ANTIMALARIAL MYOPATHY: PREVALENCE AND CLINICAL FEATURRES

Background: Myopathy is an uncommon complication of antimalarial treatment. However we reported an strikingly high prevalence in a preliminary study (Ann Rheum Dis 2001; 60(Suppl 1): 80).Objectives: To analyse the prevalence and clinical features of antimalarial myopathy in all patients of the Rheumatology Unit taking this treatment for more than 6 months.Methods: Study period 2 years. We included 119 patients (84 female and 35 male) under antimalarial treatment (112 chloroquine and 7 hydroxychloroquine). Age 57.9 ± 13.8 years. The underlying disease was RA in 70, connective tissue disease in 26, palindromic rheumatism in 14, psoriatic arthritis in 6 and other rheumatic disease in 3. All patients took less than 4 mg/Kg/day of chloroquine or 6.5 mg/kg/day of hydroxychloroquine. The duration of treatment was 47.3 ± 29.4 months, with an accumulated doses of 335.5 ± 214 g. Muscular enzymes (LDH, CPK and aldolase) were determined every 6 months in all the patients. An electromyography (EMG) and a muscle biopsy were performed in the patients with high muscle enzymes (2 or more determinations). The myopathy diagnosis was stablished by histology.Results: 22 p. (18.5%) had a repeated muscle enzyme increase: LDH in 20/22 (91%), CPK in 5/22 (23%) and aldolase in 1/22 (4.5%). An EMG was performed in 18/22 p. 9/18 (50%) myopathic pattern. 15 patients were biopsied Optic microscopy: 3/15 (20%) showed characteristic signs of antimalarial myopathy (vacuolar myopathy). Electron microscopy: 15/15 (100%) p. had an antimalarial toxic myopathy (myeloid and curvilinear bodies). This represents an accumulated prevalence of 12.5%. 9/15 p (60%) had clinical weakness, which means a prevalence of clinical myopathy of 7.5% of the whole groupConclusion: Antimalarial myopathy is relatively common (accumulated prevalence 12.6%). The clinical myopathy is uncommon but not exceptional (7.5%). When a persistent muscle enzymes increase (specially LDH) this myopathy should be ruled out. An ultrastructural study should be performed in order to diagnose this myopathy.Citation: , volume , supplement , year 2002, page Session: Myopathies and soft tissue diseases