All are seen in DiGeorge syndrome Except
**Core Concept**
DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a rare genetic disorder characterized by thymic hypoplasia, parathyroid gland aplasia or hypoplasia, and characteristic facial features. It is caused by a deletion of a segment of chromosome 22q11.2, leading to a deficiency of the enzyme 22-hydroxylase, which is necessary for the production of cortisol and aldosterone. This results in hypocalcemia, hypoparathyroidism, and increased susceptibility to infections due to immunodeficiency.
**Why the Correct Answer is Right**
DiGeorge syndrome is characterized by a triad of clinical features: congenital heart defects, cleft palate, and hypocalcemia due to hypoparathyroidism. The parathyroid glands are underdeveloped or absent, leading to decreased production of parathyroid hormone (PTH), which regulates calcium levels in the blood. The thymus is also underdeveloped, resulting in immunodeficiency and increased susceptibility to infections. The facial features of DiGeorge syndrome include a pointed chin, low-set ears, and a cleft palate.
**Why Each Wrong Option is Incorrect**
**Option A:** Not a characteristic feature of DiGeorge syndrome. While patients may have a range of physical abnormalities, this is not a hallmark of the condition.
**Option B:** Actually a characteristic feature of DiGeorge syndrome. The facial abnormalities are a key diagnostic criterion for the condition.
**Option C:** Not a characteristic feature of DiGeorge syndrome. While patients may have a range of physical abnormalities, this is not a hallmark of the condition.
**Clinical Pearl / High-Yield Fact**
One of the most important clinical features of DiGeorge syndrome is the association with congenital heart defects, particularly tetralogy of Fallot and truncus arteriosus. This highlights the importance of a thorough cardiac evaluation in patients with suspected DiGeorge syndrome.
**Correct Answer: B. Cleft palate is a characteristic feature of DiGeorge syndrome.**