It is not known how MOMO syndrome is inherited. It was originally thought that MOMO syndrome is inherited in an autosomal dominant manner. This means that only one copy of the gene that causes MOMO syndrome needs to be changed in order for a person to show signs of the syndrome. We inherit one copy of each gene from our mother and the other from our father.

Autosomal dominant inheritance was originally suspected because each of the reported cases of MOMO syndrome have only occurred once in a family, and the person with MOMO syndrome has been born to healthy parents. When only one person in a family is affected with a particular genetic syndrome, autosomal dominant inheritance is a possible explanation because the genetic change (mutation) in only one copy of the gene may be new (de novo) in the person who has the syndrome. Therefore, one possible explanation is that each case of MOMO syndrome that is reported occurred when a new genetic change happened by chance when each affected individual was conceived.

If MOMO syndrome is inherited in an autosomal dominant manner, it occurs by chance, and it is very unlikely for two parents who have a child with MOMO syndrome to have another child with MOMO syndrome. An individual with MOMO syndrome has not been known to have children. However, if this were to happen, each child would have a 50% chance to inherit MOMO syndrome as well.

In one case, a person with MOMO syndrome was found to have a genetic change in the LINC00237 gene. In this case, a new inheritance pattern, called autosomal recessive inheritance, was suspected. Autosomal recessive inheritance occurs when both copies of the same gene have changes that cause them not to work properly. In the individual with MOMO syndrome who had changes in the LINC00237 gene, both copies of the gene were not functioning correctly, which caused some researchers to suspect that MOMO syndrome may be inherited in an autosomal recessive manner.

If MOMO syndrome is inherited in an autosomal recessive manner, it means that both parents of an individual with the syndrome would have a genetic change in only one of the copies of the gene that causes the syndrome. This means they would be carriers of MOMO syndrome. If this were the case, when two carriers of MOMO syndrome have children together, for each child there would be a:

• 25% chance that the child will have MOMO syndrome
• 50% chance that the child will be a carrier of MOMO syndrome like the parents
• 25% chance that the child will have two working copies of the gene, so the child will not have MOMO syndrome and will not be a carrier

It is important to remember that we do not know for sure how MOMO syndrome is inherited. Therefore, the exact chance that parents who have a child with MOMO syndrome could have another affected child is uncertain.