McArdle’s Disease Overview & Facts

McArdle’s Disease Overview & Facts

Definition of McArdle’s Disease

McArdle’s disease is a metabolic disorder in which skeletal muscle cells are unable to break down glycogen into glucose. Also known as myophosphorylase deficiency or Type V glycogen storage disease. It was first described in 1951 by Dr. Brian McArdle of Guy’s Hospital.


This disease is caused by a missing or non-functioning enzyme, myophosphorylase C, which breaks down glycogen into glucose within muscle cells during exercise. Because this metabolic pathway is interrupted, the energy demands of the cell cannot be met.


People with McArdle’s disease have had the disease from birth, although many people aren’t formally diagnosed until much later in life. Because most individuals who have the condition appear physically healthy but experience premature fatigue, weakness and pain during exercise, McArdle’s disease has historically been confused with being out of shape or unwilling to exercise.

Symptoms of McArdle’s Disease

Symptoms include difficulty during physical activities like jogging, walking up hills or stairs, swimming, or anything moderately intense. Episodes of premature muscle fatigue and pain may be accompanied by muscle contractures known as rhabdomyolysis, which indicates muscle damage require medical attention. Rhabdomyolysis can cause muscle proteins like creatine kinase and myoglobin to enter the bloodstream where they pass in urine, sometimes causing darkened urine (myoglobinuria) which is a warning sign of injury. A “second wind” phenomenon has been observed clinically and anecdotally, in which individuals with McArdle’s disease are able to sustain moderate activities like walking or even jogging following a brief period of warm-up, the duration of which seems to depend on a number of factors including diet and fitness level.


There are few long-term studies published that document the long-term effects of McArdle’s disease on general health. The condition is not by itself life-threatening and people with McArdle’s disease are often otherwise in excellent health.


The presently identified genetic mutations associated with McArdle’s disease follow an autosomal recessive inheritance pattern, requiring two defective copies of the gene for the condition to manifest. Carriers are not known to have symptoms of the disease.


There is no consensus effective therapy for McArdle’s disease. Some physicians recommend that individuals with McArdle’s disease ingest high-sugar beverages or snacks prior to exercise, but this is subject to considerable debate. There have been some clinical studies which show that a diligent regimen of careful aerobic exercise to improve cardiovascular conditioning can yield some relief from symptoms and improve quality of life for people with the disease.

19 thoughts on “McArdle’s Disease Overview & Facts

  1. Tammy McCoy

    I too have a sister that I share this disease with. I am 47 she is 49. We do not have diabetes. But I donnot eat much carbs at all. I stick to a high protein /low carb diet and it works for me. I eat a lot of meat & low carb veggies and very little fruit. Be careful of juices with too much sugar added. I look at every label to see the # of carbs. I found that milk and bread dough in almost any form gives me the most problems. So I just don’t consume. You need to find the foods that cause you the most problems and avoid them. I usually will have a problem 2-3 days following what I have consumed.
    I find low key exercising works best. Tread mill or walking the dog, Stretching and some swimming for short periods until you build your body up. Motrin is the drug of choice, to reduce swelling. I drink extreme amounts of water a day to keep the kidneys flushed. I feel I am the healthiest I have been in years.
    I was diagnosed in 1992 and have been trying to figure out my body ever sense. I do occasionally drink a glass of wine and on a good week will eat potatoes and maybe even pasta, but then I will watch for the next couple of days. Good luck!

  2. Robert

    I have been exercise intolerant for as long as I can remember. In grammar school I remember making up excuses because I couldn’t walk up the three flights of stairs to our classroom after recess (I’m now 57). My whole life I have been unable to do simple things that others could (walk far distances, climb stairs, run, lift weights). I am height/weight proportionate and have a healthy lifestyle. You have no idea how much it means to me to finally know what is wrong with me. When I exercise my urine turns tea colored, I get cramps so bad in my upper legs and groin area that I can’t move.

    I tried jogging and planned to run a 10k race. It took me about a year of training and even after all that, I can’t jog more than a couple of hundred yards before tiring. BUT, if I stop for ten minutes I can than slowly jog for miles. I am a classic “second wind” patient. My six brothers and sisters seem normal. I am a first generation American, my family is of Spanish decent.

    I would like to live a normal life and not be restricted in what I do. I want to be able to exercise and run and walk and climb stairs like a normal person. What can I do to achieve that?

  3. Nola Muller

    My problem which I started noticing in my 50's was the inability to cycle or walk uphill. I do not have heart problems (effort ECG has been done). My symptom is merely that I become slower and eventually have NOTHING to draw on. My legs feel so heavy that I have to actually lie down for 5 minutes. After a short rest like this I can continue uphill for about 200 metres and then have to lie down again. Yesterday I did a hike and found that it is getting worse. My lung capacity has also been checked. All my blood tests which I have had done over the past 8 months have shown nothing more onimous than a cholesterol test in the upper limits of normality. It is definitely to do with load bearing – as soon as I have to carry my weight (71kg and 5'6") I run out of oomph. Please give me a guide line on who to approach in this regard. I live in South Africa

    1. Jill

      Did you ever get control of your symptoms? I am the same age with exactly the same thing going on. Did you have problems for years or did this start later on in life?

  4. Nola Muller

    I am a very healty 61 year old woman who has a personal trainer at gym who gives me cardio and arobic exercise for 1 hour twice a week. I started a Rambling Club and we go walking in Nature Reserves for 3 hours every second Sunday. I use an Orbliptical trainer for 20 minutes each evening on the heaviest setting.So am not unfit.



  6. Jim Ottesen

    @Jim Ottesen

    @Jim Ottesen
    It sounds like you do have a neurological problem so we should
    start with a neurologist – have you been to one yet? Regular
    doctors are essentially clueless when it comes to a McArdle’s Disease diagnosis. You should ask your new doctor to check your CPK level
    soon after you have a serious pain problem and while he’s looking at
    blood levels check your kidney function, liver function, and Vitamin D level. Your urine must also be checked for blood and protein and the
    usual checkd for bacteria, etc. Do you presently have any of the results of these tests from the past? How long have you had this pain problem. Is it only the extremities? Do you have any of the major heath problems (diabetes, high blood pressure, overweight)? Any family
    member have the same symptoms. Is there a geneticist in your area?
    Please get back with me with some answers as we can put you on the right path.

    Best regards,


  7. Adrienne G

    I have had issues going up stairs and been in tears…I need a diagnosis and have seen nine Dr.s in the past year…PLEASE— what kind of Dr. do I need ?????

  8. Jim Ottesen

    Heidi and Lee,

    I am 72 and was diagnosed two years ago. I find that you can avoid
    most pains by doing nothing which causes more than a five second period
    of holding, pushing, lifting or straining in any way. That is the magic
    number. Clearly, walking or swimming can also cause problems if done to
    excess. Once you have the pain, drink lots of fluids, take Tylenol (if
    doctor approved, do a Hemastix check and see your doctor if your reading
    is too high. Often, in my case, gentle stretching and massage seem to work most of the time. Always remember, if the pain is too great for too long, your kidneys could be affected and your doctor needs to do a
    blood check for CPK and kidney function and a urine test for blood and
    protein. I encourage mild exercise during your lifetime, but no weight
    lifting and no straining for more than the five seconds I mentioned.

    I hope this helps.

    Good luck and God bless.


  9. Lee Clendennen

    Heidi, I am 71 years old have lived with this problem all my life. I can never remember being able to walk long distances and could never run more than fifty yards. I was not dianosed until age 64, doctors gave all kinds of reasons for the problem. I finally saw a young neurologist that knew about McArdles. He took a mussle bioposie from my thigh. That is how I found out what i have.
    I did manual labor for the first 14 years of my working carrier. I was fortunate to get into upper management at 32. I could not have lasted much longer doing the manual labor part. I am still working at present, simply to keep me ocupied. If I am not busy I worry to much about what my body is doing. I cannot climb a flight of stairs without stopping at least once. I have to staop and rest every 50 yards while walking on flat surfaces.
    I have found nothing that gives me relief other than a clasic coke or a sniker bar. That is not very long term releif.

  10. Kyle

    I am nearly in my mid 20s, & soon getting tested for McArdles & other possible metabolic muscle diseases. I get cramping and aches in leg muscles from running, sometimes for months afterwards. My Neuro-Muscular Dr is scheduling me for a muscle biopsy. Can anyone tell me their experience how painful and/or the scar the biopsy leaves behind? Can anyone mention more in depth, the symptons they get in muscles with this disease?

    1. luke

      yes, i have had it done by the top neurologist in the country. Dr, jerry Mendell out of Ohio state University. the procedure can be done by a local anestetic(spelling). and you can be awake if you want. each time recoup time was short 2 weeks maybe. it just feels like someone gave you a charlie horse…. most times done on opposite limbs of the body at same time. usually shoulder and opposite calf or thigh.they usually give adequate pain meds for duration of recovery


    My brother just found out he has McArdles and I will be tested the end of the month. We both realized we had the same symptoms for the last 10 years. We did not know why. We have 2 siblings that do not have this. It was not till he had recently been to a heart doctor, (for another problem), and told him about the muscle problems and he sent him to a specialist. I had been to a sports doctor in the past, but got no answers. I have muscles problems on a weekly basis. I get about 2 muscles a week that swell up and I am in pain 2 or 3 days. Does anyone know if rubbing the muscles help when they are swollen? I am glad to have an answer to why i cannot walk up more than one flight of stairs and uphill kills my legs and even the small things can make my muscles go crazy. I always thought I just wasn’t in good condition and needed to work out more. But in my heart I knew something was not right. I wish I would have know this 30 years ago.


    Hi, My name is Aldin Delfino,I am 30 years old, and Im from Uruguay.
    My father has have a disease of similar symtoms as discribed here (myoglobinuria after long term exercise, and many episodes ended in kidney failure due to the myoglobinuria). I have never had symtoms and I excersise often (Lately Ive been swimming for 3 hours a week, and gym 3 hors a week also), but I usualy dont suffer from crumps or muscle pain or fatige. I have similar muscle structure as my father (my muscles are not shaped, except for the calfs that are big). This year Ive had 2 miscarriage and all the blood analysis are normal, and all the doctors Ive asked say that there is no cause, and dosent have a cause, and may be genetical disorder, but they cant find it out.
    I was wondering wether my father disease has anything to do with the miscarrige? Do you have any case similar?
    Thank you in advance, Regards,

  13. Jim Ottesen


    You will have better luck finding a seasoned neurologist that
    has some experience with the bad “M.” He or she will have better luck
    by doing a consult with the experts after your person has more facts.
    Now, please listen to me, stop the heavy stuff, the lifting, and the
    stressing. You do not want to damage your kidneys! Before you hire
    your neurologist, ask him if he has experience with “M”, if he has access to a facility that can perform the ischemic forearm test and
    the biopsy of your thigh to test for “M” and other possibilities.
    The ball is back in your court – let’s get some answers! Let us hear
    how you progress. Jim Ottesen
    a hospital equipped to do the ischemic forearm test

  14. Jim Ottesen


    I am so sorry to hear of the problems you and your daughter are suffering. First, both of you need a good neurologist to look
    at the risks of fibromyalgia, McArdle’s Disease and other possibilities.
    Your neurologist must be seasoned and experienced in the identification
    of the illnesses I have mentioned. He or she must be able to perform
    the ischemic forearm test and access to a facility that has the expertise to do a biopsy if needed. In the meantime, Have your doctor
    request a complete blood chemical profile with CPK a must. Your
    daughter should also let this be a starting point. When all this is
    done, make sure you get a copy of all the tests the “others” have done to date – your neurologist will need these numbers. Let us know how
    things go, but don’t stop until you have an answer. You and your daughter should not continue to suffer – life is too short! But, you
    must lead the way. Good luck. Jim Ottesen

  15. robert

    I’ve had a neuromuscular/high ck problem with myalgia for about 5 years
    now, and a variety of symptoms prior to that made no sense.
    I had the elevated CK discovered by accident, so I’m not really sure when that started. I have massive fatigue, I get cramping when I’m doing something, then if I stop, it generally goes away. If I exercise
    even a little I get pain, cramping, and fatigue, and sucrose makes me
    very very tired. I do have a low acid-maltase enzyme, but that’s all
    I know and so no dx on that issue. If I for example, try and carry
    some heavy load I get winded and muscle damage that seemingly takes
    weeks to heal. In fact, I have two areas that seem permanently damaged.
    They have no explanation. Any suggestions? I’ve tried to conctact the
    specialists mentioned here but they have no responded, that’s weeks ago.

  16. karen

    I have been ill for over 10 yrs now with 90 % of the subjective symptoms. I have seen at least 19 practitioners, PT, accupuncture, pain clinics, facet blocks, and cervical spine fusion. All with no result.
    I am tired, mentally and physically.
    What type of physician should I see for this, and a biopsy? I ask as now my 24 yr old daughter has many of my symptoms and since childhood was told she has “chronic fatigue syndrome.” I don’t believe that.
    Can you direct me please.
    Thank you for your time, Karen


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