Abstract
Disorders of lipid metabolism affect several tissues, including skeletal and cardiac muscle tissues. Lipid myopathies (LM) are rare multi-systemic diseases, which most often are due to genetic defects. Clinically, LM can have acute or chronic clinical presentation. Disease onset can occur in all ages, from early stages of life to late-adult onset, showing with a wide spectrum of clinical symptoms. Muscular involvement can be fluctuant or stable and can manifest as fatigue, exercise intolerance and muscular weakness. Muscular atrophy is rarely present. Acute muscular exacerbations, resulting in rhabdomyolysis crisis are triggered by several factors. Several classifications of lipid myopathies have been proposed, based on clinical involvement, biochemical defect or histopathological findings. Herein, we propose a full revision of all the main clinical entities of lipid metabolism disorders with a muscle involvement, also including some those disorders of fatty acid oxidation (FAO) with muscular symptoms not included among previous lipid myopathies classifications.
Highlights
Lipid myopathies (LM) are a group of muscular diseases with onset in all ages, due in most cases to enzymatic errors of lipid metabolism
Primary Carnitine Deficiency (PCD) could manifest with a wide spectrum of clinical symptoms, ranging from asymptomatic patients, episodic exertional rhabdomyolysis, hypertrophic or dilated early onset cardiomyopathy, generalized muscle weakness, to severe infantile Reye-like syndrome mainly characterized by recurrent hypoglycemic hypoketotic encephalopathy
As in Very-Long-Chain acyl-CoA Dehydrogenase Deficiency (VLCADD), Long-Chain 3-hydroxyacyl-CoA Dehydrogenase Deficiency (LCHADD), Multiple Acyl-CoA Dehydrogenase Deficiency (MADD), or Carnitine- Acylcarnitine Translocase (CACT) deficiency, in CPT2 deficiency urgent treatment should be meticulous as there is a high risk of serious complications
Summary
Lipid myopathies (LM) are a group of muscular diseases with onset in all ages, due in most cases to enzymatic errors of lipid metabolism. The FA are metabolized in mitochondria by Electron-Transfer Flavoprotein (ETF) and beta-oxidation enzymes Any change in these different steps can cause a lipid myopathy which, to other metabolic myopathies, can be clinically characterized by exercise intolerance with fluctuant or fixed weakness, rhabdomyolysis and myoglobinuria (red brown colored urine), myalgias, eventually associated to muscle atrophy and involvement of other organs (liver, heart and central nervous system). PM: plasma membrane; LM: lipid myopathy; C: cardiomyopathy; E: encephalopathy; Ex: excercise intolerance; D: dysmorphims; He: hepatopathy;; Hy: hypoglycemia; M: fixed myopathy; My: myalgia; MA: metabolic acidosis; N: neuropathy; NC: normal carnitine; NH: neonatal hypotonia; OA: organic aciduria; R rabdomyolisis; RL: Reye like syndrome; Ic: ichthiosis; IOL: internal organ lipidosis; TM: transient myopathy; AC: abnormal acylcarnitine; EL: elevated lactate; CK: creatine kinase elevation; JA: Jordans’ anomaly; LC: low carnitine; DBS: dried blood spot; MCT: medium chain triglycerides; CoQ: coenzyme Q; +++: abundant; +/−: mild or absent; NR: not reported
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