Q: My 22 years sister is suffering from myasthenia gravis for the last 15 years. She is taking Pyridostigmine (60 mg). In the last five years, her physical appearance has changed badly and her right part of the body has also bent slightly. Moreover, she is unable to stand straight. What causes myasthenia gravis? How can it be treated?

A:Myasthenia gravis is an autoimmune disease, one amongst many that can affect human beings.

Whenever micro-organisms like bacteria, viruses etc. or certain unwanted proteins (antigens) enter the bloodstream, body's defence mechanisms are activated. These lead to production of weapon-proteins (antibodies) which are aimed at neutralising the offending antigens. However, some people have a possibly genetic (?) fault in the immune system, as a result of which, these antibodies attack their own tissues. Specific antibodies can target specific tissues / organs, and cause damage. Examples of these are thyroiditis, rheumatoid arthritis, multiple sclerosis, etc, and of course myasthenia gravis.

Myasthenia is caused when autoimmunity produces antibodies which damage the junction between the nerve and the muscle. Due to this, the electrical potential or order is not carried from the nerve to the muscle, and the muscle does not contract as required, thus manifesting as weakness. In most cases, this affects predominantly the eye (causing drooping of eyelids and double vision / squint) and throat muscles (causing changed voice, nasal twang, and choking upon liquids). However, in many cases, hands, legs, trunk and respiratory muscles may also be involved.

Drugs like pyridostigmine can provide good relief in many patients. Steroids and other drugs suppressing immunity (and thereby autoimmunity) are also helpful. It is current consensus that patients with myasthenia gravis should undergo a surgery for removal of a small gland called "Thymus gland" just behind the sternum (breastbone), which improves the long term outcome.

In many cases, two or more autoimmune diseases affecting different systems may be present.

It is difficult to comment with the available information why your sister is having difficulty in walking and is bent to one side, but the possible explanation could be either truncal or body weakness due to myasthenia or some coexisting disease like rheumatoid arthritis.

She needs to be assessed by a qualified neurologist, and evaluated for these possibilities.