Critical Illness Myopathy and Other Causes for Myopathy

00:00 Now, let’s move to critical illness myopathy. This is a different type of toxic myopathy. It’s characterized by prominent muscle weakness and atrophy. And that atrophy is usually profound. It occurs with prolonged hospitalization, typically 7 to 10 days or more of a hospitalization. And the risk goes up substantially in patients who are in the ICU as compared to other places in the hospital. There’s a number of different factors and findings that can occur in these patients. We can see a thick filament myopathy, a critical illness myopathy, even a necrotizing myopathy can occur in hospitalized patients. And the key is to know that this can occur and it tends to develop the more the patient is in the hospital. Now let’s move to medications and we’re going to quickly review some of the medications that are associated with myopathies. You’ll see that the list is really long. And I don’t need you to know all medications, but know that they exist. And this is a good list to consult when evaluating a patient who may have a toxic myopathy that your concern could be from medications. So what are some of the medications associated with myopathy? Well, heart therapy is one to think about. This is antiretroviral therapy given to patients with HIV or AIDS. Myopathy is classically associated with AZT, but can be seen with other medicines.

01:20 Colchicine can contribute to myopathy, a colchicine myopathy. Patients present with muscle weakness after starting colchicine and after its administration and this can be seen in an acute gouty attack. Anti-malarial myopathy comes from malarial medications, chronic alcohol myopathy from alcohol. Again, the list is quite long. Let’s look specifically at some of the medicines on that list. These are medicines other than steroids and other than statins that contribute to myopathy. The typical presentation is what you’d expect for a muscle disorder; proximal weakness, normal sensation, normal reflexes, no elevation in CK. And we think about alcohol, drugs of abuse, hypokalemia is an electrolyte that can contribute to this, aminocaproic acid, phenytoin, L-tryptophan, AZT, cyclosporine, IV corticosteroids, oral corticosteroids, anti-malarials, amiodarone, the list goes on. Again, some things I’d like for you to know of, but this is a list to consult when evaluating these patients in the clinic. What is the type of pathology that occurs from medication-induced myopathies? There’s a lot of different things that drugs can do to the muscle. They can cause myonecrosis or damage of the muscle and death. Inflammatory myopathy they can precipitate an inflammatory myopathy, like statins. Mitochondrial myopathy, and that’s what we see with AZT with the inclusions of ragged red fibers within the muscle, myosin loss in critical illness myopathy, type 2 fiber loss, vacuolar myopathy, and other types of myopathic changes. And again, I don’t need you to know all the details of what can happen, but medicines can do a number of different things to the muscle.