What are CDD (Congenital Diarrheal Disorders)

Congenital diarrheal disorders are rare genetic disorders that usually occur during the first week of life. Affected infants may have frequent chronic diarrhea, malabsorption, feeding intolerance, and retarded growth. For most congenital diarrheal disorders, the disease-causing gene is identified.

Some examples of congenital diarrheal disorders, along with the gene mutation involved, are given below.

Congenital chloride diarrhea – SLC26A3 gene.

Congenital sodium diarrhea – SPLINT2, GUCY2C, and SLC9A3 gene.

Microvillus inclusion disease – MYO5B, STXBP2, and STX3.

Congenital tufting enteropathy – EPCAM (epithelial cell adhesion molecule).

Congenital malabsorptive diarrhea – NEUROG 3.

Source: https://www.icliniq.com/articles/newborn-and-baby/congenital-sodium-diarrhea

What is MVID (Microvillous Inclusion Disease)

Microvillus Inclusion Disease (MVID) is a CDD and was first described by Davidson and colleagues in 1978 (Davidson, 1978). Since 1978, fewer than 200 cases have been published in the literature. MVID is an ultra-rare, congenital diarrheal disorder (CDD) that represents one form of pediatric intestinal failure (Duggan, 2017).

MVID is caused by changes (mutations) in a gene called MYO5B [(Kalashyan, 2023; Müller, 2008; van der Velde, 2013; Bowman, 2022; Babcock, 2022; Erickson, 2008)]. This gene normally helps certain proteins reach the surface of the cells lining the intestine, where they play an important role in absorbing nutrients and fluids. When the MYO5B gene doesn’t work properly, the surface of these cells doesn’t develop as it should, leading to a poorly formed intestinal lining (Kalashyan, 2023).

In general, patients with MVID and severe loss of MYO5B function develop severe diarrhea in the first days of life. Their intestines can’t absorb fluids or nutrients properly, so they lose a lot of water and essential substances. To survive and grow, these infants usually need intravenous (parenteral) nutrition and extra fluids, since their bodies can’t take in enough from regular feeding [(Babcock, 2022; Ruemmele, 2006)]. No effective drug treatment is available for MVID patients.

What is SBS (Short Bowel Syndrome)

Short bowel syndrome is a type of intestinal failure that happens when a person has too little functioning small intestine to absorb enough nutrients and fluids. This can be caused by a birth defect, intestinal damage from poor blood flow (infarction), or surgical removal of a large portion of the intestine.

Source (https://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=EN&Expert=79280).

SBS is generally defined as having less than 75 cm of small intestine in children, or less than 200 cm in adults, with the colon excluded from the measurement (Guillen, 2022).

No matter the cause, losing a large portion of the intestine limits the body’s ability to adapt, often leading to severe diarrhea, malnutrition, dehydration, and fluid and salt imbalances (Schalamon, 2003). Most patients with SBS struggle with debilitating diarrhea, which can significantly affect their overall health and quality of life (Kumpf, 2014).