Abstract
Objective Carnitine is necessary for β-oxidation of fatty acids within the mitochondria. Carnitine deficiency often affects the skeletal and cardiac muscle. Secondary carnitine deficiency in adults can result from inadequate dietary intake, poor absorption, renal tubular dysfunction or medication side effects. Here we report a 72 year-old woman who presented with proximal lower limb weakness secondary to carnitine deficiency.
Case A 72 year-old woman presented with worsening mobility with increasing falls. She had a history of sensorineural hearing loss, chronic hydrocephalus and epilepsy on a background of childhood meningitis. She was on long-term phenytoin, primidone and sulthiamine. She had a normal diet and no significant family history. Examination revealed a symmetrical proximal lower limb myopathy. Magnetic resonance imaging (MRI) of the neural axis was non contributary, nerve conduction studies were unremarkable but electromyography was consistent with a myopathic process. MRI of the thighs showed patchy low-grade oedema suggestive of a myositis but her serum myositis autoantibody panel was negative and her serum creatinine kinase levels were normal. A muscle biopsy revealed multiple small and large vacuoles within myofibres on hematoxylin/eosin staining, which on oil red O staining were seen to contain lipid, consistent with a carnitine deficient myopathy. A serum acylcarnitine panel was consistent with secondary carnitine deficiency. The patient has made a dramatic improvement following oral carnitine replacement and adjustment of her antiepileptic medications.
Conclusion When identified, carnitine deficient myopathy is an easily treatable condition in which symptoms are largely reversible.
