Neurológia pre prax 6/2016

Toxic myopathies

Damage of skeletal muscle by a toxic substance can lead to toxic myopathy. In most cases there is a toxic effect of medicaments, in a lesser extent effects of abuse substances, biological or chemical toxins. A toxic substance can damage contractile elements (actin, myosin) or some other muscle proteins, individual organells (e.g. microtubulls), can disturb muscle cell metabolism (e.g. mitochondrias), muscle membrane with ionic channels. Individual patophysiological mechanisms lead to various pathological or clinical pictures of toxic myopathies. There is an increasing number of medicaments with myotoxic effects and there are more patients with variably marked myopathy with pharmacological cause. The most common pharmacologically induced toxic myopathy is attributed by statins. The painless myopathy is associated with therapeutic use of chlorochin. Therapy with zidovudine (used in HIV therapy) may be associated with proximal muscle weakness, with muscle pain and mitochondrial damage. Long-lasting steroid therapy may cause painless weakness of proximal muscles with prominent typ II fibre atrophy. Critically ill myopathy is characterized by muscle weakness, development of muscle atrophy, characteristic EMG findings. In muscle biopsy is a prominent loss of thick fibers (myosine). Early disclosure of myopathy and identification of the toxic medicament is a basis of therapy and prevention of toxic myopathies.

Keywords: medicaments, toxic myopathy, necrotizing myopathy, mitochondrial myopathy, rhabdomyolysis, muscle biopsy