Hello and welcome to the Zero to Finals podcast.

My name is Tom and in this episode I'm going to be talking to you about T-cell disorders.

And if you want to follow along with written notes on this topic,

you can follow along at zero-definals.com slash T-cell disorders

or in the immunology section of the Zero-definals pediatrics book.

So let's get straight into it.

Conditions that cause abnormal or absent T-cells will result in immunodeficiency.

And we're going to discuss some of these specific disorders in detail.

Firstly, let's start with DeGeorge Syndrome.

DeGeorge Syndrome, which is also called 22-Q11.2 deletion syndrome,

results from a micro-deletion in a portion of chromosome 22 that leads to a developmental defect

in the third pharyngeal pouch and the third

brankeal cleft. One of the consequences of this is incomplete development of the thymus gland.

An underdeveloped thymus gland results in an inability to create functional T cells. Remember the thymus gland is

essential for the creation of T cells. The features of DeGeorge syndrome can be remembered with

the catch-22 pneumonic. C stands for congenital heart disease. A stands for abnormal facies referring to the characteristic

facial appearance. T stands for thymus gland incompletely developed. C stands for clef palate.

H stands for hypothyroidism and resulting hypo-calcemia. And 22 stands for hypoparthiroidism and resulting hypo-calcemia, and 22 stands for the 22nd

chromosome that's affected. Next let's talk about purine nucleoside phosphorylase deficiency.

A deficiency of purine nucleoside phosphorylase or PNP is an autosomal recessive condition.

Purine nucleoside phosphorylase is an enzyme that helps break down purines. Without this enzyme,

a metabolite called DGTP builds up.

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