Tropical Sprue

Synonyms: Postinfective tropical malabsorption, idiopathic tropical malabsorption syndrome

• Diarrhoea
• Malabsorption
• Weight loss

It is to be distinguished from tropical enteropathy, an asymptomatic condition, defined by mild histological changes in the intestinal mucosa, which coexists in endemic areas and is probably an adaption to environmental factors.

• Tropical sprue usually occurs in residents of tropical or subtropical climates (less commonly visitors), usually in developing countries.
• The incidence varies considerably with geography.
• It occurs mostly in south-east Asia and the Caribbean but not in Jamaica.¹
• The incidence is high in Puerto Rico but low in southern Africa.
• There is no predilection for race or gender.
• It tends to affect adults but can also occur in children.
• The condition may present in natives or travellers and may not present until after they have left the area. The lag can be up to 10 years.

• The aetiology is presumed to be infective but the exact cause remains elusive.
• The exact nature of the infection, whether initiated or perpetuated by enterotoxic coliform bacteria, viruses or a combination of pathogens, is not clear.²
• Usually just the upper small intestine is affected but more rarely the stomach or colon may be involved.

It may range in severity from subclinical structural or functional deficiencies of the gastrointestinal mucosa to a full picture of malabsorption with diarrhoea, malnutrition and loss of weight. The clinical picture can be variable and incomplete and may include:

• Diarrhoea (acute or chronic)
• Weight loss
• Malabsorption - deficiency of the following may occur:
  • Iron, folate and vitamin B12 - are the most common and there may be signs such as, pallor or glossitis
  • Vitamin A deficiency - with hyperkeratosis
  • Vitamin D and calcium deficiency - may cause abdominal pain, bone pain etc
  • Vitamin K deficiency - risk of prolonged INR and haemorrhage
• Abdominal pain - may be mild and does not usually dominate the clinical picture
• Ankle oedema (hypoalbuminaemia)
• Fatigue
• Fever
• Steatorrhoea

• FBC - macrocytic anaemia with low folate and vitamin B12 levels in 60%.
• Malabsorption and diarrhoea - may produce low levels of potassium, iron and albumin.
• Calcium and phosphate may be abnormal, especially with low albumin.
• Malabsorption of D-xylose: ensure normal renal function. A dose of 25g xylose is given by mouth and normal results are that urine contains at least 20mg per 100ml at 1 hour and a total of 4g excreted in 5 hours. Lower results suggest malabsorption.
• Faecal fat measures: patients are fed a diet with high fat over 72 hours (80 to 100g per day). A faecal fat exceeding 6g a day is abnormal but steatorrhoea usually requires at least 15g a day.
• Jejunal biopsy - this shows incomplete villous atrophy (as opposed to coeliac's where there is complete villous atrophy).¹

• Secondary malabsorption due to protozoal (e.g. Giardiasis), helminthic, bacterial, or viral infections³
• Coeliac disease, especially when children are affected⁴
• Crohn's disease
• Tuberculosis of the gut can occur without pulmonary manifestations⁵
• Disease of the pancreas
• AIDS enteropathy

• If vitamin B12 levels are very low, replacement must start before folate or the demands of the haemopoietic system may precipitate subacute combined degeneration of the cord.
• Potassium supplements may also be needed as rapid utilization occurs when haemaopotiesis starts. Failure to do so may account for the occasional sudden death seen at the start of treatment for severe B12 deficiency.

• Fluid resuscitation
• Antibiotics - tetracycline is most often used and prolonged periods of treatment are necessary e.g. 6-12 months.⁶ However, some patients in southern India respond poorly to antibiotics.
• Nutritional supplements e.g.
  • Folic acid - may need to be given parenterally at first if absorption is poor.
  • Vitamin B12 injections - given daily for 5 to 10 days and then once a month. Absorption of vitamin B12 recovers early and so deficiency may be due to bacterial action rather than malabsorption.⁷
  • Oral iron may also be required but iron and tetracycline should not be taken close to each other as the tetracycline chelates the iron and neither is absorbed.

Treatment is monitored by

• Symptom improvement e.g. disappearance of anorexia with adequate B12 and folate replacement⁸
• Weight gain
• Improvement of FBC and biochemical parameters

Untreated disease runs a chronic, relapsing course. However, treatment is associated with a good prognosis.

There is no established way to prevent the disease whilst visiting areas of risk.