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Coeliac disease

Introduction and epidemiology

Coeliac disease, also called coeliac sprue or gluten-sensitive enteropathy, is a chronic immune-mediated systemic disorder triggered by consumption of gluten.

It’s a relatively common condition, affecting 1 per 100 in Western Europe, but it’s also common in the Middle East. The prevalence has increased significantly in the recent 50 years. It’s likely underdiagnosed due to its heterogenous clinical presentation.

Etiology

Coeliac disease is highly related to genetic susceptibility, namely the HLA DQ2 (95%) and DQ8 (5%) variants. The disease can develop in the absence of these factors, but it’s extremely rare. Presence of other autoimmune disorders is also a risk factor.

Pathomechanism

When gluten is digested, it will be degraded in the intestines. The gliadin molecule is unable to be digested by our bodies and will only become deaminated. The deaminated gliadin then interacts with the HLA-molecules on antigen-presenting cells. In individuals with the HLA-DQ2/HLA-DQ8 allele, gliadin will be recognized as a pathogen by the CD4+ and initiate an immune response. Cytokines by CD4+ cells will cause damage of the mucosa, and CD8+ cells not specific for gliadin accumulate as well and cause damage. B-cells response follows and results in formation of anti-deaminated gliadin antibodies.

Clinical features

Typical symptoms include diarrhoea, abdominal pain, bloating, and weight loss. In severe cases, nutrient deficiencies and extraintestinal manifestations (dermatitis herpetiformis, arthritis, +++) may develop. However, many have different presentations.

Diagnosis and evaluation

For diagnosis of coeliac disease, the patient must be on a gluten-containing diet for some time, to allow the pathological signs to appear. Presence of anti-tTG, anti-EMA, and anti-DGP antibodies is characteristic but unfortunately not diagnostic alone for coeliac disease, except in children. In adults, upper endoscopy with biopsy is required for the diagnosis.

Histological severity is classified according to the Marsh classification from Marsh 1 to 3c.

Treatment

The treatment is a strict gluten-free diet for life.

Malabsorption syndromes

Introduction

Malabsorption syndrome refers to a number of disorders in which the small intestine can’t properly absorb one or more nutrients. This may be due to impaired absorption or impaired digestion.

Fat malabsorption is the most common specific nutrient malabsorption.

Etiology

• Global/complex nutrient malabsorption
  • Exocrine pancreatic insufficiency (chronic pancreatitis, pancreatic duct obstruction, CF)
  • Intestinal resection
  • Inflammatory bowel disease
  • Coeliac disease
  • Gastroenteritis
• Fat malabsorption
  • Cholestasis
  • Bile acid malabsorption
  • Orlistat
• Carbohydrate malabsorption
  • Lactose intolerance

Clinical features

Intestinal symptoms include diarrhoea, steatorrhoea (in fat malabsorption), bloating, and abdominal pain. In some cases, extraintestinal symptoms like anaemia, weight loss, nutrient deficiency, and oedema may develop. Some symptoms are specific to certain types of malabsorption:

• Fat malabsorption – pale stool, steatorrhoea
• Protein malabsorption – oedema, muscle atrophy
• Carbohydrate malabsorption – water diarrhoea, flatulence

Diagnosis and evaluation

Many tests can be useful in the evaluation of malabsorption:

• Serum ferritin – marker of iron absorption
• Serum protein and albumin– marker of protein absorption
• Microscopic examination of fat content in stool – marker of fat absorption
• Hydrogen breath test – test for carbohydrate absorption
  • After consumption of a carbohydrate (usually lactose), serial measurements of hydrogen in the breath are made. Abnormally high levels of hydrogen in the breath in a sign of malabsorption of that carbohydrate
• D-xylose absorption test – test for small bowel mucosal defects
  • D-xylose is passively absorbed through healthy bowel mucosa. If, following administration of this monosaccharide, serum and urine levels are low, it can be concluded that the bowel mucosa has defects
• Stool culture – for parasites which impair absorption
• Bile salt breath test/SeHCAT test – test for bile salt absorption, no longer used
• Shilling test – test for B12 absorption, no longer used