Description

• Malabsorption syndrome (MAS) of unknown/infectious etiology occurring primarily in patients in the tropics and subtropics: diagnosis likely if (1):
  • Typical clinical presentation
  • Deficiency of two nutrients
  • Abnormal small intestinal mucosal histology
  • Exclusion of other specific causes for MAS
  • Persistent response to treatment with antibiotics
• Symptoms may appear years after leaving an endemic area and may be relapsing without treatment.
• Endemic areas: tropic regions only—India, Southeast Asia, and Caribbean. Distribution is sporadic.
• System(s) affected: gastrointestinal, hematologic, lymphatic, immunologic

Epidemiology

Incidence

• Predominant sex: male = female
• Rarely fatal but can be unremitting

Risk Factors

• Infectious source likely (viruses, parasites, or bacteria)
• Indigenous populations in endemic tropical countries
• Travelers spending at least 1 month in high-risk endemic areas; symptoms may develop years after returning.

Etiology and Pathophysiology

• Multifactorial-possible infectious agent, including persistent overgrowth of the small intestine by enteric pathogens after a bout of traveler’s diarrhea
• Invasive pathogens cause enterocyte damage in the small intestine, which leads to an increase in enteroglucagon and other intestinal hormones, leading to increase in small intestinal stasis and further bacterial colonization. Villous atrophy results in impaired absorption of carbohydrates, fat, folate, iron, and vitamin B_12.
• Dietary deficiency (folate and vitamin B₁₂) possibly further disrupts structural integrity of the small intestine.