Information on the following diseases can be found in the Related Disorders section of this report:

• Lactose Intolerance
• Familial Chloride Diarrhea
• Infantile Diarrhea With Abnormal Hair
• Congenital Sodium Diarrhea

Microvillus inclusion disease is characterized by severe, large amounts of watery diarrhea appearing at birth or within seventy-two hours. Symptoms of a rare late onset form may not occur until two or three months after birth. Diarrhea persists even after oral feeding is stopped and does not decrease with age. Diarrhea often worsens after feeding because of insufficient absorption (malabsorption) of necessary nutrients. The diarrhea often results in life-threatening complications, specifically severe dehydration and metabolic acidosis, which may cause kidney failure, requiring the infant to be hospitalized. There may also be related weight loss, growth retardation and developmental delay.

Infants affected by this disorder require total intravenous hydration and total parenteral nutrition (TPN). TPN may be associated with an increased risk of developing blockage of the liver or bile ducts preventing the normal flow of bile (cholestasis) and liver failure.

Microvillus inclusion disease is thought to be caused by a basic defect in the cells in the intestinal wall of the small intestine and colon. Some researchers believe that it is inherited as an autosomal recessive trait. The specific genetic mutation involved has not yet been identified.

Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother. Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females.

All individuals carry a few abnormal genes. Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.

Fewer than 100 cases of microvillus inclusion disease had been reported in the medical literature. The true prevalence of this disorder is unknown. Most cases become apparent soon after birth, but it is also believed by some that there is a later-onset form that becomes apparent six to eight weeks after birth in infants that, until then, have appeared healthy. Microvillus inclusion disease affects more females than males with a sex ratio of about 2:1.

Microvillus inclusion disease was first described in the medical literature in 1978.

Symptoms of the following disorders can be similar to those of microvillus inclusion disease. Comparisons may be useful for a differential diagnosis:

Lactose intolerance is a malabsorption syndrome that results from impaired absorption of a sugar found in milk (lactose). This nutrient is normally absorbed in the small bowel. Lactose intolerance is characterized by diarrhea and abdominal distention causing stomach pain and gas (flatulence) that occurs after drinking milk. A lack of one or more intestinal enzymes results in an inability to digest certain carbohydrates. Lactase, maltase, isomaltase, and sucrase usually split complex sugars into simple sugars. In patients with lactose intolerance, the enzyme, lactase, which digests this sugar in the small bowel, is lacking. (For more information on this disorder, choose "Lactose" as your search term in the Rare Disease Database.)

Familial chloride diarrhea is a malabsorption syndrome of autosomal recessive inheritance. This disorder is apparent during the first few weeks of life and is characterized by an abnormally large number of watery stools containing an excess of chloride. Infants born with this disorder are often premature.

Infantile diarrhea with abnormal hair is another malabsorption syndrome of autosomal recessive inheritance. The disorder usually develops around the third week of life with a rapidly progressive course. It is characterized by severe unexplained diarrhea, low birth weight and large, low-set, simple ears, flat nasal bridge, and large mouth. Black, kinky hair that easily falls out and a lack of normal amino acids is another feature of this syndrome.

Soy protein intolerant infants are allergic to soy proteins. Often, they are allergic, not only to soy, but to many other foods. They have complex nutritional problems and should be distinguished from those with sensitivity to common food proteins such as cow's milk, egg and peanuts.

Congenital sodium diarrhea is inherited as a recessive genetic trait. It occurs as a result of a defective sodium exchange in the bowels. The disorder is usually present at birth and is characterized by profuse watery diarrhea and a swollen abdomen.

Diagnosis
The diagnosis of microvillus inclusion disease may be based upon electron microscopy of a tissue sample (biopsy) from the intestine of an ailing child, which depicts microscopic findings characteristic of the disorder. Before a biopsy is performed, other causes of dehydration and diarrhea in infants are ruled out.

Treatment
No effective drug treatment is available. Treatment of microvillus inclusion disease is accomplished through intravenous feeding often called total parenteral nutrition (TPN). .

However, chronic TPN carries with it high risks of infection (sepsis), liver damage and other organ disorders. Therefore, the affected child must be carefully monitored by a physician.

Some children with severe disease have been treated with transplantation of a part of the small intestine.

Other treatment of microvillus inclusion disease is symptomatic and supportive. Genetic counseling will be of benefit for affected individuals and their families.

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.

For information about clinical trials being conducted at the National Institutes of Health (NIH) Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: prpl@cc.nih.gov

McKusick VA, ed. Online Mendelian Inheritance In Man (OMIM). The Johns Hopkins University. Microvillus Inclusion Disease. Entry Number; 251850: Last Edit Date; 3/17/2004.

TEXTBOOKS
Kennea NL. Microvillus Inclusion Disease. In: NORD Guide to Rare Disorders. Lippincott Williams & Wilkins. Philadelphia, PA. 2003:351.

Behrman RE, Kliegman RM, Arvin AM., eds. Nelson Textbook of Pediatrics. 15th ed. W.B. Saunder Company. Philadelphia, PA; 1996:1097.

Yamada T, Alpers DH, Owyang C, et al., eds. Textbook of Gastroenterology. 2nd ed. J. B. Lippincott Company. Philadephia, PA; 1995:1669.

REVIEW ARTICLES
Ruemmele FM, Schmitz J, Goulet O. Microvillus inclusion disease (microvillus atrophy). Orphanet J Rare Dis. 2006;1:22.

Sherman PM, Mitchell DJ, Cutz E. Neonatal enteropathies: defining the causes of protracted diarrhea of infancy. J Pediatr Gastroenterol Nutr. 2004;38:16-26.

Mehta DI, Blecker U. Chronic diarrhea in infancy and childhood. J La State Med Soc. 1998;150:419-29.

JOURNAL ARTICLES
Ruemmele FM, Jan D, Lacaille F, et al. New perspectives for children with microvillus inclusion disease: early small bowel transplantation. Transplantation. 2004;77:1024-28.

Goulet O, Ruemmele F, Lacaille F, et al. Irreversible intestinal failure. J Pediatr Gastroenterol Nutr. 2004;38:250-69.

Gambarara M, Diamanti A, Ferretti F, et al. Intractable diarrhea of infancy with congenital intestinal mucosa abnormalities: outcome of four cases. Transplant Proc. 2003;35:3052-53.

Hasegawa T, Sasaki T, Kimura T, et al. Effects of isolated small bowel transplantation on liver dysfunction caused by intestinal failure and long term total parenteral nutrition. Pediatr Transplant. 2002;6:235-39.

Kennea N, Norbury R, Anderson G, et al. Congenital microvillus inclusion disease presenting as antenatal bowel obstruction. Ultrasound Obstet Gynecol. 2001;17:172-74.

Oliva MM, Perman JA, Saavedra JM, et al. Successful intestinal transplantation for microvillus inclusion disease. Gastroenterology. 1994;106:771-74.

FROM THE INTERNET
Guandalini S, Nocerino A. Congenital Microvillus Atrophy. emedicine. Last Updated: May 25, 2002.
www.emedicine.com/PED/topic461.htm

Greenstein SM, Prowse O. Intestinal Transplantation. emedicine. Last Updated: August 12, 2004.
www.emedicine.com/ped/topic2845/htm

The Salas Laboratory: Epithelial cell polarity and beyond. nd. 3pp.
http://chroma.med.miami.edu/cellbio/Salas/