Hi, this is Tom, and in this episode I'm going to be going through B-cell and immunoglobulin

disorders. And you can find notes at 0.0.0.5 and in the 0.0-2-finals pediatrics book,

and you can find flashcards and questions at members.0.0.5.com.

So let's jump straight in.

B cells are responsible for producing antibodies, which is an essential component of the adaptive

immune system.

Abnormal B cells lead to reduced immunoglobulins or antibodies, and this is called hypogamaglobulinemia.

B-cell disorders lead to susceptibility to infections, particularly respiratory tract infections.

Patients are notably susceptible to infections caused by encapsulated bacteria. For example, Streptococcus

pneumonia, imophilus influenza and nyseria meningitis. Let's talk about selective IGA deficiency.

Selective IGA deficiency is the most common immunoglobulin deficiency.

Patients have low IGA levels and normal IgG and IgM levels. IGA is present in secretions of

the mucus membranes such as saliva, the respiratory tract,

gastrointestinal tract, tears and sweat. IGA protects the mucus membranes against infection.

Selective IGA deficiency causes mild immunodeficiency.

Patients are often asymptomatic and never diagnosed.

They may have a tendency to recurrent infections, for example recurrent respiratory infections and also autoimmune conditions.

At a top tip for you, IGA deficiency is relevant when you're testing for suspected celiac

disease.

The blood tests for celiac disease look for the IGA version of anti-TTG or anti-EMA antibodies.

When testing these antibodies, it's also important to measure the total immunoglobulin A levels.

If the total IGA level is low due to IGA deficiency, the celiac test will be falsely negative.

...