Malabsorption in a child: Lactose intolerance Flashcards
Define lactose intolerance.
Inability to metabolise the carbohydrate lactose due to lactase deficiency.
Lactose intolerance is often confused with delayed non-IgE mediated cow’s milk protein allergy. Lactose intolerance is not immune mediated and is due to an intolerance of cow’s milk carbohydrate (sugar), not cow’s milk protein.
What are the three categories of lactose intolerance?
Congenital: Autosomal recessive condition.
Primary: Natural non-persistence of lactase enzyme after early childhood. Persistence of lactase is due to polymorphisms in the gene encoding for lactase (common in N. Europe).
Secondary: Damage to the intestinal brush border following gastroenteritis.
Explain the aetiology of lactose intolerance.
Disaccharide enzymes (for lactose, sucrose and maltose) are located at the brush border of the small intestine. The enzyme lactase breaks down lactose to glucose and galactose which can be absorbed into the bloodstream. For effective metabolism of lactose, only 50% lactase activity is required. Deficiency of lactase prevents hydrolysis of ingested lactose which results in an osmotic load in the gut and secretory diarrhoea. Abdominal pain and bloating are caused by bacterial fermentation of lactose in the colon.
Summarise the epidemiology of congenital lactose intolerance.
Extremely rare (40 cases known in the world).
Summarise the epidemiology of primary lactose intolerance.
5% (UK) to 17% in N. Europe increasing to >50% in Africa, Asia and South America.
Rarely presents before 5 years of age.
What are the presenting signs and symptoms of lactose intolerance.
GI: Loose stools (frothy and explosive), bloating and cramping abdominal pain, flatus.
Congenital: Infantile diarrhoea, failure to thrive.
Primary: GI symptoms increase with age due to progressive loss of lactase. There is a wide variety in the amount of lactose that individuals can tolerate.
Secondary: Preceding infective episode of diarrhoea.
What are appropriate investigations for lactose intolerance?
Hydrogen breath test: Detects hydrogen in breath 3–6 hours following ingestion of lactose. 20% will have a false-negative result due to hydrogen non-excretion.
Stools for reducing substances: Stools are acidic and contain undigested sugar.
Jejunal biopsies: Rarely needed to differentiate from coeliac disease.
What is the management for congenital lactose intolerance?
Life-long absolute avoidance of all traces of lactose. Lactose-free infant formulas and commercial lactosefree milk are available. Soya, rice, oat and pea milks are lactose free (recommend calcium-supplemented products). Rice milk is not recommended in children <4.5 years of age.
What is the management for primary lactose intolerance?
Low lactose diet is usually tolerated. These individuals may tolerate low lactose foods such as hard cheeses (Cheddar) and fermented yoghurts.
What is the management for secondary lactose intolerance?
Complete lactose avoidance is advised for 4–6 weeks to allow mucosal regeneration followed by gradual reintroduction of foods containing lactose.
What are complications associated with lactose intolerance?
Malabsorption, FTT, calcium deficiency if not appropriately supplemented
What is the prognosis of lactose intolerance?
Congenital is lifelong, primary is variable, secondary is transient
