendronate (Fosamax) and risedronate (Actonel), block osteoclastic bone resorption, directly inhibit calcium-phosphate crystallization, and increase bone mass. Alendronate has been shown to reduce hip fractures by 50% and reduce hospitalizations and the need for prolonged bed rest due to back pain. Neurologists are in an ideal position to ensure that MG patients are given the full benefit of osteoporosis prophylaxis. —Michael Rubin