Head and Neck
Evaluation of an infant reveals hypocalcemia due to a lack of parathyroid hormone. On x-ray, the thymic shadow is absent. Which of the following embryonic structures is involved (AIIMS Nov 2013)
|A||Third pharyngeal cleft|
|B||Fourth pharyngeal cleft|
|C||Third pharyngeal pouch|
|D||Fourth pharyngeal pouch|
Since thymus is missing, appropriate answer would be third pharyngeal pouch (PP3 -TIP). This patient has got DiGeorge syndrome.
DiGeorge syndrome causes migration defects of neural crest-derived tissues, particularly affecting development of the third and fourth Branchial pouch (pharyngeal pouches)