Celiac Disease

Celiac disease is an immune mediated enteropathy triggered by dietary gluten (wheat, barley, rye) in genetically susceptible people carrying HLA DQ2 or DQ8.

• Prevalence is about 1% worldwide, and most cases remain undiagnosed.
• Tissue transglutaminase deamidates gliadin peptides, which drives a CD4 T cell response, intraepithelial lymphocytosis, crypt hyperplasia and villous atrophy.
• First degree relatives have a 5 to 15% risk.
• Associations: type 1 diabetes, autoimmune thyroid disease, Down syndrome, Turner syndrome, IgA deficiency, autoimmune hepatitis, Addison disease. Complications include osteoporosis, iron deficiency, infertility, refractory celiac disease, enteropathy associated T cell lymphoma and small bowel adenocarcinoma.

The classic form causes chronic diarrhoea, steatorrhoea, weight loss and bloating, but most adults present with non gastrointestinal features.

• Iron deficiency anaemia unresponsive to oral iron, folate or B12 deficiency, osteopenia, elevated transaminases, aphthous ulcers, dental enamel defects.
• Dermatitis herpetiformis: itchy grouped vesicles on elbows, knees and buttocks.
• Neurological: ataxia, peripheral neuropathy. Reproductive: recurrent miscarriage, delayed puberty.
• Children: failure to thrive, short stature, irritability. Red flags are weight loss, abdominal pain and fever despite a gluten free diet, which suggest refractory disease or lymphoma.

Testing must be done on a gluten containing diet (at least 3 slices of bread daily for 6 weeks).

• First test is IgA anti tissue transglutaminase with total IgA. If IgA deficient, use IgG tTG or IgG deamidated gliadin peptide.
• Endomysial antibodies confirm positive results.
• Duodenal biopsy (at least 4 from the second part and 1 or 2 from the bulb) shows Marsh grade 3 changes (villous atrophy, crypt hyperplasia, intraepithelial lymphocytes over 25 per 100 enterocytes).
• Children with tTG over 10 times the upper limit of normal, positive EMA and symptoms may be diagnosed without biopsy.
• HLA DQ2/DQ8 testing has a high negative predictive value and is used when serology and histology are discordant or the patient is already on a gluten free diet.
• Baseline: full blood count, ferritin, B12, folate, vitamin D, calcium, liver tests, TSH, DEXA.

• Lifelong strict gluten free diet with dietitian support. Recovery of symptoms in weeks, of serology in 6 to 12 months, and of histology in 1 to 2 years.
• Replace deficiencies: ferrous sulfate 200 mg daily (or IV iron), folic acid 5 mg daily, hydroxocobalamin 1 mg IM, vitamin D 800 to 2000 IU daily, calcium 1000 mg daily.
• Dermatitis herpetiformis: dapsone 25 to 100 mg daily after checking G6PD.
• Osteoporosis: bisphosphonate (alendronate 70 mg weekly) once vitamin D is replete.
• Vaccination: pneumococcal vaccine (functional hyposplenism), hepatitis B.
• Follow up annually with tTG, full blood count, ferritin, B12, TSH and symptom review. Screen first degree relatives.
• Persistent symptoms: review for inadvertent gluten ingestion, then exclude lactose intolerance, small bowel bacterial overgrowth, microscopic colitis, pancreatic insufficiency.
• Refractory celiac disease (symptoms with villous atrophy despite 12 months of strict diet): type 1 (normal T cells) is treated with budesonide 9 mg daily or prednisolone 40 mg tapered, azathioprine 2 mg/kg. Type 2 (aberrant clonal T cells) needs cladribine or autologous stem cell transplant and carries high lymphoma risk.
• Nutritional support with parenteral nutrition for severe malabsorption.