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NBME 23 Answers

nbme23/Block 4/Question#19

A 6-month-old male infant is brought to the ...

Regulatory T lymphocytes

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submitted by lfsuarez(114),

This patient presents with IPEX (immunodysregulation polyendocrinopathy enteropathy X-linked) which is a mutation of the FOXP3 gene which is a regulator for the Regulatory T cell lineage. It leads to the dysfunction of regulatory T-cells and the subsequent autoimunity.





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submitted by thotcandy(16),

IPEX: FOXP3 deficiency --> Regulatory T cell dysfunc --> autoimmunity

  • Enteropathy(diarrhea)

  • Endocrinopathy

  • Nail dystrophy

  • dermatitis (eczematous)

  • +/- other autoimmune conditions

  • associated with diabetes in male infants

Page 102 in FA19





So I didn't remember IPEX but I do know some basic inmuno and the stem sounded like many autoinmune manifestations, so logically a decrease in Treg lymphocytes (which are inmunosuppresive) seemed like the best answer.





Regulatory T cells Help maintain specific immune tolerance by suppressing CD4 + and CD8 + T-cell effector functions. Identified by expression of CD3, CD4, CD25, and FOXP3.

Activated regulatory T cells (Tregs) produce anti-inflammatory cytokines (eg, IL-10, TGF-β).

IPEX (Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked) syndrome— genetic deficiency of FOXP3 = autoimmunity. Characterized by enteropathy, endocrinopathy, nail dystrophy, dermatitis, and/or other autoimmune dermatologic conditions. Associated with diabetes in male infants.