This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immune Deficiency Diseases, Subject name: Pathology
Thymic hypoplasia is seen in - 
Select and explain. 
A. Wiskott-Aldrich syndrome, B. Digeorge syndrome, C. IgA deficiency, D. Agammaglobulinemia
B: Digeorge syndrome
Answer: B: Digeorge syndrome 
Explanation: Ans. is 'b- i.e., Digeorge syndrome o In Digeorge syndrom e, there is absen ce of norm a l thymus.Digeorge syndromeo Digeorge syndrome is an example of a T cell deficiency that results from failure of development of the third and fourth pharyngeal pouches.Clinical featureso Enhanced susceptibility to viral, fungal (mucocutaneous candidiasis) and bacterial infections,o Facial abnormalities : Hypertelorism, abnormal ears, short philtrum and micrognathia,o Hypocalcemic tetany due to failure of parathyroid development,o Congenital heart diseases eg fallot's tetralogy,o Absence of a normal thymus.o Serum immunoglobulin concentration are frequently normal, but antibody responses, particularly of IgG and IgA isotvpes, are usually impaired,o T cell levels are reduced (not total absenceo B cell levels are normal.