Celiac disease

Etiology

Genetic predisposition with association to HLA antigens
- HLA-DQ2 in 90–95% of patients
- HLA-DQ8 in 5–10% of patients
Consuming gliadin from grains such as wheat, rye, and barley leads to an autoimmune reaction within the small intestinal wall.

Symptoms manifest when a genetically predisposed individual develops an immunological response to gliadin, an alcohol-soluble fraction of gluten.
Consumption of food containing gluten → tissue transglutaminase is released → modifies gliadin from gluten proteins → pathogenic T cells react to and are activated by modified gliadin → mediate chronic intestinal inflammation → epithelial damage resulting in villous atrophy, crypt hyperplasia, and loss of brush border → impaired resorption of nutrients in the small intestine (especially in the distal duodenum and proximal jejunum) → malabsorption symptoms

Malabsorption symptoms: fatigue, weight loss, vitamin deficiency, iron deficiency anemia, osteoporosis, hypocalcemia
In children: failure to thrive, growth failure, delayed puberty, secondary hyperparathyroidism
Dermatologic associations: dermatitis herpetiformis
- Transglutaminases play a role in forming extensively cross-linked proteins (e.g., elastin, coagulation by factor XIII).
Neuropsychiatric symptoms: peripheral neuropathies (numbness, burning and tingling of the hands and feet) , headache, ataxia, depression, irritability
Commonly associated with autoimmune diseases

IgA tissue transglutaminase antibody (tTG IgA): initial test
Total IgA
- Indicated for all patients because of the high prevalence of IgA deficiency in patients with celiac disease (approx. 2–3%)
  - Both celiac disease and selective IgA deficiency have strong associations with specific HLA genes, particularly HLA-DQ2 and HLA-DQ8.
- If patients have low IgA, perform further IgG-based testing.
Deamidated gliadin peptide
- IgG-based testing: indicated in IgA deficiency or discordant biopsy and serology
  - IgG-tissue transglutaminase (tTG IgG)
  - IgG deamidated gliadin peptide (DGP IgG)
- IgA-based testing: IgA deamidated gliadin peptide (DGP IgA)
Anti-endomysial antibody (EMA): Potential second-line confirmatory test (high-specificity)
Celiac disease is not associated with elevated systemic inflammatory markers (eg, C-reactive protein, erythrocyte sedimentation rate), since it's limited.

EGD with small intestine biopsy (confirmatory test)
- Intraepithelial lymphocytic infiltration
- Crypt hyperplasia
- Villous atrophy

Definition: A disease characterized by chronic diarrhea with subsequent malabsorption in association with a stay in the tropics or subtropics.
Epidemiology: occurs in residents of the tropics and subtropics or in travelers returning from these areas (after trips lasting several weeks)
Etiology: exact cause not known; most likely due to bacterial infection that leads to structural damage of the intestinal mucosa
Clinical features: similar to Celiac disease
Diagnostics
- Endoscopy of the small bowel and biopsy: villous atrophy, elongated crypts, presence of inflammatory cells (plasma cells, lymphocytes, eosinophils)
Treatment: tetracycline in combination with folic acid for 3–6 months

Strict, lifelong gluten-free diet
- Abstain from products containing wheat, rye, barley, or spelt.
- Symptoms usually improve quickly