DEFINITION & EPIDEMIOLOGY
- Definition: T-cell-mediated chronic inflammatory enteropathy with autoimmune component. Triggered by ingestion of gluten in genetically susceptible individuals.
- Prevalence: Approximately 1% in US and Europe. Higher seroprevalence in symptomatic pediatric populations.
- Demographics: Female predominance (2-3:1). Can present at any age following gluten introduction.
PATHOPHYSIOLOGY
- Environmental Trigger: Gluten (found in wheat, rye, barley). Composed of gliadins and glutenins.
- Peptide Resistance: High glutamine and proline content prevents complete enzymatic digestion in gastrointestinal tract.
- Permeability: Gliadin enhances paracellular permeability (zonulin-mediated pathway), crossing intestinal epithelium into lamina propria.
- Deamidation: Tissue transglutaminase 2 (tTG) deamidates gliadin peptides.
- Antigen Presentation: Deamidated peptides exhibit high affinity for HLA-DQ2 or HLA-DQ8 molecules on antigen-presenting dendritic cells.
- Immune Activation: Presentation to CD4+ T-cells drives TH1-predominant cytokine response (Interferon-gamma, IL-15, IL-21).
- Mucosal Damage: Cascade results in intraepithelial lymphocytosis, crypt hyperplasia, and villous atrophy.
- Autoantibody Production: B-cells produce celiac-specific antibodies: anti-tTG, anti-endomysial (EMA), and anti-deamidated gliadin peptide (DGP).
GENETICS & ASSOCIATIONS
- Genetic Susceptibility: >95% possess HLA-DQ2 allele (HLA-DQA105/DQB102); remainder possess HLA-DQ8.
- Heritability: 75% concordance in monozygotic twins; 10% prevalence among first-degree relatives.
High-Risk Associated Conditions
Screening recommended for asymptomatic children with:
- Type 1 Diabetes Mellitus (10% prevalence)
- Autoimmune thyroid disease (Hashimoto, Graves)
- Selective IgA deficiency
- Down syndrome, Turner syndrome, Williams-Beuren syndrome
- Autoimmune liver disease
- Juvenile idiopathic arthritis
CLINICAL PRESENTATION (OSLO DEFINITIONS)
Spectrum ranges from severe malabsorption to asymptomatic.
| Classification | Clinical Features & Nuances |
|---|---|
| Classic (Malabsorptive) | Early onset (9–24 months). Chronic diarrhea, weight loss, failure to thrive, abdominal distension, muscle wasting, anorexia, irritability, vomiting. |
| Nonclassic (Extra-intestinal) | Later childhood/adolescence presentation. Short stature, delayed puberty, refractory iron deficiency anemia, dental enamel hypoplasia, recurrent aphthous stomatitis, osteoporosis, dermatitis herpetiformis, hypertransaminasemia, arthritis, alopecia areata. |
| Subclinical / Silent | No apparent signs/symptoms triggering evaluation; diagnosed via screening of high-risk groups (positive serology & histology). |
| Potential | Positive celiac serology; normal small intestinal mucosa. May or may not develop enteropathy later. |
| Refractory | Persistent/recurrent malabsorptive symptoms and villous atrophy despite strict gluten-free diet >12 months. Rare in children. |
Celiac Crisis
- Rare, acute, life-threatening presentation.
- Explosive diarrhea, profound hypoproteinemia, metabolic acidosis, severe dehydration, lethargy.
DIAGNOSTIC EVALUATION
Testing mandates concurrent gluten-containing diet.
1. Serological Testing
- First-line Screen: Tissue transglutaminase (tTG) IgA + Total Serum IgA.
- Note: Total IgA excludes Selective IgA Deficiency (2% of celiac patients).
- IgA Deficient Patients: Evaluate using IgG-based assays (IgG tTG, IgG DGP, or IgG EMA).
- Anti-Endomysial Antibody (EMA) IgA: High specificity; observer-dependent immunofluorescence assay. Used as confirmatory test.
- Deamidated Gliadin Peptide (DGP): Useful adjunct, especially IgG DGP in IgA-deficient patients or children <2 years old.
2. ESPGHAN 2020 No-Biopsy Algorithm
Diagnosis confirmed without duodenal biopsy if ALL criteria met:
- Symptomatic or asymptomatic child.
- Initial tTG-IgA titer 10x Upper Limit of Normal (ULN).
- Positive EMA-IgA drawn on a second, separate blood sample.
- Note: HLA typing no longer mandatory for no-biopsy pathway.
3. Endoscopy & Histology
Gold standard when no-biopsy criteria unmet (tTG-IgA <10x ULN).
- Endoscopic Markers: Scalloping of duodenal folds, mosaic pattern, nodularity, loss of circular folds, visible submucosal vessels. (50% sensitivity; normal appearance does not exclude disease).
- Biopsy Protocol: Minimum 4 biopsies from distal duodenum + 1-2 biopsies from duodenal bulb (disease may be patchy or isolated to bulb).
Modified Marsh-Oberhuber Histological Classification
| Stage | Description | Histological Findings |
|---|---|---|
| Type 0 | Pre-infiltrative | Normal mucosa. |
| Type 1 | Infiltrative | Normal villous architecture; Increased intraepithelial lymphocytes (IELs >30/100 enterocytes). |
| Type 2 | Hyperplastic | Increased IELs + Crypt hyperplasia. |
| Type 3a | Destructive (Mild) | Increased IELs + Crypt hyperplasia + Mild villous atrophy. |
| Type 3b | Destructive (Moderate) | Increased IELs + Crypt hyperplasia + Marked villous atrophy. |
| Type 3c | Destructive (Severe) | Increased IELs + Crypt hyperplasia + Total flattening of villi. |
4. Genetic Testing (HLA DQ2/DQ8)
- High negative predictive value.
- Absence of DQ2/DQ8 makes celiac disease highly unlikely.
- Useful for excluding disease in diagnostically uncertain cases or screening at-risk groups (Down syndrome, T1DM) to eliminate need for future serologic screening.
DIFFERENTIAL DIAGNOSIS
| Category | Conditions |
|---|---|
| Mucosal Damage / Enteropathy | Autoimmune enteropathy, Crohn disease, Eosinophilic gastroenteritis, Tropical sprue, Cow’s milk protein allergy. |
| Digestive/Enzyme Deficiency | Lactose malabsorption, Sucrase-isomaltase deficiency, Cystic fibrosis (pancreatic insufficiency). |
| Non-Celiac Gluten Sensitivity | GI/non-GI symptoms upon gluten ingestion, lacking enteropathy and lacking specific autoantibodies. |
MANAGEMENT
Strict, lifelong elimination of gluten remains the sole medical therapy.
1. Dietary Intervention
- Gluten-Free Diet (GFD): Absolute avoidance of wheat, rye, barley, and derivatives (triticale, kamut, spelt, malt).
- Threshold: Daily gluten intake must remain <10-50 mg to prevent histological damage.
- Oats: Pure, uncontaminated oats are safe and tolerated by majority; add sequentially after disease remission.
2. Nutritional Rehabilitation
- Screen for and treat micronutrient deficiencies: Iron, Folate, Vitamin D, Calcium, Vitamin B12.
- Lactose Avoidance: Transient secondary lactase deficiency common at diagnosis due to villous brush-border damage. Implement low-lactose diet temporarily.
- Assess bone health (DEXA scan) if classical severe malabsorptive symptoms present.
3. NIH “CELIAC” Mnemonic for Management
- C: Consultation with skilled dietitian.
- E: Education about disease.
- L: Lifelong adherence to GFD.
- I: Identification/treatment of nutritional deficiencies.
- A: Access to advocacy group.
- C: Continuous long-term follow-up.
4. Long-Term Monitoring
- Assess dietary compliance, growth (BMI, height velocity), and symptom resolution.
- Serial tTG-IgA testing at 6 months, then annually. Titers should decline/normalize within 12 months on strict GFD.
- Follow-up intestinal biopsy not routinely indicated if clinical and serological response achieved.
COMPLICATIONS & PROGNOSIS
- Nonresponsive Celiac Disease: Persistent symptoms/serology. Most common cause: intentional or inadvertent ongoing gluten ingestion.
- Growth Failure: Untreated disease results in permanent short stature. Excellent catch-up growth typically observed if treated before puberty.
- Malignancy Risk: Enteropathy-associated T-cell lymphoma (EATL) or small bowel adenocarcinoma. Increased risk in adulthood if untreated; minimized to baseline population risk with strict GFD compliance.
- Autoimmune Propagation: Continued gluten exposure hypothesized to increase risk of concurrent autoimmune diseases (T1DM, thyroiditis).