Lipid lowering drugs are used worldwide to control dyslipidemias. The muscle disorder associated with them are coined cholesterol-lowering agents myopathy (CLAM) 1 . The annual incidence of rhabdomyolysis in patients taking statins is 3.4 per 100000 persons 2 . Between 1987 and 2001 there were 42 deaths +related to statin-induced rhabdomyolysis, resulting in a mortality rate of 0.15 per million of prescriptions 3 . Although myotonic potentials have been described in some drug-related myopathies, they are rarely reported in CLAM. Though there are a few experimental myotonic myopathy associated with statin in rabbits 4-6 , there was only one single report describing 5 patients with this finding in humans 7 .We report a patient with statin-related rhabdomyolysis and profuse myotonic potentials in the needle EMG with clinical and electrophysiological recovery shortly after the statin interruption.
CaSeA 68 year-old Asian Brazilian woman was admitted with progressive painless weakness for one week, started on the proximal muscles of the four limbs and neck flexors with rapid progression to inability to walk and elevate the limbs. Urine was redbrown in color. Thirty days before the admission she was put on simvastatin due to hypercholesterolemia. Other medication she was taking was enalapril for mild hypertension. There was no personal or family history of myopathy. On neurological examination, abnormal findings were grade 2 (MRC) strength in the proximal lower limb muscles and grade 3 in the proximal upper limb muscles, grade 4 in the distal muscles and hypoactive deep tendon reflexes. No clinical myotonia was detected.A complete blood count, electrolytes, creatinine, glucose, TSH, and free T4 were all normals. Myoglobin was detected in the urine. CPK was 22.260 U/l on the admission day and 55.000 U/l on the third day. AST and ALT were 790 and 750 U/l, respectively. The nerve conduction studies perfomed in both arms and legs showed normal results in the median, ulnar, superficial radial, tibial, peroneal, superficial peroneal and sural nerves bilaterally. The F wave latencies were normal in the median, ulnar, fibular and tibial nerves bilaterally. The needle EMG perfomed with disposable monopolar needle in cervical paraspinal, supraspinatus, deltoid, triceps, abdutor pollicis brevis and first dorsal interosseus in the upper right limb and tibialis anterior, gastrocnemius, vastus lateralis and iliopsoas in the right lower limb showed rare positive sharp waves and fibrillations in the right supraspinatus muscle, as well as a few small amplitude and short duration (SASD) motor unit potentials (MUP) in the right iliopsoas muscle. On the other hand, the needle study showed profuse amount of myotonic potentials in deltoid, supraspinatus, iliopsoas and cervical paraspinal muscles on the right side (Fig 1).Simvastatin was stopped and vigorous hydration was started to prevent acute renal failure. She was discharged two weeks later with normal strength, renal function and CPK levels. A second needle EMG performed 30 days after...