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.

Epidemiology

• 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.

Aetiology

• 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.

Presentation

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

Investigations

• 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 25 g xylose is given by mouth and normal results are that urine contains at least 20 mg per 100 ml at 1 hour and a total of 4 g excreted in 5 hours. Lower results suggest malabsorption.
• Faecal fat measures: patients are fed a diet with high fat over 72 hours (80 to 100 g per day). A faecal fat exceeding 6 g a day is abnormal but steatorrhoea usually requires at least 15 g a day.
• Jejunal biopsy - this shows incomplete villous atrophy (as opposed to coeliac's where there is complete villous atrophy).¹

Differential diagnosis

• Secondary malabsorption due to protozoal (e.g. giardial), 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

Complications

• 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 utilisation 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.

Management

• 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 - for example:
  • 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.

Monitoring treatment

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

Prognosis

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

Prevention

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

Document references

1. Ramakrishna BS, Venkataraman S, Mukhopadhya A; Tropical malabsorption. Postgrad Med J. 2006 Dec;82(974):779-87. [abstract]
2. Haghighi P, Wolf PL; Tropical sprue and subclinical enteropathy: a vision for the nineties. Crit Rev Clin Lab Sci. 1997 Aug;34(4):313-41. [abstract]
3. Thielman NM, Guerrant RL; Persistent diarrhea in the returned traveler. Infect Dis Clin North Am. 1998 Jun;12(2):489-501. [abstract]
4. Bhatnagar S, Gupta SD, Mathur M, et al; Celiac disease with mild to moderate histologic changes is a common cause of chronic diarrhea in Indian children. J Pediatr Gastroenterol Nutr. 2005 Aug;41(2):204-9. [abstract]
5. Baqai MT; Duodenal tuberculosis: delays and difficulties in diagnosis. J R Coll Physicians Edinb 2005; 35:330-331
6. Westergaard H; Tropical Sprue. Curr Treat Options Gastroenterol. 2004 Feb;7(1):7-11. [abstract]
7. Tomkins AM, Smith T, Wright SG; Assessment of early and delayed responses in vitamin B12 absorption during antibiotic therapy in tropical malabsorption. Clin Sci Mol Med Suppl. 1978 Dec;55(6):533-9. [abstract]
8. Klipstein FA, Corcino JJ; Factors responsible for weight loss in tropical sprue. Am J Clin Nutr. 1977 Oct;30(10):1703-8. [abstract]

Acknowledgements