If not Myasthenia Gravis, what else?

[mellan]

fairly sudden onset-severe difficulty breathing, muscle weakness-can't climb stairs, can't lift above chest level, recover with rest; over next two months, inc. in difficulty, balance is off, all tasks becoming more difficult, just holding my arms out for 15-20 seconds feels like I ran a marathon, breathing better with steroid inhaler, no difference with  albuterol, face begins to hurt with chewing, smiling, increase odd feeling when swallowing, dev. odd breathing pattern when having long conversation, voice becomes hoarse after speaking for a few minutes straight. Walking/standing still becoming difficult. No general fatigue, no numbness/tingling/no headache-dizziness. Basic labs neg. ACE receptor blocking/binding negative/Rheumotologic tests neg/Lyme neg/slightly elevated d-dimer; neg MRI neg Chest CT neg chest xray; intermittent back pain (like someone shoving fist through spine-neg pulmonary embolism), this is newest sx? What else should I be paying attention to? Does it fit anything else at all?

[Neuro Forum]

Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.

Without the ability to examine you and obtain a history, I can not tell you what the exact cause of your symptoms is. However I will try to provide you with some useful information.

As you mention, easy fatiguiability of the muscles that improves with rest is most typical of myasthenia gravis. Myasthenia gravis is a problem at the neuromuscular junction, the place where the nerve meets the muscles and sends chemicals across to make the muscles contract.

In general, there are several myasthenic syndromes that have similar features, though some may show transient improvement with activity followed by subsequent fatiguing. Negative ACE receptor blocking/binding antibodies do not definitively exclude myasthenia. There is a proportion of patients with myasthenic symptoms who do not have those antibodies. If the diagnosis is strongly suspected on examination, then neurophysiologic studies, such as a study called EMG/NCS which tests how nerves conduct electricity and how muscles respond (and specific types of tests such as repetitive nerve stimulation and single fiber EMG) could be done. If these tests show an abnormality in the neuro-muscular junction, then further blood testing is available to try to elucidate the cause of the problem.

Other cause of muscle fatiguing include certain muscle disorders such as glycogen storage diseases (like Pompe's disease), depression, thyroid problems, and others. Hoarseness of the voice could have ENT causes as well. If you have not been evaluated by a neuromuscular specialist (a neurologist specialized in nerve and muscle disorders) this may be of benefit to you. Breathing difficulties on exertion could have many non-neurologic causes, such as heart and lung problems. If this is suspected by your physicians, evaluation by a pulmonary specialist (a lung doctor) for tests of your respiratory function, and by a heart specialist (cardiologist) may be of benefit to you as well.

Continued followup with your physicians is recommended.

Thank you for using the forum I hope you find the information I have provided useful good luck.

[mellan]

Thanks, I did see a neurologist and he said it's most likely myasthenia, I have a emg scheduled to confirm. They did say the breathing diff. might  be the diaphragm being weak. Thanks for your input.