Anne Mitchell sensed something was not quite right when the fetus in her first pregnancy did not move as she had been told to expect.  When her son Michael was born, he was extremely hypotonic and weak, requiring immediate intubation and a trip to the NICU.  Without any family history of similar issues, Anne and David Mitchell did not have any idea why Michael’s muscles were so weak.  After various tests all came back negative, Michael had a muscle biopsy at 4 weeks of age and was diagnosed with centronuclear myopathy.  

Centronuclear myopathy (CNM) is an umbrella term for a group of related hereditary congenital myopathies characterized by variable muscle weakness and hypotonia with onset from birth through adulthood.  Intelligence and cardiac muscles are generally not affected.  Mutations in the MTM1, DNM2, RYR1, and BIN1 genes have been associated with different forms of CNM, including X-linked, dominant, and recessive inheritance patterns.  MTM1 mutations are associated with a specific form of CNM called X-linked myotubular myopathy (XLMTM), which generally causes infantile onset of severe muscle weakness that often leads to feeding and respiratory issues. 

Given Michael’s early onset of weakness, MTM1 testing was ordered through the University of Chicago Genetic Services Laboratory, and the results confirmed that Michael had an MTM1 mutation and XLMTM.  Although it was hard for Anne and David to hear the results, they also found it helpful and reassuring to know the definite diagnosis.  The diagnosis gave the Mitchell family a sense of identity to embrace and empowered them to seek out medical specialists and experts, including the Beggs Congenital Myopathy Research Program at Children’s Hospital in Boston.   Most importantly, Michael and his family were able to connect with other families and become a part of the broader XLMTM community. 

Carrier testing confirmed that Anne was a carrier of the MTM1 mutation, as seen in more than 80% of XLMTM mothers.  Although it was not a determining factor in their family planning, Anne and David found the information helpful, particularly for sharing with family members.  Anne’s mother was not a carrier, suggesting that the mutation was de novo.  Given the risk of germline mosaicism, Anne’s sister also pursued testing and was found not to be a carrier.

After spending the first three months of his life in the neonatal ICU, Michael was transferred to a rehabilitation center for a brief stay and then transitioned home at four months of age to live with his parents.  Michael is now 10 years old and is in the 4th grade.  He uses a wheelchair and requires 24-hour respiratory support, but he and his parents do not let this limit him.  He loves sports, animals, going to school, and spending time with his family.  

Names and other identifying information have been changed in order to protect this family’s privacy.