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What is Tropical sprue and explain in detail?
Tropical sprue is a malabsorption disease commonly found in tropical regions, marked with abnormal flattening of the villi and inflammation of the lining of the small intestine. It differs significantly from coeliac sprue. It appears to be a more severe form of environmental enteropathy.

Signs and symptoms
The illness usually starts with an attack of acute diarrhoea, fever and malaise following which, after a variable period, the patient settles into the chronic phase of diarrhoea, steatorrhoea, weight loss, anorexia, malaise, and nutritional deficiencies.
The symptoms of tropical sprue are:

Diarrhoea
Steatorrhoea or fatty stool (often foul-smelling and whitish in colour)
Indigestion
Cramps
Weight loss and malnutrition
FatigueLeft untreated, nutrient and vitamin deficiencies may develop in patients with tropical sprue.  These deficiencies may have these symptoms:

Vitamin A deficiency: hyperkeratosis or skin scales
Vitamin B12 and folic acid deficiencies: anaemia, numbness, and tingling sensation
Vitamin D and calcium deficiencies: spasm, bone pain, muscle weakness
Vitamin K deficiency: bruises

Cause
The cause of tropical sprue is not known.  It may be caused by persistent bacterial, viral, amoebal, or parasitic infections.  Folic acid deficiency, effects of malabsorbed fat on intestinal motility, and persistent small intestinal bacterial overgrowth may combine to cause the disorder. A link between small intestinal bacterial overgrowth and tropical sprue has been proposed to be involved in the aetiology of post-infectious irritable bowel syndrome (IBS). Intestinal immunologic dysfunction, including deficiencies in secretory immunoglobulin A (IgA), may predispose people to malabsorption and bacterial colonization, so tropical sprue may be triggered in susceptible individuals following an acute enteric infection.

Diagnosis
Diagnosis of tropical sprue can be complicated because many diseases have similar symptoms.  The following investigation results are suggestive:
Abnormal flattening of villi and inflammation of the lining of the small intestine, observed during an endoscopic procedure.
Presence of inflammatory cells (most often lymphocytes) in the biopsy of small intestine tissue.
Low levels of vitamins A, B12, E, D, and K, as well as serum albumin, calcium, and folate, revealed by a blood test.
Excess fat in the feces (steatorrhoea).
Thickened small bowel folds seen on imaging.Tropical sprue is largely limited to within about 30 degrees north and south of the equator.  Recent travel to this region is a key factor in diagnosing this disease in residents of countries outside of that geographical region.Other conditions which can resemble tropical sprue need to be differentiated.  Coeliac disease (also known as coeliac sprue or gluten sensitive enteropathy), has similar symptoms to tropical sprue, with the flattening of the villi and small intestine inflammation and is caused by an autoimmune disorder in genetically susceptible individuals triggered by ingested gluten.  Malabsorption can also be caused by protozoan infections, tuberculosis, HIV/AIDS, immunodeficiency, chronic pancreatitis and inflammatory bowel disease