This is a rare genetic intestinal disorder mostly evident within hours from the birth of the infant. Microvillus inclusion disease causes malabsorption of essential nutrients as the result of incomplete development and the degeneration of cells in the small intestine. In rare cases, diarrhea associated with this disease starts around the age of 3 or 4 months of age. In addition to the symptoms of this condition, the affected infants can also present the reduced ability to produce the digestive juice called bile which can cause irreversible liver disease (cirrhosis). Most of the affected children are not able to survive beyond childhood even with the nutritional supplement.
Causes
Microvillus inclusion disease develops as the result of a mutation in the gene MY05B which produces a protein known as myosin Vb which determines the location of components within cells. This protein is also essential for the transportation of components from the cell membranes for recycling. The genetic mutation results in the deficit or the lack of myosin Vb function. Hence the cells that line the small intestine cannot form the structure called microvilli which is responsible for the absorption of nutrients from the food that we consume. The poorly developed microvilli cannot effectively absorb the nutrients and this inability causes the symptoms associated with this condition. This disease is inherited in an autosomal recessive pattern meaning both the copies of the gene in each cell are defective. The parents of the affected individual do not necessarily exhibit the symptoms associated with this condition.
Symptoms
The affected infant will present severe, watery diarrhea that usually does not go away and the inability to absorb the nutrients. With the insufficient nutrients and fluids, they can become severely dehydrated, unable to gain weight and grow normally. In addition, they can also develop kidney problems, thinning of the bones (osteoporosis), developmental delays and kidney problems.
Diagnosis
The initial diagnosis can involve testing the child’s bowel for levels of various nutrients that normally would not be absorbed as the result of this condition. The only effective diagnosis of this disease is based on the examination of the tissue sample that detects the characteristic findings of the disorder such as the distinct difference in the cells of the small intestine. Various diagnostic tests may also be required to rule out possible conditions that present dehydration and diarrhea. The genetic test can identify the mutation responsible for the development of this condition.
Treatment
There is no cure for microvillus inclusion disease and the treatment is based on the intravenous feeding called total parenteral nutrition. As the affected individuals are at increased risk of developing complications such as infection (sepsis), liver damage and other organ problems, they must be carefully monitored. The severe cases have been treated with the transplantation of a part of the small intestine. In some cases, the genetic counseling can be beneficial for the affected individuals and their families.
References
https://ghr.nlm.nih.gov/condition/microvillus-inclusion-disease#inheritance
https://rarediseases.org/rare-diseases/microvillus-inclusion-disease/
