Disorders triggered by gluten - types and diagnosis

Celiac disease is a chronic, systemic autoimmune disorder with genetic etiology, arising exclusively in genetically predisposed individuals expressing human leukocyte antigens HLA-DQ2 or HLA-DQ8. It is driven by permanent dietary intolerance to gluten—storage proteins found in wheat (gliadin), rye (secalin), and barley (hordein). Gluten ingestion triggers an aberrant cell-mediated immune cascade in the small intestine, precipitating mucosal inflammation, villous atrophy, crypt hyperplasia, and intraepithelial lymphocytosis, which culminates in multi-nutrient malabsorption.

Contemporary clinical gastroenterology categorizes celiac disease into three primary clinical presentations:

• Classic (full-blown) celiac disease: Dominated by gastrointestinal symptoms, including chronic malabsorptive diarrhea, steatorrhea, abdominal distension, progressive weight loss, and secondary deficiencies such as microcytic iron-deficiency anemia and failure to thrive in pediatric cohorts.
• Non-classic (oligosymptomatic) celiac disease: Represents the prevailing presentation, diagnosed five times more frequently than classic forms. Gastrointestinal complaints are mild or absent; manifestations are predominantly extraintestinal, including recurrent aphthous stomatitis, refractory osteopenia, hypertransaminasemia, gluten ataxia, peripheral neuropathy, and unexplained reproductive disorders.
• Potential (latent) celiac disease: Characterized by circulating serum celiac-specific autoantibodies alongside structurally intact intestinal mucosa (Marsh 0–1 histology), carrying potential risk of future mucosal progression.

Accurate clinical confirmation of celiac disease requires an evidence-based algorithm integrating serological, histological, and genetic parameters:

• Serological testing: Quantitative assay of serum IgA antibodies against tissue transglutaminase (anti-tTG IgA) coupled with total serum IgA measurement to rule out selective IgA deficiency. When IgA deficiency is confirmed, IgG-based markers (anti-tTG IgG or deamidated gliadin peptide anti-DGP IgG) are mandated. Endomysial antibodies (EMA-IgA) provide high confirmatory specificity.
• Histopathological evaluation: Upper endoscopy with multiple duodenal biopsies (at least 1–2 from the bulb and 4 from the distal duodenum), graded via the Marsh-Oberhuber classification system ranging from intraepithelial lymphocytosis to total villous atrophy. Per ESPGHAN pediatric criteria, duodenal biopsy may be safely omitted if anti-tTG titers exceed 10 times the upper limit of normal alongside positive EMA in an independent blood sample.
• Genetic typing: Genotyping for HLA-DQ2 and HLA-DQ8 carries exceptional negative predictive value (>99%); absence of both heterodimers virtually excludes celiac disease.

Critical Clinical Caveat: Diagnostic screening must strictly be performed while the patient consumes a gluten-containing diet. Premature dietary elimination causes serological antibody clearance and mucosal healing, inducing false-negative conclusions.

Wheat allergy is an immunological hypersensitivity reaction, predominantly IgE-mediated (though non-IgE mechanisms exist), directed against diverse wheat protein fractions, including albumins, globulins, gliadins, and glutenins. Unlike celiac disease, wheat allergy does not trigger autoimmune destruction or intestinal mucosal villous atrophy.

Symptom onset is rapid, manifesting within minutes to several hours post-ingestion or inhalation, presenting as urticaria, angioedema, contact dermatitis, bronchospasm, abdominal cramping, emesis, and potentially life-threatening anaphylaxis. In pediatric populations, wheat allergy demonstrates high rates of natural resolution by age 6. The therapeutic regimen requires strict exclusion of wheat-derived products only, whereas non-cross-reactive grains (rye, barley, certified gluten-free oats) remain permissible.

Non-celiac gluten/wheat sensitivity (NCGS) is clinically diagnosed in individuals who experience gastrointestinal and extraintestinal distress upon ingesting gluten-containing cereals, provided that celiac disease (negative serology and intact villous architecture) and wheat allergy (negative wheat-specific IgE) have been definitively excluded.

Pathophysiologically, NCGS involves innate immune activation. Causative dietary components encompass not only gluten prolamin peptides, but also wheat amylase-trypsin inhibitors (ATIs) and poorly absorbed short-chain carbohydrates (FODMAPs). Clinical features include chronic bloating, abdominal pain, diarrhea or constipation, accompanied by systemic symptoms such as cognitive fogginess ('brain fog'), chronic fatigue, headaches, and arthralgia. The gold standard for objective diagnosis remains a double-blind placebo-controlled crossover food challenge following a standardized trial of gluten exclusion.