Adenosine deaminase (enzyme) deficiency is associated with
**Core Concept**
Adenosine deaminase (ADA) is a crucial enzyme involved in the breakdown of adenosine and deoxyadenosine. Its deficiency leads to an accumulation of toxic metabolites, resulting in severe immunodeficiency and cellular damage.
**Why the Correct Answer is Right**
The correct answer is related to Severe Combined Immunodeficiency (SCID). ADA deficiency is a rare genetic disorder that affects the function of immune cells, including T and B lymphocytes. This is due to the accumulation of toxic metabolites such as deoxyadenosine triphosphate (dATP), which inhibits the enzyme ribonucleotide reductase, thereby preventing the synthesis of DNA and leading to cell death. The lack of functional immune cells makes individuals with ADA deficiency highly susceptible to infections.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because ADA deficiency is not primarily associated with Cystic Fibrosis. While both conditions are genetic disorders, they are distinct and have different underlying mechanisms.
**Option B:** This option is incorrect because ADA deficiency is not directly linked to G6PD deficiency. Although both conditions can cause hemolysis, they are unrelated in terms of pathophysiology.
**Option C:** This option is incorrect because ADA deficiency is not primarily associated with Pernicious Anemia. While both conditions can cause immunodeficiency, they are distinct and have different underlying mechanisms.
**Clinical Pearl / High-Yield Fact**
ADA deficiency is a rare but severe form of SCID, and early diagnosis and treatment are crucial to prevent life-threatening infections and improve survival rates.
**Correct Answer:** D. Severe Combined Immunodeficiency (SCID)