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Wednesday, January 07, 2009

Thymoma commonly presents with Myasthenia Gravis

Question 89
Thymoma commonly presents with
a.       Myasthenia Gravis
b.      ??
c.       ??
d.       ??
Answer
a. Myasthenia Gravis
Reference
Harrison 16th Edition Page
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Discussion
Myasthenia gravis (MG) is an acquired autoimmune disorder characterized clinically by weakness of skeletal muscles and fatigability on exertion. Thomas Willis reported the first clinical description in 1672.
The antibodies in MG are directed toward the acetylcholine receptor (AChR) at the neuromuscular junction (NMJ) of skeletal muscles.
Explanation
The exact mechanism of loss of immunologic tolerance to AChR, a self antigen, is not understood. MG can be considered a B cell–mediated disease, as antibodies (a B cell product) against AChR are responsible for the disease. However, the importance of T cells in pathogenesis of MG is becoming increasingly apparent. The thymus is the central organ in T cell–mediated immunity, and thymic abnormalities such as thymic hyperplasia or thymoma are well recognized in myasthenic patients.
Comments
Since this question is often repeated, every one attempted it in a jiffy that they could not even recollect the other choices afterwards
Tips
Ä     MG is idiopathic in most patients.
Ä     Penicillamine is known to induce various autoimmune disorders, including MG.

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