DiGeorge syndrome is due to:

 # DiGeorge syndrome is due to:

A. Congenital thymic aplasia

B. Deficiency of complement factors

C. Inborn error of metabolism

D. Chromosomal anomaly

The correct answer is D. Chromosomal anomaly.

The correct answer is:

D. Chromosomal anomaly

Explanation: DiGeorge syndrome is caused by a chromosomal anomaly, specifically a 22q11.2 deletion. 

This deletion leads to developmental defects in the pharyngeal pouches, resulting in: Congenital thymic aplasia or hypoplasia (leading to T-cell deficiency).

Parathyroid hypoplasia (causing hypocalcemia).

Cardiac defects (e.g., Tetralogy of Fallot, interrupted aortic arch).

Facial dysmorphisms.

Other options explained:

A. Congenital thymic aplasia: While thymic aplasia is a feature of DiGeorge syndrome, it is secondary to the chromosomal deletion.

B. Deficiency of complement factors: Seen in complement pathway defects, not in DiGeorge syndrome.

C. Inborn error of metabolism: DiGeorge syndrome is not related to metabolic enzyme deficiencies.