BONE HEALTH IN NMDS

Joyce and colleagues (234) have reviewed the recent literature regarding bone health as it relates to the patient living with NMD. Poor bone health is common in patients with NMD and is the cause of significant morbidity, including increased fracture rates and severe scoliosis. Bone health depends on a complex interplay of both local and distant mechanisms, including genetic, endocrine, neurologic, and lifestyle factors. Osteoporosis in NMD may be due to disease-specific pathophysiology, but appears to frequently be complicated by hypovitaminosis D with osteomalacia, as evidenced by incomplete improvements in bone density when serum vitamin D is replete. The use of glucocorticoids in DMD extends independent ambulation; however, its effects on bone health have not been completely studied, and may have adverse effects on bone density and increase fracture risk. Further studies are warranted. Further research is needed to assess the extent of poor bone health across all NMDs and to evaluate the efficacy of known osteoporosis treatments in this unique patient population with NMD.

MANAGEMENT OF CARDIAC COMPLICATIONS

Early treatment with ACE inhibitors is probably warranted in DMD when the measured ejection fraction falls below 55% (70,71). The benefits of earlier protective treatment with either ACE inhibitors or ARBs are under investigation. Digitalis has been demonstrated to be effective in decreasing morbidity from heart failure, but not mortality, and probably is also indicated for the treatment of heart failure observed in DMD patients with cardiomyopathy. Beta-blockers may also have a role in DMD. Treatment with coenzyme Q10 remains controversial. Cor pulmonale, confirmed on echocardiography, may benefit from continuous supplemental oxygen. Patients with known arrhythmias who are at risk for fatal tachyarrhythmias may benefit from anti-arrhythmic medication. DMD patients with mitral valve prolapse and mitral regurgitation should be given antibiotic prophylaxis for dental and surgical procedures in accordance with current guidelines.

The management of cardiomyopathy, seen in BMD, is similar to that seen in DMD; however, in cases of severe end-stage cardiomyopathy, cardiac transplantation should be considered.

Cardiac conduction abnormalities observed in myotonic muscular dystrophy may ultimately require implantation of cardiac pacemakers. In rare instances with cardiomyopathy, treatment may consist of ACE inhibitors, digitalis, and diuretics, based on proven efficacy in cardiomyopathies of other etiologies.

EMD patients with symptomatic bradycardia or heart block should undergo implantation of a permanent cardiac pacemaker. Atrial stand-still, atrial fibrillation, and atrial flutter are all disorders in which blood can pool in the atria, leading to thrombus formation and possible embolic events, including stroke. Anticoagulation with warfarin to an international normalized ratio (INR) of 2 to 3 has demonstrated a reduction in the incidence of stroke in patients with atrial fibrillation. Prompt referral to a cardiologist should be made for children with cardiac signs on symptoms or screening ECG, echocardiography, or for those with Holter recording abnormalities suggestive of cardiac disease. Late-stage DMD, BMD, and EMD patients should be followed by a cardiologist on a regular basis. There are selected subtypes of LGMD with cardiomyopathy warranting close follow-up and aggressive management. Appropriate management of cardiac complications in childhood NMD will likely lead to increased life expectancy and quality of life.

 
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