# Clinical Cases: T Cells and Cell-Mediated Immunity

## 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
![Eczematous dermatitis](https://upload.wikimedia.org/wikipedia/commons/thumb/d/de/Atopic_dermatitis_child.JPG/220px-Atopic_dermatitis_child.JPG)

*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):**
1. **Enteropathy:** Severe, intractable diarrhea from autoimmune enteropathy; villous atrophy on biopsy
2. **Endocrinopathy:** Type 1 diabetes (very early onset), autoimmune thyroiditis
3. **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
1. **Supportive care:** TPN for nutritional support, insulin for diabetes
2. **Immunosuppression:** Sirolimus (rapamycin) - may be preferred as it spares Treg development; cyclosporine, tacrolimus, or steroids also used
3. **Hematopoietic stem cell transplantation:** Only curative option; should be performed early before irreversible organ damage
4. **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.

---

## Case 2: Job Syndrome (Hyper-IgE Syndrome - STAT3 Deficiency)

### Patient Demographics
- **Age:** 12 years old
- **Sex:** Female
- **Ethnicity:** Caucasian

### Chief Complaint
Recurrent skin abscesses and pneumonia

### History of Present Illness
A 12-year-old girl is referred for evaluation of recurrent Staphylococcus aureus skin abscesses and two episodes of pneumonia. Her mother notes that the skin abscesses are unusual - they are large but do not seem very red or painful ("cold abscesses"). She has had eczema since infancy. Her first pneumonia at age 8 resulted in a residual lung cyst that is still present.

### Past Medical History
- Eczema since infancy (severe, requiring topical steroids)
- Recurrent skin abscesses since age 2 (Staph aureus cultured multiple times)
- Pneumonia at ages 8 and 11 (first caused pneumatocele formation)
- Chronic mucocutaneous candidiasis (oral thrush, onychomycosis)
- Retained primary teeth (required extraction of 6 baby teeth)
- Multiple fractures from minimal trauma (arm age 7, leg age 10)

### Family History
- No family history of similar symptoms
- Parents are healthy

### Physical Examination
- **General:** Girl with coarse facial features
- **Vital Signs:** Normal
- **HEENT:** Coarse facies with broad nasal bridge, wide-set eyes, prominent forehead; oral thrush present
- **Skin:** Multiple hyperpigmented scars from healed abscesses; one large "cold" abscess on thigh - fluctuant but minimal erythema or warmth
- **Lungs:** Clear, but imaging shows right lower lobe pneumatocele
- **MSK:** Hyperextensible joints, mild scoliosis
- **Teeth:** Several retained primary teeth

### Laboratory Workup
| Test | Result | Reference Range |
|------|--------|-----------------|
| WBC | 10,500/uL | 4,500-13,500/uL |
| Eosinophils | 18% | 0-4% |
| **IgE** | **8,500 IU/mL** | <100 IU/mL |
| IgG | Normal | -- |
| IgA | Normal | -- |
| IgM | Normal | -- |
| Th17 cells (% of CD4) | 0.2% | 1-2% |
| **STAT3 gene** | **Dominant negative mutation** | Wild type |

### Clinical Image
![Pneumatocele on CT](https://upload.wikimedia.org/wikipedia/commons/thumb/1/1d/Pneumatocele1.PNG/220px-Pneumatocele1.PNG)

*Image showing pneumatocele (lung cyst) formation, a characteristic complication of pneumonia in Hyper-IgE syndrome. Image source: Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Pneumatocele1.PNG). Licensed under CC BY-SA 3.0.*

### Diagnosis
**Autosomal Dominant Hyper-IgE Syndrome (Job Syndrome)** due to STAT3 dominant negative mutation.

### Discussion
Job syndrome (AD-HIES) results from dominant negative mutations in STAT3, causing a multisystem disorder with both immunological and connective tissue manifestations:

**Immunological features:**
- **Markedly elevated IgE** (often >2000 IU/mL)
- **"Cold" staphylococcal abscesses:** Lack the typical inflammatory signs due to impaired neutrophil chemotaxis
- **Recurrent pneumonia with pneumatocele formation:** Characteristic; cysts persist and can become superinfected with Aspergillus or Pseudomonas
- **Chronic mucocutaneous candidiasis:** Due to impaired Th17 responses

**Why is Th17 important here?**
- STAT3 is required for Th17 differentiation
- Th17 cells produce IL-17, which recruits neutrophils and induces epithelial antimicrobial peptides
- Impaired Th17 function leads to susceptibility to Staph aureus and Candida at mucocutaneous surfaces

**Non-immunological features (distinguish from other causes of elevated IgE):**
- Coarse facies
- Retained primary teeth (failure to resorb roots)
- Hyperextensible joints
- Pathological fractures (osteopenia)
- Scoliosis
- Coronary artery aneurysms (rare)

### Treatment
1. **Prophylactic antibiotics:** TMP-SMX for Staph aureus prevention
2. **Antifungal prophylaxis:** For mucocutaneous candidiasis
3. **Aggressive treatment of infections:** Including drainage of abscesses
4. **Pneumatocele management:** Surveillance for superinfection; may require surgical resection
5. **Skin care:** Aggressive eczema management
6. **Bone health:** Calcium, vitamin D supplementation
7. **Dental care:** Monitor for and extract retained primary teeth
8. **No established definitive therapy:** HSCT has been attempted but results are mixed

---

## Case 3: Autoimmune Polyendocrinopathy Syndrome Type 1 (APS-1/APECED)

### Patient Demographics
- **Age:** 9 years old
- **Sex:** Female
- **Ethnicity:** Finnish descent

### Chief Complaint
Muscle cramps and recurrent oral thrush

### History of Present Illness
A 9-year-old girl of Finnish descent presents with hand and foot muscle cramping and tingling for 2 weeks. She has a history of chronic oral thrush since age 3 that has been difficult to control. Her parents note that she has also developed patchy hair loss over the past year.

### Past Medical History
- Chronic mucocutaneous candidiasis since age 3 (oral, esophageal, nail involvement)
- Alopecia areata starting at age 8
- Dental enamel hypoplasia (noted by dentist)

### Family History
- Parents are first cousins (consanguineous)
- No known family history of autoimmune disease

### Physical Examination
- **General:** Well-appearing girl
- **Vital Signs:** Normal
- **HEENT:** White plaques on tongue and buccal mucosa (oral candidiasis); dental enamel defects
- **Skin:** Patches of alopecia on scalp (alopecia areata pattern)
- **Nails:** Thickened, dystrophic fingernails (onychomycosis)
- **Neurological:** Positive Chvostek sign (facial muscle twitch with tapping over facial nerve); positive Trousseau sign (carpopedal spasm with BP cuff inflation)

### Laboratory Workup
| Test | Result | Reference Range |
|------|--------|-----------------|
| Calcium | 6.2 mg/dL | 8.5-10.5 mg/dL |
| Phosphorus | 7.5 mg/dL | 3.0-5.5 mg/dL |
| PTH | 8 pg/mL | 15-65 pg/mL |
| Magnesium | Normal | -- |
| Cortisol (AM) | Normal | -- |
| ACTH stimulation test | Normal | -- |
| Anti-IFN-omega antibodies | Positive | Negative |
| Anti-IL-17A antibodies | Positive | Negative |
| Anti-IL-22 antibodies | Positive | Negative |
| **AIRE gene** | **Homozygous mutation** | Wild type |

### Clinical Image
![Oral Candidiasis](https://upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Oral_thrush_adult.jpg/220px-Oral_thrush_adult.jpg)

*Image showing chronic oral candidiasis, one of the characteristic features of APECED/APS-1. Image source: Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Oral_thrush_adult.jpg). Licensed under CC BY-SA 4.0.*

### Diagnosis
**Autoimmune Polyendocrine Syndrome Type 1 (APS-1)/APECED** (Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy) due to AIRE gene mutation.

### Discussion
APS-1/APECED is caused by autosomal recessive mutations in AIRE (Autoimmune Regulator), a transcription factor critical for central T cell tolerance:

**AIRE's normal function:**
- Expressed in medullary thymic epithelial cells
- Drives expression of tissue-restricted antigens (insulin, thyroglobulin, etc.) in the thymus
- Allows deletion of T cells reactive against these peripheral tissue antigens
- Without AIRE, autoreactive T cells escape to the periphery

**Classic diagnostic triad (2 of 3 required):**
1. **Chronic mucocutaneous candidiasis (CMC)** - usually first manifestation, often by age 5
2. **Hypoparathyroidism** - causes hypocalcemia (present in this case)
3. **Adrenal insufficiency** - often develops later

**Additional manifestations:**
- Ectodermal dystrophy: Dental enamel hypoplasia, nail dystrophy
- Alopecia areata or totalis
- Vitiligo
- Autoimmune hepatitis
- Type 1 diabetes
- Autoimmune thyroiditis
- Pernicious anemia
- Autoimmune ovarian/testicular failure

**Why does AIRE deficiency cause candidiasis?**
- Patients develop neutralizing autoantibodies against IL-17A, IL-17F, and IL-22
- These cytokines are essential for mucosal defense against Candida
- The autoantibodies functionally impair Th17-mediated immunity
- This case demonstrates positive anti-IL-17 and anti-IL-22 antibodies

**Epidemiology:**
- More common in Finnish, Iranian Jewish, and Sardinian populations
- Autosomal recessive inheritance (consanguinity is a risk factor)

### Treatment
1. **Hypoparathyroidism:** Calcium and calcitriol (active vitamin D) supplementation
2. **Chronic mucocutaneous candidiasis:** Long-term antifungal therapy (fluconazole, itraconazole)
3. **Surveillance for additional autoimmune manifestations:**
   - Annual screening for adrenal insufficiency (cortisol, ACTH)
   - Monitor for diabetes, thyroid disease, hepatitis
4. **Hormone replacement:** As needed for each endocrinopathy
5. **Genetic counseling:** For autosomal recessive inheritance
6. **No disease-modifying therapy available:** Treatment is supportive and directed at individual manifestations