A 45 year old woman presents complaining of weakness that comes and goes. It's worse in the evening and after she plays tennis. She also complains that her tennis game is being affected because sometimes things "look funny." You suspect she's seeing double. On exam, you notice ptosis.CXRs are shown above. You recognize the abnormality and remember the differential with the "T mnemonic."
Challenge: What's your diagnosis?
Related Questions:
1. What's the finding on the CXRs?
2. What's the T mnemonic? (or what is the differential for the abnormality?)
3. How does that relate to the patient's presentation?
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2 comments:
TERATOMA!!!
Just kidding :P
Diagnosis: Thymoma with myasthenia gravis
1. There is an anterior mediastinal mass on the CXRs.
2. The 4 T's is a mnemonic for diagnosing anterior mediastinal masses. They are: Thymoma, Teratoma, Thyroid tumor, and Terrible lymphoma. The fifth T should be Terrible mnemonic!
3. The patient's weakness comes from the myasthenia gravis, which is an autoimmune disease involving the development of antibodies against nicotinic acetylcholine receptors at the neuromuscular junction. The diplopia and ptosis come from weakness of the extraocular muscles and the levator palpebrae superioris muscles.
Terrible T’s
The finding on the CXR is an anterior mediastinal mass. The “T” DDX is: Thymoma, Thyroid, Teratoma, Terrible lymphoma, (Testicular tumor, and paraThyroid tumor). This is the presentation of a thymoma.
A thymoma is a neoplasm of epithelial cells of the thymus. The epidemiology is age 30-50, males=females. Many patients are asymptomatic and this is found incidentally. If the tumor is large and impinges on nearby structures, the patient can present with chest pain, shortness of breath, cough, phrenic nerve palsy, superior vena cava syndrome, fever, weight loss, or night sweats. Treatment is surgery with chemotherapy or radiation therapy.
Thymomas are associated with a paraneoplastic syndrome causing myasthenia gravis (present in 35% patients at diagnosis). (They are also associated with red cell aplasia and hypergammaglobulinemia). Myasthenia gravis is characterized by autoantibodies against the acetylcholine receptor. This causes the presentation described here. The pathogenesis is unknown.
Sources: Washington University in St. Louis (www.neuro.wustl.edu), UpToDate.
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