Medical foods for patients with rare IEMs may cause harm when not carefully managed

Many medical foods are designed to help manage patients with rare inborn errors of metabolism (IEMs), and can help prevent serious and life-threatening complications. However, such special foods may cause harm in some patients when their use is not carefully monitored and managed, according to a research team led by scientists at the National Human Genome Research Institute (NHGRI), part of the National Institutes of Health. The researchers contend that there is a need for more rigorous clinical study of dietary management practices for patients with IEMs, including any associated long-term side effects, which may in turn result in the need to reformulate some medical foods.
In two studies appearing online August 13, 2015 and in the August issue of Genetics in Medicine, the researchers noted that medical foods, including those given to patients with methylmalonic acidemia (MMA), are not subject to the same scrutiny as therapeutic drugs. A medical food, as defined in the Orphan Drug Act, is regulated as a food by the Food and Drug Administration and intended to be used under medical supervision.
The researchers based their conclusions on more than 10 years of observational studies with large patient groups involving two inborn errors of metabolism. The two IEMs studied are rare genetic disorders in which the body cannot properly turn food into energy. In the first of these, known as isolated methylmalonic acidemia (MMA), mutations in any one of four genes can impede enzyme activity that is necessary for the proper breakdown of amino acids, the building blocks of proteins (specifically the amino acids valine, isoleucine, methionine and threonine). In the other, cobalamin C (cblC) type combined MMA and hyper-homocysteinemia, failure to properly process vitamin B12 results in a different form of MMA that clinically looks different and requires different management.