Immunology · Year 2 · from Immunology
Case 1: IPEX Syndrome (Regulatory T Cell Deficiency)
Patient Demographics
- Age: 8 weeks old
- Sex: Male
- Ethnicity: Caucasian
Chief Complaint
Severe diarrhea, skin rash, and failure to thrive
History of Present Illness
An 8-week-old male infant presents with profuse watery diarrhea since 2 weeks of age, not responsive to formula changes or hydrolyzed formulas. He has developed an extensive eczematous rash on his face, trunk, and extremities. His parents note he feeds poorly and has not gained weight since birth. He was hospitalized at 4 weeks for hyperglycemia requiring insulin (blood glucose 450 mg/dL).
Past Medical History
- Neonatal diabetes diagnosed at 4 weeks (currently on insulin)
- Severe diarrhea since 2 weeks of age
- Eczematous rash since 3 weeks of age
- Weight loss
Birth History
- Full-term vaginal delivery
- Birth weight: 3.2 kg (40th percentile)
- Current weight: 3.0 kg (<3rd percentile)
Family History
- Maternal uncle died at 3 months of age from "diarrhea and infection"
- No other family history of autoimmune disease
Physical Examination
- General: Wasted, ill-appearing infant
- Vital Signs: T 37.5C, HR 160, RR 40
- Growth: Weight 3.0 kg (<3rd percentile), down from birth weight
- Skin: Diffuse erythematous, scaly, eczematous rash on face, trunk, extremities; areas of weeping
- HEENT: Normal
- Abdomen: Distended, hyperactive bowel sounds
- Lymphatics: Generalized lymphadenopathy
Laboratory Workup
| Test | Result | Reference Range |
|---|---|---|
| WBC | 25,000/uL | 6,000-17,500/uL |
| Eosinophils | 15% | 0-4% |
| Hemoglobin | 8.5 g/dL | 10-14 g/dL |
| Platelets | 55,000/uL | 150,000-400,000/uL |
| IgE | 2500 IU/mL | <100 IU/mL |
| CD4+CD25+FOXP3+ Tregs | <1% of CD4 T cells | 5-10% |
| Glucose | 380 mg/dL | 60-100 mg/dL |
| C-peptide | <0.1 ng/mL | 0.5-2.0 ng/mL |
| Anti-GAD65 antibodies | Positive | Negative |
| Anti-enterocyte antibodies | Positive | Negative |
| FOXP3 gene | Hemizygous mutation | Wild type |
| Intestinal biopsy | Severe villous atrophy with lymphocytic infiltration | Normal villi |
Clinical Image
Image showing severe eczematous dermatitis similar to that seen in IPEX syndrome. Image source: Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Atopic_dermatitis_child.JPG). Licensed under CC BY 2.0.
Diagnosis
IPEX Syndrome (Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked) due to FOXP3 mutation causing regulatory T cell deficiency.
Discussion
IPEX syndrome results from mutations in FOXP3, the master transcription factor required for regulatory T cell (Treg) development and function. Without functional Tregs, uncontrolled autoimmunity develops against multiple organs:
Classic triad (usually presents in first months of life):
- Enteropathy: Severe, intractable diarrhea from autoimmune enteropathy; villous atrophy on biopsy
- Endocrinopathy: Type 1 diabetes (very early onset), autoimmune thyroiditis
- Dermatitis: Severe eczema or psoriasiform rash
Additional features:
- Autoimmune cytopenias (AIHA, ITP, autoimmune neutropenia)
- Elevated IgE and eosinophilia
- Food allergies
- Recurrent infections (from immunosuppressive treatment)
Why is this X-linked?
- FOXP3 gene is located on the X chromosome
- Males with mutation have no functional FOXP3
- Carrier females are typically asymptomatic (random X-inactivation)
Treatment
- Supportive care: TPN for nutritional support, insulin for diabetes
- Immunosuppression: Sirolimus (rapamycin) - may be preferred as it spares Treg development; cyclosporine, tacrolimus, or steroids also used
- Hematopoietic stem cell transplantation: Only curative option; should be performed early before irreversible organ damage
- Manage specific manifestations: Topical steroids for skin, diabetes management
Prognosis: Without HSCT, most patients die in the first 1-2 years of life from infections or metabolic complications.