In Japan, celiac Disease is managed by gastroenterologists. Celiac disease is an immune-mediated enteropathy in which dietary gluten triggers villous atrophy of the small intestine in genetically predisposed people who carry HLA-DQ2 or HLA-DQ8. Global seroprevalence sits near 1.4% and biopsy-confirmed prevalence near 0.7% (Singh et al, Clin Gastroenterol Hepatol 2018), yet roughly 70% of cases remain undiagnosed because presentations are often non-classical — iron deficiency, fatigue, osteopenia, infertility, or transaminitis rather than the textbook diarrhea and weight loss.
Celiac disease (ICD-10: K90.0) is a chronic immune-mediated enteropathy of the small intestine triggered by ingestion of gluten — the storage protein found in wheat, barley, and rye — in genetically susceptible individuals carrying the HLA-DQ2 or HLA-DQ8 class II haplotypes (present in over 99% of patients). Deamidated gluten peptides are presented to CD4+ T cells, driving an inflammatory cascade that destroys absorptive villi, deepens crypts, and infiltrates the epithelium with lymphocytes. The histologic spectrum is graded by the Marsh-Oberhuber classification from Marsh 0 (normal) through Marsh III (partial, subtotal, or total villous atrophy), with Marsh II or higher required for diagnosis. The resulting malabsorption affects iron, folate, vitamin B12, calcium, vitamin D, and fat-soluble vitamins.
The key symptoms of Celiac Disease are: Chronic or intermittent diarrhea, often pale, bulky, and foul-smelling due to fat malabsorption — present in around 40-50% of new adult diagnoses, less common than a generation ago., Abdominal pain, bloating, and excessive flatulence after meals containing wheat, barley, or rye., Unintentional weight loss in adults, or faltering growth and short stature in children., Iron deficiency anemia unresponsive to oral iron — present in up to 40% of newly diagnosed adults and often the only sign., Persistent fatigue and reduced exercise tolerance, frequently attributed to anemia or B-vitamin deficiency., Dermatitis herpetiformis — intensely itchy, symmetric vesicular rash on elbows, knees, buttocks, and scalp; pathognomonic skin form of celiac disease, present in about 10-15% of patients., Recurrent mouth ulcers (aphthous stomatitis) and enamel defects on permanent teeth — common in pediatric and young adult patients..
Diagnosis of celiac disease begins with serology while the patient is still eating a gluten-containing diet — at least 3 g of gluten daily (about two slices of wheat bread) for 6-8 weeks before testing. The first-line test is serum IgA tissue transglutaminase antibody (IgA tTG), which has a pooled sensitivity around 95% and specificity around 95% in symptomatic adults. Total serum IgA is measured at the same time to identify selective IgA deficiency (2-3% of celiac patients), in which case IgG-based testing — IgG deamidated gliadin peptide (DGP) or IgG tTG — is substituted. Endomysial antibody (EMA) is highly specific (close to 100%) and is used as a confirmatory tier when IgA tTG is positive but biopsy is delayed or uncertain. The reference standard in adults is upper endoscopy with duodenal biopsy, taking at least four samples from the distal duodenum plus two from the duodenal bulb (ACG 2023). Histology is graded by the Marsh-Oberhuber system, and a finding of Marsh II or higher in a seropositive patient confirms the diagnosis. ESPGHAN 2020 endorses a no-biopsy pathway in symptomatic children when IgA tTG exceeds 10x the upper limit of normal, confirmed by a positive EMA on a separate sample — this has been adopted into pediatric practice in much of Europe and increasingly in adults under selected criteria. HLA-DQ2/DQ8 genotyping has high negative predictive value: a negative result essentially rules out celiac disease and is useful in equivocal scenarios such as a patient already on a gluten-free diet or biopsy-positive but seronegative cases. Differential diagnosis includes non-celiac gluten sensitivity, wheat allergy, microscopic colitis, tropical sprue, common variable immunodeficiency enteropathy, autoimmune enteropathy, and small intestinal bacterial overgrowth.
With strict, lifelong adherence to a gluten-free diet, the long-term prognosis for celiac disease is excellent and life expectancy approaches that of the general population. Symptoms improve within weeks, serology normalizes by 6-24 months, and mucosal healing reaches Marsh 0-I in 65-85% of adults and over 95% of children within 1-2 years. Bone mineral density rises measurably in the first year and continues to recover for several years. Untreated or partially treated disease carries a meaningfully increased risk of osteoporosis, infertility, anemia, autoimmune comorbidity, refractory celiac disease (1-2% of adults), small bowel adenocarcinoma, and enteropathy-associated T-cell lymphoma — the last of these accounts for most of the modestly elevated mortality reported in older cohort studies. The strongest predictor of good outcome is dietary adherence, which is best supported by ongoing dietitian review, family education, and engagement with celiac patient organizations.
Refer to a gastroenterologist for confirmatory duodenal biopsy in any adult with positive celiac serology, for evaluation of persistent symptoms or positive serology after 12 months on a strict gluten-free diet, for suspected refractory celiac disease, and for surveillance of complications including small bowel lymphoma or adenocarcinoma. A registered dietitian with celiac expertise is essential at diagnosis and at follow-up: structured dietitian-led education is associated with measurably better adherence and faster mucosal healing.
Find specialists →Symptom improvement begins within 1-4 weeks of a strict gluten-free diet for most adults. Energy, mood, and bowel habits typically stabilize by 2-3 months. Serology (IgA tTG) trends downward by 6 months and normalizes in 60-80% of patients by 12 months. Histologic recovery to Marsh 0-I takes 1-2 years in 65-85% of adults; children heal faster, usually within 6-12 months. Bone density improvements are measurable on DEXA at 12 months and continue for 2-3 years.
Regular weight-bearing and resistance exercise is strongly recommended to rebuild bone mass once the gluten-free diet has begun, given the high prevalence of osteopenia at diagnosis. Aim for 150 minutes of moderate aerobic activity per week plus 2-3 resistance sessions. Endurance athletes should plan gluten-free fueling carefully: many sports drinks, gels, and recovery products contain gluten-derived ingredients. Performance typically returns to baseline once nutritional deficiencies and anemia are corrected, usually within 6-12 months.
Choose a gastroenterologist with experience in autoimmune enteropathies and access to a dietitian trained in gluten-free diet counseling. Confirm the practice routinely takes 4-6 duodenal biopsies (distal duodenum plus bulb) — single-site biopsies miss patchy villous atrophy in up to 10% of cases. Ask whether the unit performs HLA-DQ2/DQ8 testing in-house and runs a structured non-responsive celiac protocol. Continuity of care matters — celiac disease is a lifetime condition and a long-term relationship with a clinician familiar with your history improves outcomes.
Medically reviewed by AIHealz Medical Editorial Board · May 12, 2026
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