Patients on antimalarials at risk for myopathy

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Patients on antimalarials at risk for myopathy



Aug 22, 2005



Janis

Barcelona, Spain - Antimalarials caused persistent muscle-enzyme

disturbances in 18.5% of rheumatic disease patients and clinical

myopathy in 6.7% in a prospective study reported online August 11,

2005 in ls of the Rheumatic Diseases [1].



" The prevalence of antimalarial myopathy is higher than previously

recognized when the muscle-enzyme determination is used as a

screening method. When a persistent muscle-enzyme disturbance is

observed, a clinical and electromyographic study should be performed

periodically to detect earlier the development of a clinical

myopathy, " say the researchers, led by Dr Enrique Casado (Parc Tauli

University Hospital, Barcelona).

Muscle-enzyme changes in 18% of patients

This prospective study included all patients with rheumatic diseases

taking antimalarials over a three-year period. Serum muscle enzymes

were measured at inclusion and every six months thereafter. Patients

who had muscle-enzyme disturbances at any point were further assessed

with muscle strength electromyography (EMG) and muscle biopsy. The

study included 111 patients taking chloroquine and eight taking

hydroxychloroquine.

Antimalarial myopathy was defined as the presence of the specific

ultrastructural microscopic findings associated with persistent

muscle-enzyme disturbances, regardless of clinical symptoms.

Muscle fiber showing characteristic antimalarial myopathy myeloid

bodies (arrow) and curvilinear bodies (asterisk). [Click on the image

to see a larger view.]

Clinical antimalarial myopathy was defined as the presence of

antimalarial myopathy associated with an objective muscle weakness,

through direct examination of proximal and distal muscles of upper

and lower limbs and neck flexor muscles.

Casado reported that 22 patients (18.5%) had persistent muscle-enzyme

disturbances. These involved lactate dehydrogenase (LDH) in 19/22

patients, creatine kinase in 7/22 patients, and aldolase in 3/22

patients. Although LDH is not specific for muscle disease, levels

normalized in all of the patients who stopped antimalarial drug therapy.

Fifteen patients were biopsied. Light microscopy showed antimalarial

myopathy in 3/15. Electron microscopy showed antimalarial myopathy in

all 15 patients.

Of these 15 patients, 11 had myopathy at the time they entered the

study, and four developed myopathy during follow-up. Eight of 15

patients with biopsy-proven myopathy also had muscle weakness, for a

prevalence rate of 6.7%, and all eight also had myopathy on

electromyography.

" Antimalarial myopathy was demonstrated in 12.6% of the patients

included in the study, " Casado writes. Thirteen patients were being

treated with chloroquine and two with hydroxychloroquine.

The authors note that the incidence of myopathy was much higher in

their study than in previous studies, but they point out that this

study was prospective and also used a sensitive screening test:

muscle-enzyme changes. Earlier studies were smaller, retrospective,

and uncontrolled, and no other prospective data on the incidence of

antimalarial myopathy have been published, they add.

Casado emphasizes that antimalarial myopathy diagnosis should be

confirmed by biopsy. " In these cases an ultrastructural examination

is absolutely mandatory to detect the characteristic tissue deposits

that confirm the diagnosis of an antimalarial myopathy, since light

microscopy has numerous false negatives (80% in our series). "

May be masked by musculoskeletal symptoms

Myopathy is a recognized toxic effect of antimalarials, along with

retinal problems. These toxicities occur with long-term

administration of the drugs and stem from accumulation of

intracellular deposits, mainly in the retina and muscle, the authors

explain.

The muscle toxicity may be difficult to spot in patients who already

have musculoskeletal symptoms, they comment. In this study, patients

were being treated with antimalarials for rheumatoid arthritis (69

patients), palindromic rheumatism (14), Sjörgen's syndrome (11),

systemic lupus erythematosus (9), undifferentiated connective tissue

diseases (7), psoriatic arthritis (4), and other rheumatic conditions

(5).

" Initial symptoms of muscular injury are characteristically mild.

However, painless proximal weakness in both upper and lower

extremities may become more severe in time, " the authors write. " In

many cases, this clinical feature is masked by the musculoskeletal

manifestations of the underlying disease, which could explain why the

diagnosis of antimalarial myopathy is usually difficult and often

delayed. "





Source 

Casado E, Gratacos J, Tolosa C, et al. Antimalarial myopathy: an

underdiagnosed complication? Prospective longitudinal study of 119

patients. Ann Rheum Dis 2005; DOI:10.1136/ard.2004.023200. Available

at: http://ard.bmjjournals.com. 

http://www.jointandbone.org/viewArticle.do?primaryKey=545609