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Mitochondrial, Inflammatory, Endocrine and Drug Induced Myopathies

by Carlo Raj, MD
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    00:01 We’ll walk through a few mitochondrial myopathies.

    00:03 To begin with, remember, in us, as you carry out as humans, we have two different types of DNA, right? We have our somatic or our nuclear DNA, and then we have our mitochondrial DNA.

    00:17 The mitochondrial DNA is something that we inherit from mama, right? From our mothers.

    00:21 So here, there’s a couple of ones that we have to know about, definitely know about mitochondrial encephalomyopathy with lactic acidosis and stroke-like symptoms.

    00:29 In other words, that’s MELAS.

    00:31 The other one is -- Pay attention to RRF, that’s ragged red fiber.

    00:38 These are the ones that you’ve also talked about in biochemistry.

    00:41 Hence, I am not elaborating on the abbreviation.

    00:45 Either maternal inherited or sporadic, mother may be unaffected carrier though.

    00:52 Frequently accompanied by other neurologic manifestation.

    00:55 For example, MELAS, Mitochondrial encephalomyopathy, lactic acidosis, and, what does S stand for? Stroke-like symptoms.

    01:04 Our muscle biopsy, what would you expect to see? What’s that RRF stand for? Ragged red fiber, which contains what? You must know what ragged red fiber contains.

    01:15 Accumulation of glycogen and what’s known as your lipids.

    01:20 Our topic here is inflammatory myopathy.

    01:23 Begin by looking at dermatomyositis.

    01:26 Allow the name to speak to you.

    01:27 What does derma mean? Skin.

    01:29 What does myo- mean? Muscle.

    01:31 Hence, we’re doing our skeletal muscle diseases.

    01:35 Then we have polymyositis.

    01:38 And finally, we have what’s known as our inclusion body myositis.

    01:42 In other words, inflammation.

    01:45 Shoulder and hip girdle weakness is present.

    01:47 Oh, be careful, huh.

    01:49 There was actually a condition that we called what? Limb and hip girdle myopathies or dystrophies.

    01:59 So, be careful with those, right? Versus here, we’re dealing with shoulder and hip, but I have to give you further detail, as will your clinical picture.

    02:08 Don’t worry.

    02:10 Relative sparing of, once again, the ocular and bulbar, and cardiomyopathy, once again, less frequent.

    02:15 So, those are nonspecific.

    02:17 We see this earlier with limb and girdle muscular type of dystrophy.

    02:21 So what is it about these conditions that is more specific? Let’s take a look.

    02:27 First, we’ll take a look at dermatomyositis.

    02:30 Most frequently seen in children.

    02:32 What are you going to find? Well, when seen in adult, often associated with underlying malignancy.

    02:38 Derm, will begin with the skin.

    02:40 Around the eyes, you have something called a heliotrope rash.

    02:45 So, it’s purplish discoloration of the eyelids.

    02:48 Memorize that.

    02:49 Dermatomyositis.

    02:51 The first manifestation is going to be skin, more common in children.

    02:55 If it’s adult, then it’s malignancy.

    02:58 Then you have what’s known as Gottron lesion, and this Gottron lesion are going to be that around the knuckle.

    03:04 So, erythematous, which means what? Red scaly lesion over the knuckles.

    03:08 In other words, your metacarpophalangeal joints.

    03:11 Associated cardiac conduction abnormality, congestive heart failure, or perhaps even, interstitial lung disease.

    03:18 Just keep those in mind because not only could you have then your skin issues.

    03:22 Ah, you could have issues with the muscle as well.

    03:25 Dermatomyositis.

    03:27 It is steroid responsive.

    03:32 Here, we have polymyositis.

    03:35 These are more common in older individuals.

    03:37 Condition: Steroid responsive.

    03:40 All that I wish to say about polymyositis.

    03:43 Inclusion body myositis: Late middle aged to elderly predominance.

    03:47 I just want to make sure that you’ve heard of such conditions.

    03:50 Early weakness of finger flexors and ankle dorsiflexors.

    03:55 Steroid-resistant, inclusion body myositis.

    04:01 Here, we’ll take a look at endocrine myopathies.

    04:04 Your patient may have thyrotoxic myopathy.

    04:08 Often subclinical, brisk reflexes.

    04:11 In other words, there could be an increase in thyroid hormone.

    04:15 And you have creatinine kinase, typically, would be normal.

    04:18 Versus hypothyroidic type of myopathy.

    04:21 So, think about decreased T3, T4.

    04:23 Proximal weakness, fatigue, myalgia.

    04:26 Delayed relaxation, think of your patient with hypothyroidism, everything is slowed down.

    04:31 Creatinine kinase is moderately to severely elevated.

    04:35 Steroid myopathy could be caused by either endogenous or exogenous causes.

    04:39 CK is typically normal.

    04:42 With drug and toxin induced myopathy, there are too many causes to list, but here are some important ones.

    04:49 HMG-CoA reductase inhibitors, your statins.

    04:52 Do not forget, may then cause necrotizing, what’s known as rhabdomyolysis.

    04:56 You’d find your creatinine kinase to be ridiculously high.

    04:59 Obviously, not very common but something very much to keep in mind.

    05:04 Fluorinated glucocorticoids or dexamethasone.

    05:07 Alternate day dosing lessens the risk.

    05:09 Remember that by taking steroids, there’s every possibility that a myopathy could set in.

    05:15 Zidovudine, your patient is on highly active antiretroviral therapy, heart regimen.

    05:23 There is a possibility of mitochondrial myopathy with zidovudine, AZT.

    05:29 Cimetidine, H2 blocker, maybe your patient is suffering from a gastric ulcer.

    05:34 And so therefore, you want to block the acid production, and in the process, may result in inflammatory myopathy.

    05:40 Keep that in mind along with, obviously, gynecomastia and such.


    About the Lecture

    The lecture Mitochondrial, Inflammatory, Endocrine and Drug Induced Myopathies by Carlo Raj, MD is from the course Polyneuropathy. It contains the following chapters:

    • Mitochondrial Myopathies
    • Inflammatory Myopathies
    • Endocrine Myopathies
    • Drug/Toxic Induced Myopathies

    Included Quiz Questions

    1. Charcot Marie Tooth disease
    2. MELAS
    3. MERRF
    4. Progressive external ophthalmoplegia
    5. Kearns-Sayre syndrome
    1. Both males and females are 100% affected in the first generation siblings.
    2. 50% males and 50% percent females are affected in the 1st generation of siblings
    3. Males are affected and females are carriers of the 1st generation of siblings.
    4. 50% males are affected and 25% females are affected of the 1st generation of siblings.
    5. The first generation of siblings are not affected but the 2nd generation males are only affected.
    1. Glycogen and neutral lipids
    2. Mucopolysaccharides and protein
    3. Lysosomes and mitochondria
    4. Mucin and melanin
    5. Immunoglobulins and inclusions
    1. Dermatomyositis
    2. Limb-girdle dystrophy
    3. Duchenne muscular dystrophy
    4. Becker dystrophy
    5. Inclusion body myositis
    1. Thyrotoxic myopathy
    2. Hypothyroid myopathy
    3. Duchenne muscular dystrophy
    4. Limb-girdle muscular dystrophy
    5. Myotonic dystrophy
    1. Mitochondrial myopathy
    2. Inflammatory myopathy
    3. Inclusion body myositis
    4. Necrotizing myopathy
    5. Endocrine myopathy

    Author of lecture Mitochondrial, Inflammatory, Endocrine and Drug Induced Myopathies

     Carlo Raj, MD

    Carlo Raj, MD


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