Holocarboxylase Synthetase Deficience (also known as early-onset multiple carboxylase deficiency, MCD)


Holocarboxylase synthetase deficiency (also known as early-onset multiple carboxylase deficiency or MCD) is an inborn error of metabolism, an inherited condition in which an enzyme, holocarboxylase synthetase, in the body is either missing or not working well. The job of this enzyme is to help attach the vitamin biotin to other enzymes known as carboxylases. When the holocarboxylase synthetase enzyme is missing or not working well, the carboxylase enzymes cannot properly process nutrients and cells in the body cannot function well. Holocarboxylase synthetase deficiency is an organic acid condition because it can lead to a harmful buildup of organic acids and toxins in the body. Signs of holocarboxylase synthetase deficiency may include skin rashes, hair loss, extreme tiredness/lethargy, vomiting, irritability, breathing problems, changes in muscle tone, developmental delay, ataxia (problems with muscle control during movement), seizures and/or other potential signs and symptoms. If holocarboxylase synthetase deficiency is not treated, it can be life-threatening. Early detection and prompt and ongoing management treatment can benefit children living with this condition. Support groups are available to help connect families living with holocarboxylase synthetase deficiency with others who have experience or expertise with this condition.

To learn more about Multiple carboxylase deficiency, visit Baby's First Test: Holocarboxylase synthetase deficiency and Screening, Technology, and Research in Genetics (STAR-G): holocarboxylase synthetase deficiency. Please see Medically Prescribed Formula for information about medically prescribed formula and pharmacologic interventions for inborn errors of metabolism. A listing of contact information for Minnesota inborn errors of metabolism medical specialty providers/clinics serving children affected with or undergoing evaluation for conditions that can be detected through Minnesota Newborn Screening is available upon request.