Malabsorption Syndrome Flashcards
How common is Coeliac disease?
Affects ~ 1% of UK population
What is Coeliac disease?
- intolerance to gluten
- in particular, gliadin, the alcohol-free fraction of gluten, is the disease-producing component
- gluten is found in wheat, barley and rye
What is the brief pathogenesis of coeliac disease?
- not fully understood
- thought that gliadin triggers inappropriate activation
- of intestinal T cells
- in genetically susceptible individuals (ppl w/ HLA-DQ2 and HLA-DQ8 haplotypes)
- resulting in damage to epithelial cells
Now explain in more detail what happens in patients with coeliac when gluten is digested in comparison to a healthy individual?
- gluten digested by luminal and brush-border enzymes in small intestine
- into aino acids + peptides, incl 33AA gliadin peptide
- gliadin is deamidated in mucosa by tissue transglutaminases (tTG)
- in those w/ HLA-DQ2 and HLA-DQ8 haplotypes, deamidated gliadin closely fits the MHC II grooves
- gliadin presented to T helper cells by antigen presenting cells
- initiates a Th2-predominant immune response
- generates cytotoxic T cells against gliadin
- cytotoxic T cells migrate into intestinal epithelium, visible on biopsy as intraepithelial lymphocytes
- the T cells damage + destroy epithelial cells resulting in progressive villous atrophy
- as a result, crypts become hyperplastic to compensate for cell loss
- loss of normal small bowel fxn -> malabsorption
- also a humoral immune response w/ generation of antigliadin, antiendoymysial and antiTTG antibodies - useful antibodies diagnostically
What is the clinical presentation of coeliac disease?
- at any age, most commonly in childhood or middle age
- symptoms of malabsorption (diarrhoea, steatorrhoea, weight loss, lethargy, bloating, abdo pain)
- non-specific symptoms: eg. anaemia (usually iron def), irritable bowel syndrome-like symptoms, altered bowel habit, abdo pain
- in children, coeliac disease is an important cause of failure to thrive and delayed puberty
- an intensely itchy and blistering rash over elbows + buttocks - dermatitis herpetiformis
- some pts are asymptomatic and diagnosis is discovered incidentally
How is coeliac disease diagnosed?
- history and examination
- gluten-containing diet better to be consumed during diagnostic process
- serology tests: total IgA and IgA tissue transglutaminase antibodies are currently the preferred first line test (owing to its high sensitivity and negative predictive value)
- IgA anti-endomysial (EMA) antibodies can be used if IgA tTG is weakly positive
- gold standard ix: endoscopy and duodenal biopsy
What does tissue biopsy for positive coeliac show?
- villous atrophy
- crypt hyperplasia
- prominent intraepithelial lymphocytes
Generally agreed that duodenal biopsy should be performed on all adult patients to confirm the diagnosis
What is the treatment for coeliac?
- Life-long gluten-free diet
- Those with coeliac disease (+ fam members, carers) should be given sources of info on the disease, including a national and local specialist coeliac groups and dietiticans with a specialist knowledge of coeliac disease
What are complications of coeliac disease?
- Malabsorption (-> anaemia + deficiencies)
- Osteopenia/osteoporosis
- Dermatitis herpetiformis
- Lymphoma
Why do patients with coeliac develop osteopenia/osteoporosis? How can this be investigated and treated?
- most pts w/ coeliac disease are osteopenic (reduced bone density)
- bc they fail to reach their peak bone mass during young adult life
- due to malabsorption of calcium
- reduction in bone density is usually mild, most pts are only osteopenic
- however, some are actually osteoporotic w/ associated risk of fracture
- at dx, pts given lifestyle advice + basline DEXA scan to assess bone mineral density
- pts should maintian adequate calcium and vit D intake
- a gluten-free diet should prevent further bone loss and may improve bone density
Why do coeliac patients develop dermatitis herpetiformis?
- intensely itchy chronic blistering skin condition
- typically occurs symmetrically on extensor surfaces (buttocks, back of neck, knees, elbows etc)
- it’s not related to herpes virus
- rather, associated w/ coeliac disease although exact mechanism not fully understood
- may be due to autoantibodies to epidermal transglutaminase