External ophthalmoplegia with ragged-red fibres and acetylcholine receptor antibodies

The cases of two elderly women with external ophthalmoplegia, generalized muscle weakness and serum anti-acetylcholine receptor antibodies, are presented. The electophysiological studies showed a myopathic pattern but no indications of myasthenia after repetitive stimulation. The edrophonium test was negative and there was no response to anticholinesterase medication. In addition, elevated serum lactic acid levels and ragged-red muscle fibres in the muscle biopsy, were observed in both patients. These findings are discussed in relation to the fact that anti-acetylcholine receptor antibodies are diagnostic of myasthenia gravis, whereas ragged-red fibres and elevated lactic acid are correlated with mitochondrial myopathies.