What is Corticosteroid Induced Myopathy?
Corticosteroid-induced myopathy is a common condition that may occur as a side effect from prolonged use of certain medications, specifically oral or intravenous glucocorticoids. This was first discovered in 1932 by Harvey Cushing, who noticed it among the symptoms of Cushing syndrome. By the 1950s, as more people started using corticosteroids for treatment, this condition started becoming more familiar.
This condition usually develops gradually and primarily affects the muscles in the pelvic area. It results in muscle weakness and shrinkage, but without any pain. There is also a version of acute steroid-induced myopathy that is found in critical care situations. Typically, patients will have normal levels of creatine kinase, a protein found in muscles, and won’t show any other signs of inflammation. When examined by an electromyogram (EMG), a test that measures muscle response, the results will be normal. A biopsy will show that type 2b fast-twitch muscle fibers have shrunk.
Diagnosing this condition requires a careful lookout for it and can be confirmed when muscle weakness starts to improve after three to four weeks of reducing steroid use. The total recovery may take months to up to a year. Alternatives to avoiding this condition include switching to a different type of glucocorticoid or changing the dosage schedule. Physical therapy that includes resistance and aerobic exercises can also help prevent and treat this condition, as some studies have proven.
Therefore, doctors should have a screening program for corticosteroid-induced myopathy for those patients who may be susceptible. They should also prescribe physical therapy as a preventive measure and treatment for this condition.
What Causes Corticosteroid Induced Myopathy?
Corticosteroid-induced myopathy is when muscle weakness is caused by taking corticosteroids, a type of medication. This usually happens when patients take high doses of this medication – more than the amount that is found in a 10mg prednisone tablet – for over four weeks. It’s also possible for symptoms to appear quicker if much higher doses, like 40 to 60mg of prednisone each day, are taken for two to three weeks.
This side effect is most common with corticosteroids taken orally or through an IV. However, there have been rare cases when it was caused by corticosteroids that were inhaled or injected into muscles, joints, or the spine.
Particularly in intensive care settings, where patients are on ventilators and receiving paralytics (drugs that relax muscles), taking more than 60mg each day of another type of corticosteroid, methylprednisolone, for 5 to 7 days has also been linked to acute muscle weakness.
Risk Factors and Frequency for Corticosteroid Induced Myopathy
Corticosteroid-induced myopathy is a type of muscle disease that commonly occurs due to the extended use of corticosteroids, with around 50% to 60% of long-term users being affected. People of all ages can experience this condition, but it is mostly seen in the elderly because they have less muscle mass. People battling cancer are also at a higher risk. Additional factors that can increase the risk of this muscle disease include pre-existing muscle or spinal cord injuries, long-term respiratory illnesses, poor nutrition, and a lack of physical activity.
- Furthermore, women are more susceptible to it, though why this happens is not yet clear.
- People who are seriously ill and need help with breathing may be at a higher risk if they receive high doses of steroids alongside muscle-relaxing medications.
- This can lead to a problem called acute steroid-induced myopathy, which could take weeks to get better.
- There have been cases where patients who were not on ventilators developed an early onset of steroid myopathy within two weeks of starting moderate doses of steroids. This includes unusual impact on muscles like the vocal cords.
The specifics of this condition can vary greatly from person to person, which makes it complicated to study and understand.
Signs and Symptoms of Corticosteroid Induced Myopathy
Corticosteroid-induced myopathy is a condition that leads to muscle weakness, particularly in the muscles around the hips and shoulders. It often happens after using corticosteroids for a long time and is associated with muscle shrinkage rather than pain. People with this condition often find difficulty in standing up from a sitting position, climbing stairs, or performing activities that require lifting their arms above their heads. It also affects both sides of the body equally. The condition usually develops gradually, over weeks to months, after starting corticosteroid use. It is more likely to occur when higher doses of the medication are used.
On physical examination, evidence of muscle weakness may be found in up to 20% of patients, though up to 60% may report feeling weak. The physical examination may also reveal reduced reflexes in the affected limbs. Importantly, no signs of nerve or sensory loss, or involvement of brain nerves, will be found that could suggest a problem with the brain or spinal cord.
Long-term use of glucocorticoids like corticosteroids can result in other health issues. These might include symptoms of Cushing syndrome like a round face and unusual fat distribution.
- Metabolic problems such as obesity and diabetes
- Endocrine disorders, such as adrenal insufficiency and high cholesterol
- High blood pressure
- Skin and bone disorders, including osteoporosis and bone death
- Increased risk of infections
- Stomach inflammation
- Eye problems, such as cataracts and glaucoma
- Mood/neurocognitive side effects
So, patients can present with various complications resulting from long-term use of steroids.
Testing for Corticosteroid Induced Myopathy
Corticosteroid-induced myopathy is a condition that affects the muscles, causing weakness, and it can be challenging to diagnose. It requires doctors to be highly alert due to unremarkable lab and biopsy results. Particular lab tests like creatine kinase, aspartate aminotransferase, lactate dehydrogenase, and aldolase usually show normal results, although there might be some elevation in the early stages or in severe cases.
A muscle biopsy, a procedure where a small piece of muscle tissue is removed for testing, isn’t typically necessary for diagnosis. If performed, the biopsy might show some signs of muscle wear and tear but rarely any evidence of inflammation or severe muscle damage. These results differentiate corticosteroid-induced myopathy from other muscle-related diseases that feature inflammation.
When doctors use Electromyography (EMG) – a test that evaluates muscle and nerve function – the results are usually normal. Occasionally, they might show a minor decrease in motor unit potentials. This pattern occurs because EMG measures all muscle fiber activity without distinguishing the specific type that’s most affected by this condition.
Imaging tests, like MRI, are not commonly used to diagnose corticosteroid-induced myopathy, but can be utilized when considering other possible conditions. It is sometimes difficult to tell if muscle weakness in a patient already on steroids for a muscle-related disease is due to the progression of their current condition or the development of corticosteroid-induced myopathy.
Ultimately, the diagnosis of corticosteroid-induced myopathy is confirmed if the patient’s symptoms improve after reducing or stopping the use of corticosteroids, which are a class of medication often used to reduce inflammation.
Treatment Options for Corticosteroid Induced Myopathy
Corticosteroid-induced myopathy, a condition causing muscle weakness that can be a side effect of steroid medications, often goes unnoticed. This is because the symptoms are frequently mistaken as part of the illness that the steroids were prescribed to treat. Thus, doctors need to be aware of this possible side effect if a patient reports muscle weakness while taking corticosteroids.
The primary way to treat corticosteroid-induced myopathy is to reduce or ideally stop the steroid medication. But, this must be done carefully, as there’s a risk of adrenal insufficiency (when your adrenal glands don’t produce enough hormones) and worsening of the original illness during the process. If it’s not possible to stop the steroids, switching from a fluorinated glucocorticoid (like dexamethasone) that is more potent and can create more side effects, to a non-fluorinated glucocorticoid (like prednisone or hydrocortisone) could be a solution.
For patients with primary brain tumors who are on dexamethasone, an anticonvulsant medication called phenytoin can be added to help reduce the risk of developing corticosteroid-induced myopathy. Apart from this, non-daily dosing regimens are another option. However, whenever possible, it’s better to use treatments that minimize steroid use.
Confirmation of corticosteroid-induced myopathy comes when muscle strength improves within 3 to 4 weeks of reducing steroid use, although full recovery may take many months to a year. In addition, physical therapy involving aerobic and resistance exercises can help prevent and treat this condition. In fact, a 6-month regimen of monitored resistance training proved to significantly reverse muscle atrophy and improve muscle strength in a study involving heart transplant recipients on chronic glucocorticoid treatment.
There are experimental treatments being researched, such as specific supplements and hormones, but these are not currently recommended as they haven’t been conclusively evaluated in humans.
What else can Corticosteroid Induced Myopathy be?
There are a variety of medications and substances which are known to lead to drug-induced muscle weakness or myopathy. These include colchicine, anti-malaria drugs, anti-HIV drugs, and substances like alcohol and cocaine. Myopathy can also result from inflammatory diseases, such as polymyositis and dermatomyositis, so it’s crucial to eliminate these possibilities when diagnosing drug-induced myopathy.
An example of such a drug is statins, which have been linked to myopathy. This usually shows itself as muscle pain and inflammation. In some rare cases, people using statins can develop a type of myopathy called autoimmune necrotic myopathy. Muscular weakness can also be caused by using a combination of drugs that are muscle-damaging by nature, such as hydroxychloroquine and glucocorticoids.
Additionally, corticosteroid-induced myopathy is typically characterized by non-inflammatory muscle weakness, which is distinct from the muscle disorders caused by inflammatory diseases. A muscular biopsy can help distinguish between the two, as it will show a different type of muscle tissue damage
Another thing to note is that certain autoimmune and inflammatory syndromes, like systemic lupus erythematosus, Sjögren’s syndrome, scleroderma, and rheumatoid arthritis, can cause muscle inflammation and weakness. These conditions need to be considered while diagnosing corticosteroid-induced myopathy. In cases of dermatomyositis, which increases the risk of cancer, paraneoplastic syndromes could also be causing myopathy.
Endocrine disorders affecting organs like thyroid, adrenals, or pituitary gland, electrolyte imbalances, and nutrient deficiencies, such as low vitamin D levels, can also cause muscle weakness. Metabolic and congenital muscle disorders resulting from abnormal carbohydrate, fat, or purine metabolism are rare causes of muscle weakness with unique symptoms. Overall, numerous differential factors can cause muscle weakness, and each patient needs to be evaluated based on their clinical context and symptoms.
What to expect with Corticosteroid Induced Myopathy
Corticosteroid-induced muscle weakness is typically reversible, showing improvements within 3 to 4 weeks once the dosage of corticosteroids is gradually reduced. However, full recovery can sometimes take up to a year. Currently, there are no known treatments to speed up this process other than reducing the use of corticosteroids.
Transitioning from certain types of steroids such, as dexamethasone, to other versions (like prednisone) could sometimes be beneficial. Please keep in mind that patients who have been on steroids for a long period should not suddenly stop taking them. Instead, they should gradually reduce their steroid dose to prevent issues such as adrenal insufficiency or worsening of the condition for which they’re using steroids.
Additionally, physical therapy that includes both resistance and endurance exercises can help manage and prevent steroid-induced muscle weakness. The approach to these exercises should take into consideration the patient’s initial function and condition.
Possible Complications When Diagnosed with Corticosteroid Induced Myopathy
Using corticosteroids for a long time can lead to a muscle condition called corticosteroid-induced myopathy. This condition can cause severe muscle weakness, which can lead to other health problems and even death in some cases. People with this condition often have a low quality of life because they struggle with daily tasks. They also have a high risk of falling and getting injured.
If a person has asthma that is resistant to treatment and they’re taking corticosteroids for a long time, it’s worth considering corticosteroid-induced myopathy. This condition may be a reason why the asthma is not getting better and why the person might have long-term respiratory failure.
Preventing Corticosteroid Induced Myopathy
Patients should regularly be informed about the benefits and risks associated with the use of corticosteroids, which can sometimes cause muscle weakness, a condition known as corticosteroid-induced myopathy. They should be told to reach out to their healthcare provider if they start to experience any signs of weakness. It’s also important for patients to know that staying physically active can help both prevent and lessen the impact of this muscle weakness. As part of a strategy to help avoid and treat this condition, patients should be recommended to include physical therapy in their routine.
