Lipid Storage Disorder

Clinical History:

Demographics: 50-year-old woman

Chief complaint: Progressive generalized weakness for 6 weeks starting distally in hands and feet and progressed to the point where she was unable to stand or hold her head up and unable to feed herself and is associated with diffuse muscle pain and dysphagia.

PMH: Pseudotumor cerebri status post ventriculoperitoneal shunt and migraines

Medications: topiramate, tizanidine and cetirizine.

Physical exam: decreased tone and diffuse muscle atrophy; severe proximal > distal weakness and including neck flexion/extension and 0/5 bilateral foot dorsiflexion; reflexes: trace diffusely; sensation: intact.

Labs: CK elevated, lactic acid elevated; autoimmune myositis panel negative

The findings on Oil-red-O staining is most compatible with:

A. Mitochondrial dysfunction

B. Abnormal lipid storage

C. Secondary glycogen storage abnormality

D. Statin toxicity

Answer:

Lipid storage disorder

Pathological diagnosis:

• Increased lipid storage; suspicious for lipid storage myopathy
• Rare necrotic fibers
• Type II atrophy, mild

Abnormalities of lipid storage can occur as a secondary phenomenon in the setting of statin-induced myopathy/immune mediate necrotizing myopathy and/or rhabdomyolysis or primary lipid storage myopathy (LSM). [1,2] LSM generally occurs in three settings: 1) primary or secondary carnitine deficiency; 2) mitochondria disorders; and 3) genetic defects of lipid metabolism (including multiple acyl-coA dehydrogenase deficiency, responsive to riboflavin).[1] Serology for HMGCR antibodies, genetic testing, and/or metabolic testing may be useful in determining underlying etiology (reviewed in [3-5]).

Reference(s) / Additional Reading:

• Camerino GM. Int J Mol Sci. 2021;22:2070.
• https://neuromuscular.wustl.edu/pathol/statin.html
• Pennisi EM. J Clin Med. 2018 Nov 23;7(12):472.
• Berardo A. Curr Neurol Neurosci Rep. 2010 Mar;10(2):118-26.
• Angelini C. Ther Adv Neurol Disord. 2019 Apr 22;12:1756286419843359.