An Overview of Megacystis Microcolon Intestinal Hypoperistalsis Syndrome (MMIHS)

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Megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS) is a rare congenital condition that results from a developmental defect of the smooth muscle in the bladder and colon. This impairs the functioning of the stomach, intestines, kidneys, and bladder, thus interfering with urination and digestion. It can cause vomiting and abdominal distension (enlargement) in affected newborns, and children diagnosed with MMIHS require significant, ongoing supportive care.

MMIHS is a lifelong condition and, unfortunately, there is no cure. Life expectancy for those with the condition can be as short as one year, though longer survival—even into adulthood—is possible when a case is mild.

Also Known As

Megacystis microcolon intestinal hypoperistalsis syndrome is also referred to as MMIH syndrome and Berdon syndrome.

Symptoms

The severity of MMIHS ranges. The effects typically cause immediate distress within a few hours after birth.

Symptoms of MMIH syndrome in a newborn include:

  • Minimal urine output or a complete lack of urination
  • Flabby appearing abdominal muscles
  • A wrinkled appearing abdomen
  • Abdominal distension
  • Vomiting, which can have a green tinge
  • Lack of meconium (a baby's first bowel movement, which is usually passed within the hour after birth)

Babies who have MMIHS may be in discomfort, which can cause persistent, inconsolable crying.

Some baby boys with MMIHS have undescended testes, though this is not uncommon in healthy baby boys—especially those who are born before full term.

Complications

Given the lifelong nature of MMIHS and its effect on major organs, several complications can occur.

Intestinal Problems

Smooth muscle (that which lines internal organs) in the digestive system normally works via peristalsis—a rhythmic, involuntary contraction (activation) and relaxation that moves digested food forward from the stomach to the small intestine for the absorption of nutrients. The undigested waste material moves to the colon (large intestine) and is eventually released from the rectum as stool.

With MMIHS, the gastrointestinal smooth muscles do not move as they should, resulting in narrowing of the lumen (opening) of the intestines. This makes it harder for food and stool to pass through.

Bladder Problems

The smooth muscles of the bladder do not function as they should in MMIHS. This is what interferes with the flow of urine and causes a buildup of urine in the bladder.

Hydronephrosis, which is the backflow of urine into the kidneys, may result as well.

Long-Term Effects

As children get older, they will continue to experience the effects of MMIHS, even with treatment.

Issues that someone with megacystis microcolon intestinal hypoperistalsis syndrome may encounter, due to either weakened intestinal or bladder muscles, include:

  • A lack of appetite
  • Vomiting
  • Abdominal discomfort
  • Abdominal distension
  • Weight loss
  • Diminished urination

Cause

The smooth muscles of the bladder and intestines begin to malform in utero as a fetus with MMIH syndrome develops. There are a variety of genes and hereditary patterns associated with MMIHS. That said, it can also occur without a known genetic cause. It is not clear why some people have a milder version of MMIHA, while others are severely affected by it.

Several genetic defects have been described in association with this condition, including changes in the ACTG2, MYH11, or LMOD1 genes. These genes are involved in coding for the formation of smooth muscle.

Experts suggest that the hereditary pattern of the ACTG2 gene is autosomal dominant. This means that if a person inherits the disease-producing gene from one parent, they will develop the disease.

The other genes associated with MMIHS are inherited in an autosomal recessive pattern. This means that a person would have to inherit the disease-producing gene from both parents to develop the disease.

In rare instances, a baby can develop one of these mutations without inheriting it.

Diagnosis

MMIHS is usually diagnosed based on a baby's symptoms, physical examination, and diagnostic testing. Sometimes the bladder and intestinal problems can be detected in utero.

Note, however, that MMIHS is a rare disease that has been identified in fewer than 200 families. Because of this, it can take months to confirm a diagnosis. Your child's doctor will work to rule another cause of digestive, intestinal, or bladder problems during this process.

Fetal Testing

If your family has a history of MMIHS, this will alert your medical team to search for evidence of the condition on your baby's prenatal ultrasound imaging.

An enlarged bladder or intestinal muscle problems may be seen on fetal ultrasound. A fetal urine test can identify abnormalities associated with this disorder as well.

Physical Examination

Babies are routinely examined immediately after birth. Passing meconium (pooping) is one of the early things that the medical team looks for when a baby is born. Babies are not typically sent home with parents until they have had a bowel movement, eaten, and produced urine.

If your baby does not have these three indicators of good health, they will probably need a medical evaluation.

MMIHS is also associated with heart and other internal organ problems, so your child's doctor may search for other developmental issues as part of the diagnostic evaluation.

MMIHS can be mistaken for prune belly syndrome, which is a rare condition characterized by congenital kidney problems.

Imaging Tests

If your newborn baby has risk factors or signs of MMIHS, they may need a pelvic and abdominal ultrasound or computerized tomography (CT) for visualization of the bladder and intestines.

Imaging tests may show signs of:

  • Microcolon (a very small appearing colon)
  • Enlargement of the small intestine or stomach
  • Twisting or malrotation of the intestines
  • An enlarged bladder
  • Malformations of the urinary tract
  • Hydronephrosis
  • Enlarged ureters (the tubes that send urine from the kidneys to the bladder)
  • Undescended testes

Genetic Testing

When physical characteristics of MMIHS are present, your baby and their siblings, as well as biological parents, may be tested for the genetic mutations. If family members have the gene, this can help in family planning.

Treatment

Living with MMIHS is difficult. Children may become malnourished and typically need nutritional support. Procedures such as catheterization (placement of a tube in the body) can help prevent kidney and digestive complications. In some instances, organ transplantation may improve survival.

Nutrition Interventions

There are several approaches that are aimed at providing nutrition to those with MMHIS. Infants typically receive IV fluids and nutrients, but this type of nutritional supplementation generally does not provide enough calories and nutrients for long-term survival.

People who have mild disease may require nutritional supplements as well.

Procedures

In some instances, a surgical ileostomy of the small intestine is necessary. This is an opening in the abdominal wall that allows undigested material to be directly emptied into a bag outside the body instead of going through the colon.

A catheter may be placed in the urethra (the structure from which urine passes from the bladder to the outside of the body) to aid with urination. In some instances, a tube may be surgically placed in the bladder to release urine directly into a bag, bypassing the urethra.

Transplant Surgery

There have been children who received multiple organ transplants for the treatment of MMIHS with varying degrees of success . Intestinal transplants may involve attaching a small or large region of a donor's intestine with the goal of providing the affected child with the normal movement of intestinal smooth muscles.

A Word From Verywell

The effects of MMIHS are severe, necessitating extensive medical and surgical care. Survival is improving as treatment approaches have advanced. If your child has a rare condition, be sure to reach out for help from medical professionals and support groups who can help you cope with the stress of caring for a child with extensive healthcare needs.

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Article Sources

  1. Korğalı EÜ, Yavuz A, Şimşek CEÇ, Güney C, Kurtulgan HK, Başer B et al. Megacystis Microcolon Intestinal Hypoperistalsis Syndrome in Which a Different De Novo Actg2 Gene Mutation was Detected: A Case Report. Fetal Pediatr Pathol. 2018 Apr;37(2):109-116. doi: 10.1080/15513815.2018.1445149. Epub 2018 Apr 2.

  2. U.S. National Library of Medicine, Genetics Home Reference, Megacystis-microcolon-intestinal hypoperistalsis syndrome 

  3. Rosenblatt J, Dreux S, Spaggiari E, Morin C, Allaf B, Valat AS. Prenatal diagnosis of megacystis microcolon intestinal hypoperistalsis syndrome by biochemical analysis of fetal urine. Prenat Diagn. 2018 May 12. doi: 10.1002/pd.5283. [Epub ahead of print]

  4. Gosemann JH, Puri P. Megacystis microcolon intestinal hypoperistalsis syndrome: systematic review of outcome. Pediatr Surg Int. 2011 Oct;27(10):1041-6. doi: 10.1007/s00383-011-2954-9.

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