Clinical History:
The patient is a 77-year-old female with several months of progressive muscle weakness predominantly in her upper and lower proximal extremities. Medications include levothyroxine and atorvastatin. Lab results include a reportedly low CK, aldolase 92 U/L, negative myositis autoantibody panel, negative HMGCR autoantibody testing.
What treatment should be given immediately?
A. Riboflavin
B. Immediately discontinue atorvastatin
C. Highly Active Antiretroviral Therapy
D. High-fat diet
Answer:
A. Riboflavin
The clinical history and images are concerning for a lipid storage myopathy. The differential includes genetic defects in components of the lipid metabolism pathway, mitochondrial disorders, and carnitine deficiency. Lipid metabolism pathway defects include neutral lipid storage disease of muscle (NLSD-M) caused be PNLA2 mutations, carnitine palmitoyltransferase 2 (CPT2) deficiency, riboflavin responsive multiple Acyl-CoA dehydrogenase deficiency (rr-MADD) caused by ETFDH mutations, and muscle carnitine deficiency primarily due to mutations in the SLC22A5 gene. Late onset riboflavin responsive MADD patients may manifest proximal myopathy, high CPK levels, vomiting and hypoglycemia, and typically respond well to riboflavin with carnitine supplementation.
Discontinuing atorvastatin would be useful in the setting of a necrotizing myopathy.
HAART is associated with mitochondrial abnormalities due to zidovudine inhibiting mitochondrial DNA polymerase-ƴ. But HIV infection is not associated with lipid storage myopathy.
A low fat diet can be helpful in lipid storage myopathies not a high-fat diet.
Reference(s) / Additional Reading:
- Camerino GM, Tarantino N, Canfora I, De Bellis M, Musumeci O, Pierno S. Statin-induced myopathy: translational studies from preclinical to clinical evidence. Int J Mol Sci. 2021;22(4):2070.
- Pennisi EM, Garibaldi M, Antonini G. Lipid myopathies. J Clin Med. 2018;7(12):472.
- Berardo A, DiMauro S, Hirano M. A diagnostic algorithm for metabolic myopathies. Curr Neurol Neurosci Rep. 2010;10(2):118-126.
- Angelini C, Pennisi E, Missaglia S, Tavian D. Metabolic lipid muscle disorders: biomarkers and treatment. Ther Adv Neurol Disord. 2019;12:1756286419843359.
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