# Clinical Cases: Nutrition and Malabsorption

## Case 1: Celiac Disease with Malabsorption

### Patient Presentation
**Demographics:** 32-year-old female

**Chief Complaint:** Chronic diarrhea, bloating, and fatigue for 18 months

**History of Present Illness:** The patient has experienced progressive symptoms over 18 months including 4-6 loose, foul-smelling, greasy stools daily that are pale and float in the toilet bowl. She has significant bloating and abdominal discomfort, particularly after eating bread and pasta. She has lost 18 pounds unintentionally despite maintaining her usual diet. She reports profound fatigue, difficulty concentrating, and an intensely itchy rash on her elbows and knees that comes and goes.

**Past Medical History:** Iron deficiency anemia (treated with oral iron with minimal response), hypothyroidism (on levothyroxine), first-degree relative (mother) with celiac disease

**Social History:** Non-smoker, rare alcohol use

### Physical Examination
- **Vital Signs:** Normal
- **General:** Thin female appearing fatigued
- **Skin:** Grouped vesicular lesions with excoriations on extensor surfaces of elbows and knees bilaterally (dermatitis herpetiformis)
- **Mouth:** Angular cheilosis, glossitis with smooth tongue
- **Abdomen:** Soft, mild diffuse tenderness, hyperactive bowel sounds, no organomegaly
- **Extremities:** Mild pitting ankle edema

### Workup and Results
- **CBC:** Hemoglobin 9.8 g/dL, MCV 76 fL (microcytic), Platelets 420,000
- **Iron Studies:** Ferritin 8 ng/mL (low), Serum iron 25 mcg/dL (low), TIBC 450 mcg/dL (elevated), Transferrin saturation 6% (low)
- **Vitamin Levels:** Vitamin D 8 ng/mL (severely deficient), Folate low-normal, B12 normal
- **CMP:** Albumin 3.0 g/dL (low), Calcium 8.0 mg/dL (low)
- **Celiac Serology:**
  - Total IgA: Normal (rules out IgA deficiency that would cause false-negative)
  - **Tissue Transglutaminase IgA (tTG-IgA): 145 U/mL** (normal < 4; markedly elevated)
  - Anti-endomysial antibody (EMA): Positive
- **DEXA Scan:** T-score -2.8 at lumbar spine (osteoporosis)
- **Upper Endoscopy with Duodenal Biopsies:** Scalloped, fissured duodenal folds with loss of normal villi; histology shows villous atrophy, crypt hyperplasia, and increased intraepithelial lymphocytes (> 40 per 100 enterocytes) - Marsh IIIb

![Celiac Disease Endoscopy](case_01_image.jpg)
*Endoscopic image of the duodenum in celiac disease showing characteristic findings: scalloped duodenal folds with fissures and loss of normal villous pattern (mosaic pattern). These endoscopic changes correlate with villous atrophy seen on histology.*

**Image Source:** Wikimedia Commons. Samir, CC BY-SA 3.0

### Diagnosis
**Celiac Disease (Gluten-Sensitive Enteropathy) with:**
- Malabsorption (steatorrhea, weight loss)
- Iron-refractory iron deficiency anemia
- Vitamin D deficiency with osteoporosis
- Dermatitis herpetiformis

### Clinical Correlation
Celiac disease is an autoimmune enteropathy triggered by gluten (from wheat, barley, rye) in genetically susceptible individuals (HLA-DQ2 or HLA-DQ8 positive). Key teaching points:

**Pathophysiology:**
- Gluten peptides (specifically gliadin) cross the intestinal epithelium
- Tissue transglutaminase (tTG) deamidates gliadin, creating neoantigens
- These are presented to T cells by HLA-DQ2/DQ8, triggering an immune response
- Results in mucosal inflammation, villous atrophy, and malabsorption

**Why This Patient Has Specific Deficiencies:**
- **Iron deficiency (refractory to oral iron)**: Iron is absorbed in the duodenum - the most affected region in celiac disease
- **Vitamin D deficiency**: Fat-soluble vitamin malabsorption due to impaired fat absorption
- **Osteoporosis at young age**: Calcium and vitamin D malabsorption
- **Steatorrhea**: Mucosal damage impairs fat absorption (fat malabsorption occurs early)

**Dermatitis Herpetiformis:**
- Cutaneous manifestation of celiac disease (present in ~15-25% of celiac patients)
- IgA deposits in dermal papillae cause intensely pruritic vesicular lesions
- Classic distribution: extensor surfaces (elbows, knees), buttocks, scalp
- Responds to gluten-free diet and dapsone

**Diagnostic Approach:**
1. Serologic testing while patient is consuming gluten (tTG-IgA is 95% sensitive and specific)
2. Check total IgA to exclude IgA deficiency (causes false negatives)
3. Confirm with duodenal biopsy showing Marsh classification changes
4. Clinical and histologic response to gluten-free diet confirms diagnosis

### Treatment
- **Strict lifelong gluten-free diet** - eliminate all wheat, barley, rye; oats are usually tolerated but must be certified gluten-free (cross-contamination risk)
- **Nutritional supplementation:**
  - Iron supplementation (may need IV iron initially given malabsorption)
  - Vitamin D3 50,000 IU weekly until replete, then maintenance
  - Calcium supplementation (1000-1200 mg daily)
  - Consider vitamin A, E, K if deficient
- **Dermatitis herpetiformis**: Dapsone for symptom control; rash resolves with strict gluten-free diet over months to years
- **Referral to registered dietitian** experienced in celiac disease
- **Screen first-degree relatives** (10% prevalence in first-degree relatives)
- **Monitor for complications**: Repeat tTG-IgA at 6-12 months to assess dietary adherence; repeat DEXA after 1-2 years; rare lymphoma risk requires vigilance for persistent symptoms despite adherence

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## Case 2: Refeeding Syndrome

### Patient Presentation
**Demographics:** 19-year-old female

**Chief Complaint:** Admitted for severe malnutrition; now with new weakness and confusion on hospital day 3

**History of Present Illness:** The patient was admitted 3 days ago for severe malnutrition in the context of anorexia nervosa. She reports progressively restrictive eating over 2 years with minimal caloric intake for the past 3 months (estimated 200-400 kcal/day). On admission, she weighed 38 kg (BMI 14.2) and was bradycardic and hypothermic. She was started on nasogastric tube feeding yesterday at 1800 kcal/day.

Today (hospital day 3), she developed profound weakness, difficulty breathing, confusion, and palpitations. The nursing staff noted new pedal edema and decreased urine output.

**Past Medical History:** Anorexia nervosa (diagnosed age 16), depression, amenorrhea for 14 months

**Social History:** College student, lives with parents

### Physical Examination
**On Admission (Day 1):**
- Vital Signs: BP 88/52, HR 42 bpm, Temp 35.6C
- BMI: 14.2 (severely underweight)
- Cachectic female with temporal wasting, loss of subcutaneous fat, visible ribs

**On Hospital Day 3 (when symptoms developed):**
- Vital Signs: BP 98/60, HR 118 bpm (new tachycardia), RR 28/min (tachypnea)
- General: Confused, weak, unable to lift arms against gravity
- Cardiovascular: Tachycardic, no murmurs, JVD present
- Respiratory: Bilateral crackles at lung bases
- Extremities: 2+ pitting edema bilaterally (new)
- Neurologic: Confused, disoriented; positive Chvostek sign

### Workup and Results
**On Admission:**
- Phosphorus: 2.8 mg/dL (low-normal)
- Potassium: 3.4 mEq/L (low-normal)
- Magnesium: 1.7 mg/dL (low-normal)
- Glucose: 58 mg/dL

**On Hospital Day 3:**
- **Phosphorus: 0.8 mg/dL** (critically low; normal 2.5-4.5)
- **Potassium: 2.1 mEq/L** (critically low)
- **Magnesium: 1.0 mg/dL** (low)
- Glucose: 165 mg/dL
- BNP: 890 pg/mL (elevated; fluid overload)
- **ECG:** Sinus tachycardia, prolonged QT interval, flattened T waves, U waves (hypokalemia pattern)
- **Chest X-ray:** Pulmonary edema, small bilateral pleural effusions

### Diagnosis
**Refeeding Syndrome with:**
- Severe hypophosphatemia
- Severe hypokalemia
- Hypomagnesemia
- Fluid overload and pulmonary edema
- Cardiac stress (tachycardia, QT prolongation)
- Muscle weakness

### Clinical Correlation
Refeeding syndrome is a potentially fatal metabolic complication occurring when malnourished patients receive nutritional repletion. This case demonstrates classic pathophysiology:

**Why This Happened:**

1. **During Starvation:**
   - Insulin secretion decreases; body shifts to fat/protein catabolism
   - Intracellular phosphorus, potassium, and magnesium stores become depleted
   - Serum levels may appear normal (shift from intracellular to extracellular)
   - Thiamine stores are depleted

2. **Upon Refeeding (especially carbohydrate-rich):**
   - Insulin surges in response to glucose/carbohydrate load
   - Insulin drives glucose into cells for glycolysis
   - **Critically: Insulin also drives K+, Mg2+, and PO4 into cells**
   - Precipitous drop in serum levels as already-depleted cells take up minerals
   - Increased metabolic demand for thiamine (cofactor in carbohydrate metabolism)

**Consequences of Severe Hypophosphatemia:**
- Phosphorus is essential for ATP synthesis, 2,3-DPG (oxygen delivery), cell membranes
- **Respiratory failure**: Diaphragm weakness (ATP depletion)
- **Cardiac failure**: Impaired contractility
- **Rhabdomyolysis**: Muscle breakdown
- **Hemolysis**: Membrane instability, decreased 2,3-DPG

**Why She Developed Fluid Overload:**
- Refeeding causes sodium and water retention (insulin effect)
- Malnourished heart cannot handle volume load
- Leads to pulmonary edema and peripheral edema

**Risk Factors (This Patient Had Multiple):**
- BMI < 16
- Minimal intake for > 10 days
- Weight loss > 15% in 3-6 months
- History of anorexia nervosa

### Treatment
**Immediate Management:**
- **STOP enteral feeds** temporarily
- **IV Phosphorus replacement**: Sodium or potassium phosphate 15-30 mmol IV over 4-6 hours with cardiac monitoring
- **IV Potassium replacement**: Target K+ > 3.0 mEq/L with continuous ECG monitoring (QT prolongation risk)
- **IV Magnesium replacement**: 2-4 g IV over 2-4 hours
- **Thiamine 200-300 mg IV** - should have been given BEFORE any feeding was initiated
- Fluid restriction and diuresis for pulmonary edema
- Telemetry monitoring

**Resumption of Feeding (after electrolytes stabilize):**
- Restart feeding at **very low rate**: 5-10 kcal/kg/day
- Advance slowly: Increase by 5 kcal/kg/day every 1-2 days
- Target: Reach full caloric goal over 7-10 days
- **Monitor electrolytes twice daily** for first week

**Prevention Protocol (What Should Have Happened):**
1. Identify high-risk patients (BMI < 16, minimal intake, significant weight loss)
2. Check baseline electrolytes and correct before feeding
3. **Give thiamine 200-300 mg BEFORE first feeding** and continue for 3+ days
4. Start feeds at 10-20 kcal/kg/day (NOT full caloric needs)
5. Advance slowly over 5-7 days
6. Monitor electrolytes daily (or twice daily in highest risk)
7. Supplement phosphorus, potassium, magnesium prophylactically