Thymic hypoplasia is seen in -

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.