Fatigue in muscular dystrophy and metabolic myopathy

Abstract

Muscular dystrophy is a heterogeneous group of disorders characterized by decreased muscle mass, atrophy and connective tissue proliferation. nNOS (nitric oxide synthase) is an important regulator of vascular blood flow. Metabolic myopathies mare disorders of utilization of carbohydrates and fatty acids in muscle. The acute nature of energy failure is manifested either by a metabolic crisis (CPT-II deficiency), muscle weakness sometimes associated with respiratroy failure (GSDII). The discovery of a new syndrome, NLSD-M (neutral lipid storage disorder), introduces the need of the response to therapy, either dietary or medical, to prevent for each disorder the chronic fatigue, the respiratory insufficiency and cardiomyopathy. Fatigue is a complex phenomenon related to exercise performance and muscle metabolism chosen as a primary endpoint in the overall glycogenosis cases. In other cases, critical events, such as myoglobinuria with increased serum creatine kinase is found. The impact of several polymorphisms reveals variants in the same genetic disorders. MicroRNAs regulate muscle mass and atrophy but their role in these disorders is under investigation. Current therapy consists in steroids for muscular dystrophies, carnitine, riboflavin, medium chain triglycerides, and enzyme replacement therapy for glycogenosis type II. The availability of new therapy can be life-saving for some of these disorders.