All are true regarding subacute combined immunodeficiency except:
**Core Concept**
Subacute combined immunodeficiency (SCID) is a group of rare genetic disorders characterized by impaired cellular and humoral immunity, leading to recurrent infections, autoimmune phenomena, and malignancies. It results from mutations in various genes responsible for the development and function of T cells and B cells, including those involved in adenosine deaminase (ADA) and interleukin-7 receptor (IL7R) signaling pathways.
**Why the Correct Answer is Right**
The correct answer will be identified by eliminating the true statements regarding SCID. SCID is indeed characterized by impaired T cell function, resulting from mutations in genes such as **CD3ζ** (not listed), **IL7R**, and **RAG1/2**, which are essential for T cell development and function. SCID patients also exhibit increased susceptibility to opportunistic infections, autoimmune phenomena, and malignancies. The ADA enzyme deficiency is a specific type of SCID, but not the only form.
**Why Each Wrong Option is Incorrect**
**Option A:** This is a true statement regarding SCID. Patients with SCID indeed exhibit impaired T cell function, which is a hallmark of the disease.
**Option B:** This is a true statement regarding SCID. SCID patients are indeed susceptible to opportunistic infections, which can be life-threatening.
**Option C:** This is a true statement regarding SCID. SCID patients do exhibit increased susceptibility to autoimmune phenomena, which can manifest as various autoimmune disorders.
**Clinical Pearl / High-Yield Fact**
It is essential to recognize that SCID is a clinical diagnosis, and laboratory tests, such as flow cytometry and genetic analysis, are used to confirm the diagnosis. Early recognition and treatment of SCID can significantly improve patient outcomes.
**Correct Answer: None**