Why are thymectomies not done on patients with multiple sclerosis like with myasthenia gravis?

See answer below. Myasthenia gravis is an autoimmune disorder, driven by imbalances of immune cell subtypes that is distinctly different from that in ms. Removing the thymus in myasthenia gravis can reduce the number of immune cells in that disorder, and help reduce disease activity. The same would not be expected for ms.
Cause of autoimmune. Thymectomy has been shown to be a helpful treatment for some people with myasthenia gravis, but no other autoimmune diseases. This includes multiple sclerosis. In this case, the cause of the disease is not known to be linked to the action of B lymphocytes, which are modulated by cells that are produced by the thymus. Myasthenia is also linked to thymus hyperplasia and thymoma, MS is not.
Different diseases. Myasthenia gravis affects neuromuscular junction in the periphery and MS affects nerve coverings in the central nervous system. The immune process is completely different and distinct in each disorder.

Related Questions

Are multiple sclerosis and myasthenia gravis conditions of the neuroglia?

Not likely. Both conditions are autoimmune disorders, as ms attacks myelin nerve coverings in brain and spinal cord, but mg damages the peripheral junction receptors between nerve and muscle. Some evidence is arising that the CNS might involve astrocytes in ms, but no such data is known in mg. Treatments are very different from one disease to the other. Read more...
Neither of them. Neither of these conditions is a condition of the neuroglia. To some extent, glial cells are involved in the repair of damage that occurs in MS. Myasthenia is a condition that occurs at the junction of the nerve and muscle, no glia cells are present there. Read more...

How does the pathology of multiple sclerosis compare to that of myasthenia gravis?

Both autoimmune, Mg is peripheral, ms central. Myasthenia is a disease of the neuromuscular junction, and causes weakness on progressive exertion, or drooping of eyelids or fluctuating double vision. Ms is a disease of brain and spinal cord, and causes weakness and fatigue of a fairly constant type. Loss of vision, bowel and bladder problems, loss of coordination and balance can be seen. Read more...
They are different. Myasthenia gravis and multiple sclerosis are entirely different illnesses. Their symptoms, diagnosis, treatment and pathology are different. In MG, there are antibodies that block the neuromuscular junction. This normally causes weakness and fatigue. In MS, there are lesions of the brain, spinal cord and optic nerves that affect various neurological functions. Read more...

Why would a thymectomy not be done on an otherwise healthy 18 yr old suffering with generalised myasthenia gravis? Thank you for taking time to reply

Thymectomy is option. Thymectomy is a good option in the treatment of myasthenia gravis. It can result in remission of symptoms in many patients. Patients with just ocular involvement often do not need surgery, but otherwise unless there is a contraindications for surgery thymectomy would be a good option. Read more...
Afraid. Many referring physicians will not send patients for thymectomy out of fear of procedure. Modern, well trained thoracic surgeons can perform thymectomy by vats or robotic technique on appropriate candidates. Sternotomy is not routinely required for thymectomy. http://goo.gl/3xxmd. Read more...