A 54-year-old man with no significant past medical history comes to the physician with complaints of fatigue over the last 2 months. He tried to exercise a few times but tired easily. The patient is so exhausted by the end of the day that he starts "to see double." An upper respiratory illness 2 weeks ago left him extremely fatigued. He has also noticed occasional trouble swallowing and frequent coughing while drinking. The patient has no fever, cough, chills, weight loss, or night sweats. He does not use tobacco, alcohol, or illicit drugs. He has been married for 26 years and has no HIV risk factors.
His blood pressure is 122/68 mm Hg, and pulse is 82/min. His BMI is 25 kg/m². There is no scleral icterus or conjunctival pallor on inspection. Visual field examination is within normal limits. No enlarged lymph nodes are palpated. Lungs are clear to auscultation. There is no palpable spleen tip.
After initial evaluation, CT scan of the chest is performed (see below) .

Which of the following is the most likely diagnosis?

Question

A 54-year-old man with no significant past medical history comes to the physician with complaints of fatigue over the last 2 months. He tried to exercise a few times but tired easily. The patient is so exhausted by the end of the day that he starts "to see double." An upper respiratory illness 2 weeks ago left him extremely fatigued. He has also noticed occasional trouble swallowing and frequent coughing while drinking. The patient has no fever, cough, chills, weight loss, or night sweats. He does not use tobacco, alcohol, or illicit drugs. He has been married for 26 years and has no HIV risk factors.
His blood pressure is 122/68 mm Hg, and pulse is 82/min. His BMI is 25 kg/m². There is no scleral icterus or conjunctival pallor on inspection. Visual field examination is within normal limits. No enlarged lymph nodes are palpated. Lungs are clear to auscultation. There is no palpable spleen tip.
After initial evaluation, CT scan of the chest is performed (see below) .

Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

This patient's fatigue, diplopia, and dysphagia, combined with the anterior mediastinal mass on chest CT, suggest myasthenia gravis (MG) and thymoma. Nearly 10-15% of MG patients develop thymoma, and 50-70% of thymoma patients will have MG symptoms. MG is due to autoantibodies blocking acetylcholine receptors. Patients have fluctuating weakness that classically worsens with exercise, physical or emotional stress, or infection, and improves with rest. Patients may also have ocular symptoms (eg, diplopia, ptosis), dysarthria, dysphagia, inability to work with arms raised over the head, or gait disturbance. Anterior mediastinal tumors are most commonly due to the 4Ts: Thymoma (most common cause) and other thymus tumorsTeratoma and other germ cell tumorsThyroid tumors (or goiter)"Terrible" lymphoma (also located in the middle or posterior mediastinum) Thymoma (most common cause) and other thymus tumors Teratoma and other germ cell tumors Thyroid tumors (or goiter) "Terrible" lymphoma (also located in the middle or posterior mediastinum) Surgery with clinical staging is the preferred treatment approach for thymomas and thymic carcinomas. Thymectomy is generally suggested for patients < age 60 with generalized MG. (Choice A) Lymphomas are the second most common cause of anterior mediastinal mass after thymoma. They are difficult to distinguish from thymomas on CT scan. However, lymphomas usually present with systemic B symptoms (eg, fever, night sweats, and weight loss) and extranodal involvement. (Choice B) Tuberculosis can sometimes cause an isolated mediastinal mass. This patient's absence of parenchymal lung lesions, symptoms, or exposure to tuberculosis makes this less likely. (Choice C) Lambert-Eaton myasthenic syndrome (LEMS) is a paraneoplastic syndrome associated with small cell lung cancer that usually presents with slowly progressive proximal muscle weakness, decreased deep-tendon reflexes, dry mouth, and erectile dysfunction. Vigorous and brief muscle activation usually improves recovery of deep-tendon reflexes and muscle strength. Ocular symptoms are rare in LEMS. (Choice D) About 70-90% of patients with substernal goiter also have a visible goiter. Patients can have subclinical hyperthyroidism, overt hyperthyroidism, or be euthyroid on presentation. However, they are usually not hypothyroid. This patient's presenting symptoms are more suggestive of MG. Educational objective: Thymoma is the most common cause of an anterior mediastinal mass. It often occurs concomitantly with myasthenia gravis (MG). Thymectomy is suggested for patients < age 60 with generalized MG. Other anterior mediastinal masses include teratoma, lymphoma, and thyroid tumors. __________ References: Clinical management of thymoma patients. (http://www.ncbi.nlm.nih.gov/pubmed/18514127) Thymoma, myasthenia gravis, and other paraneoplastic syndromes. (http://www.ncbi.nlm.nih.gov/pubmed/18514130)

A 54-Year-Old Man with No Significant Past Medical History Comes