Objectives To analyse the prevalence and clinical features of chloroquine myopathy in a cohort of out-patients in a Rheumatology Unit.
Methods Prospective study of 119 patients (84 female and 35 male), aged 57.8 ± 13.7, taking antimalarials (112 chloroquine, 7 hydroxychloroquine) for more than 6 months. They were evaluated during 2 years. The underlying disease was RA in 69, connective tissue disease in 22, palindromic rheumatism in 14, spondyloarthropathy in 7 and other rheumatic disease in 7. Muscle enzymes were determined in all patients and an electromyography (EMG) was practised in patients with repeated increased determinations. Patients with altered EMG were biopsied.
Results Laboratory: 18 patients (15%) had a repeated increase of muscle enzymes: LDH in 17 patients, CPK in 5 and aldolase in 1 patient. EMG: practised in 13 patients, showed a muscular involvement in 6. Two patients are pending and 3 were dead before the exam. Muscle biopsy: 6/7 patients had a chloroquine myopathy (optic and electronic microscopy); 1/7 patients had a steroid myopathy. Two patients (RA) with chloroquine myopathy had an associated inflammatory myositis. Clinical features: 6 patients with chloroquine myopathy (5 RA and 1 spondyloarthropathy) represents an accumalated prevalence (2 years) of 5%. The duration of treatment was36 ± 21 months (rest of the group 40 ± 31), with cumulative doses of 203 ± 25 g (rest of the group 305 ± 243 g). All patients presented weakness and had other simultaneous muscle involvement factors (1 cervical myelopathy, 2 hypothyroidism, 3 hypovitaminosis D and 1 prolonged bedrest) at clinical diagnosis.
Conclusion Toxic chloroquine myopathy is not an excepcional event (accumulated prevalence 5%). When an increase of LDH and/or CPK is present we should to rule out this complication. The presence of other factor with muscle involvement probably makes worse the weakness and gets better its detection.
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