A 32-year-old woman complains of weakness in her hands and "heaviness" in her eyelids at the end of each day. Chest imaging shows an anterior mediastinal mass. The organ from which this mass most likely originated shares its embryologic origin with:

Question

A 32-year-old woman complains of weakness in her hands and "heaviness" in her eyelids at the end of each day.  Chest imaging shows an anterior mediastinal mass.  The organ from which this mass most likely originated shares its embryologic origin with:

Quizplus · Accepted Answer

Myasthenia gravis causes muscle weakness, with the extraocular muscles most commonly affected. Patients often experience ptosis and diplopia. The muscle weakness worsens with activity, and patients often note that their symptoms are worse at the end of the day. The majority of patients with myasthenia gravis are found to have a thymoma or thymic hyperplasia. 11ec160b_3753_4d28_9249_b11ba7acf3dd_MD0001_00 The thymus is derived from the third pharyngeal pouch, as are the inferior parathyroid glands. The table below lists the derivatives of the pharyngeal pouches, grooves and membranes: 11ec160b_3753_4d29_9249_43171b6924c5_MD0001_00 (Choice A) The floor of the foregut gives rise to the thyroid diverticulum. The thyroid diverticulum migrates caudally to the neck, but remains attached to the floor of the mouth by the thyroglossal duct. (Choice B) The superior parathyroid glands and ultimobranchial body are formed from the 4^th pharyngeal pouch. (Choice D) Most of the laryngeal cartilages develop from the 4^th and 6^th pharyngeal arches. (Choice E) The palatine tonsils are derived from the second pharyngeal pouches. Educational Objective: Myasthenia gravis is associated with abnormalities of the thymus (e.g. thymoma, thymic hyperplasia). The thymus and inferior parathyroid glands arise from the 3rd pharyngeal pouch.

A 32-Year-Old Woman Complains of Weakness in Her Hands and "Heaviness