Question

A 30-year-old woman presents with amenorrhea, oral candidiasis, and features of adrenal insufficiency. Laboratory findings show elevated FSH level as 27IU/L. Which gene mutation is most likely responsible for this condition?

• A. FMR
• B. AIRE
• C. 21-hydroxylase
• D. KAL

Hint:

Autoimmune Polyendocrine Syndromes (APS):
APS-1: Classic Triad = Chronic mucocutaneous Candidiasis + Hypoparathyroidism + Addison's disease. Caused by AIRE gene mutation.
APS-2: Classic Triad = Addison's disease + Autoimmune Thyroid disease + Type 1 Diabetes. Strongly associated with HLA-DR3/DR4.

Answer 1

The Correct Option is B

Concept:
A young adult female presents with a highly complex, textbook clinical triad: chronic mucocutaneous fungal infection (oral candidiasis), primary adrenal failure (adrenal insufficiency/Addison's disease), and primary ovarian insufficiency (evidenced by amenorrhea and a highly elevated FSH level).
The clinical task requires correctly identifying this specific syndromic constellation and linking it directly to the exact underlying genetic mutation responsible for the profound breakdown in central immune tolerance.
Explanation:
• The highly specific clinical triad of Chronic Mucocutaneous Candidiasis, Autoimmune Adrenal Insufficiency (Addison's disease), and Autoimmune Hypoparathyroidism (or primary hypogonadism, as seen in this patient with hypergonadotropic hypogonadism/amenorrhea) is the absolute, defining hallmark of Autoimmune Polyendocrine Syndrome Type 1 (APS-1).

• APS-1, which is also commonly referred to by the acronym APECED (Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy), is a rare, devastating autosomal recessive genetic disorder.

• It is caused entirely by deleterious loss-of-function mutations in the AIRE (Autoimmune Regulator) gene (Option B), which is located on chromosome 21.

• The AIRE gene is biologically critical for establishing central immune tolerance. It is predominantly expressed in the medullary epithelial cells of the thymus.

• Its primary function is to drive the ectopic transcription and expression of thousands of peripheral tissue-specific self-antigens (like insulin or adrenal enzymes) within the thymus.

• Developing T-cells are then exposed to these antigens. Any T-cell that binds too strongly to these self-antigens undergoes rapid negative selection (apoptosis).

• When the AIRE gene is mutated, this massive ectopic antigen presentation fails. Consequently, highly auto-reactive T-cells escape negative selection, enter the peripheral circulation, and mount devastating, targeted autoimmune attacks against multiple endocrine glands (most notably the adrenals, parathyroids, and gonads).

• The FMR1 gene mutation (Option A) causes Fragile X syndrome (which can cause premature ovarian failure, but lacks the candidiasis and adrenal failure).

• 21-hydroxylase deficiency (Option C) is the most common cause of Congenital Adrenal Hyperplasia (CAH), causing virilization and adrenal insufficiency, not this broad autoimmune triad.

• KAL1 mutation (Option D) causes Kallmann syndrome, characterized by hypogonadotropic hypogonadism (low FSH/LH) and anosmia.
Final Answer:
The classic triad of candidiasis, adrenal insufficiency, and hypogonadism indicates Autoimmune Polyendocrine Syndrome Type 1, which is caused by a mutation in the AIRE gene.