All are false of Bruton’s Agammaglobulinemic except
**Core Concept**
Bruton's Agammaglobulinemia is a genetic disorder characterized by a deficiency in B cells, leading to impaired antibody production. This results from mutations in the BTK gene, which encodes the tyrosine kinase enzyme Bruton's tyrosine kinase (BTK). BTK plays a crucial role in signaling pathways that regulate B-cell development and activation.
**Why the Correct Answer is Right**
The correct answer is related to the fact that patients with Bruton's Agammaglobulinemia have impaired B-cell function, but they do have some residual B-cell activity. This residual activity is due to the presence of some BTK activity, which is sufficient to allow for the development of some B cells, but not enough to support antibody production. Additionally, patients with Bruton's Agammaglobulinemia have normal T-cell function and normal numbers of T cells.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Bruton's Agammaglobulinemia is characterized by a deficiency in B cells, not T cells.
**Option B:** This option is incorrect because Bruton's Agammaglobulinemia is not caused by a deficiency in the T-cell receptor.
**Option C:** This option is incorrect because Bruton's Agammaglobulinemia is caused by a mutation in the BTK gene, not the CD40 ligand gene.
**Clinical Pearl / High-Yield Fact**
Bruton's Agammaglobulinemia is the first identified genetic disorder of the immune system and is often referred to as the first "primary immunodeficiency disease". It is an X-linked recessive disorder, meaning it predominantly affects males.
**Correct Answer:** D